S Designations —See supports for gas chromatography in the Chromatographic Reagentssection under Chromatography á621ñ.

Saccharose —Use Sucrose(NFmonograph).

Safranin O —Dark red powder consisting of a mixture of 3,7-diamino-2,8-dimethyl-5-phenylphenazinium chloride,C20H19ClN4—350.85,and 3,7-diamino-2,8-dimethyl-5-o-tolylphenazinium chloride,C21H21ClN4—364.88—Sparingly soluble in 70percent alcohol yielding a clear red solution with a yellowish-red fluorescence.
Identification—
A: To 10mLof a 0.5%w/v solution add 5mLof hydrochloric acid:a bluish violet solution is produced.
B: To 10mLof a 0.5%w/v solution add 5mLof sodium hydroxide solution (1in 5):a brownish-red precipitate is produced.
C: To 100mg add 5mLof sulfuric acid:a green solution is produced,which,on dilution,changes to blue and finally to red.
Absorption characteristics— Dissolve 50mg in 250mLof 50percent alcohol.Dilute 3mLof this solution with 50percent alcohol to 200mL.Determine the absorbance,in a 1-cm cell,with a suitable spectrophotometer.The absorbance maximum is in the range of 530to 533nm;the ratio (P-15)/(P+15)is between 1.10and 1.32,in which Pis the wavelength of maximum absorbance.
[NOTE—Asuitable grade is available as catalog number 10,214-8from Sigma-Aldrich,www.sigma-aldrich.com.]

Salicylaldehyde, 2-HOC6H4CHO—122.12—Clear,colorless to yellowish-green liquid.Specific gravity:about 1.17.Slightly soluble in water;soluble in alcohol and in ether.May contain a stabilizer.
Assay— When examined by gas-liquid chromatography,using suitable apparatus and conditions,it shows a purity of not less than 98%.
Congealing temperature á651ñ: between 1.0and 3.0.
Refractive index á831ñ: between 1.573and 1.574at 20.

Salicylaldazine, C14H12N2O2—240.26—Use a suitable grade or prepare as follows.Dissolve 300mg of hydrazine sulfate in 5mLof water,add 1mLof glacial acetic acid and 2mLof a freshly prepared 1in 5solution of salicylaldehyde in isopropyl alcohol,mix,and allow to stand until a yellow precipitate is formed.Extract the mixture with two 15-mLportions of methylene chloride.Combine the methylene chloride extracts,and dry over anhydrous sodium sulfate.Decant the methylene chloride solution,and evaporate it to dryness.Recrystallize the residue of salicylaldazine from a mixture of warm toluene and methanol (60:40)with cooling.Filter,and dry the crystals in vacuum.
Melting range á741ñ: between 213and 219,but the range between beginning and end of melting does not exceed 1.
Chromatography— Proceed as directed in Limit of hydrazineunder Povidone:the chromatogram shows only one spot.

Sand,Standard 20-to 30-Mesh —Silica sand,composed almost entirely of naturally rounded grains of nearly pure quartz.Predominantly graded to pass an 850-µm (No.20)sieve (85to 100percentage passing)and be retained on a 600-µm (No.30)sieve (0to 5percentage passing).
[NOTE—Asuitable grade is available as Ottawa Standard Sand from Thomas Scientific,99High Hill Road at I-295,P.O.Box 99,Swedesboro,NJ08085-0099.]

Sand,Washed —It may be prepared as follows.Digest clean,hard sand at room temperature with a mixture of 1part of hydrochloric acid and 2parts of water (about 13%of HCl)for several days,or at an elevated temperature for several hours.Collect the sand on a filter,wash with water until the washings are neutral and show only a slight reaction for chloride,and finally dry.Washed sand meets the following tests.
Substances soluble in hydrochloric acid— Digest 10g with a mixture of 10mLof hydrochloric acid and 40mLof water on a steam bath for 4hours,replacing from time to time the water lost by evaporation.Filter,and to 25mLof the filtrate add 5drops of sulfuric acid,evaporate,and ignite to constant weight:the residue weighs not more than 8mg (0.16%).
Chloride(Reagent test)— Shake 1g with 20mLof water for 5minutes,filter,and add to the filtrate 1mLof nitric acid and 1mLof silver nitrate TS:any turbidity produced corresponds to not more than 0.03mg of Cl (0.003%).

Sawdust,Purified —It may be prepared as follows.Extract sawdust in a percolator,first with sodium hydroxide solution (1in 100),and then with dilute hydrochloric acid (1in 100)until the acid percolate gives no test for alkaloid with mercuric-potassium iodide TSor with iodine TS.Then wash with water until free from acid and soluble salts,and dry.Purified sawdust meets the following test.
Alkaloids— To 5g of purified sawdust contained in a flask add 50mLof a mixture of 2volumes of ether and 1volume of chloroform and 10mLof ammonia TS,and shake frequently for 2hours.Decant 20mLof the clear,ether-chloroform liquid,and evaporate to dryness.Dissolve the residue in 2mLof dilute hydrochloric acid (1in 12),and divide into two portions.To 1portion add mercuric-potassium iodide TS,and to the other add iodine TS:no turbidity is produced in either portion.

Scandium Oxide, Sc2O3—137.91[12060-01-1]—Fine,white powder.

Secondary Butyl Alcohol —See Butyl Alcohol,Secondary.

Selenious Acid (Selenous Acid), H2SeO3—128.97—Colorless or white crystals,efflorescent in dry air and hygroscopic in moist air.Soluble in water and in alcohol.
Assay— Accurately weigh about 100mg,transfer to a glass-stoppered flask,and dissolve in 50mLof water.Add 10mLof potassium iodide solution (3in 10)and 5mLof hydrochloric acid,mix,insert the stopper in the flask,and allow to stand for 10minutes.Dilute with 50mLof water,add 3mLof starch TS,and titrate with 0.1Nsodium thiosulfate VSuntil the color is no longer diminished,then titrate with 0.1Niodine VSto a blue color.Subtract the volume of 0.1Niodine solution from the volume of 0.1Nsodium thiosulfate to give the volume of 0.1Nthiosulfate equivalent to selenious acid.Each mLof 0.1Nsodium thiosulfate is equivalent to 3.225mg of H2SeO3:not less than 93%is found.
Insoluble matter— Dissolve 1g in 5mLof water:the solution is clear and complete.
Residue on ignition(Reagent test): not more than 1.0mg (0.01%),from 10g.
Selenate and sulfate— Dissolve 500mg in 10mLof water,and add 0.1mLof hydrochloric acid and 1mLof barium chloride TS:no turbidity or precipitate is formed within 10minutes.

Selenium, Se—At.Wt.78.96—Dark-red amorphous,or bluish-black,crystalline powder.Insoluble in water;soluble in solutions of sodium and potassium hydroxides or sulfides.
Residue on ignition(Reagent test)— One g yields not more than 2mg (0.2%).
Heavy metals— To the Residue on ignitionadd 3mLof hydrochloric acid and 2mLof nitric acid,evaporate on a steam bath to dryness,take up the residue in a mixture of 2mLof diluted hydrochloric acid and 50mLof hot water,cool,filter,and wash the filter with sufficient water to make 100mLof filtrate (Test Solution).To a 30-mLaliquot of the Test Solutionadd 10mLof water and 10mLof hydrogen sulfide TS:the color produced is not darker than that of a Control Solutionprepared from 3mLof Standard Lead Solution(see Heavy Metals á231ñ;0.03mg of Pb),0.2mLof 1Nhydrochloric acid,37mLof water,and 10mLof hydrogen sulfide TS(0.01%).
Iron á241ñ— To 20mLof the Test Solutionprepared in the test for Heavy metalsadd 2mLof hydrochloric acid,and dilute with water to 47mL:the solution shows not more than 0.01mg of Fe (0.005%).
Nitrogen—
STANDARD NITROGEN SOLUTION— Dissolve 382mg of ammonium chloride in water to make 1liter.Each mLof this solution contains the equivalent of 0.1mg of nitrogen (N).
PROCEDURE— Heat 1.0g with 10mLof sulfuric acid in a Kjeldahl flask until the test specimen is dissolved and the volume of acid is reduced to about 5mL.Cool,cautiously dilute with 100mLof water,render strongly alkaline with sodium hydroxide solution (3in 10),and distill about 75mLof the solution into 5mLof water containing 2drops of 1Nhydrochloric acid.Dilute the distillate with water to 250mL.To a 50-mLaliquot of the solution add 1mLof sodium hydroxide solution (1in 10)and 2mLof mercuric-potassium iodide TS:the color produced is not darker than that produced by 0.1mLof Standard nitrogen solution(0.01mg of N)treated in the same manner as the test specimen (0.005%).
Sulfur— To 1.0g in a beaker add,successively,5mLof nitric acid,then 10mLof hydrochloric acid,and evaporate on a steam bath to dryness.Add 10mLof hydrochloric acid,and slowly evaporate again to dryness.Take up the residue in 30mLof dilute hydrochloric acid (1in 30),filter,and wash the filter with water to make about 100mLof the filtrate.Heat the filtrate to boiling,and add slowly,with stirring,5mLof barium chloride TS.Digest on the steam bath for 4hours.Filter on a fine-porosity filter paper,wash the precipitate until it is free from chloride,ignite,and weigh.The weight of the barium sulfate residue,multiplied by 0.1374,represents sulfur (S).Not more than 0.5mg of Sis found (0.05%).

Selenomethionine, C5H11NO2Se—196.11—[Caution—Handle with care,as this reagent is highly toxic. ]
Assay— Weigh accurately about 750mg,dissolve in 100mLof methanol,add crystal violet TS,and titrate with 0.1Nperchloric acid to a blue-green endpoint.Each mLof 0.1Nperchloric acid is equivalent to 19.61mg of C5H11NO2Se:between 97.0%and 103.0%,calculated on the as-is basis,is found.
Melting range á741ñ: about 260,with decomposition.
Nitrogen content á461ñ— Determine by the Kjeldahl method:between 6.8%and 7.4%,calculated on the as-is basis,is found.

Silica,Calcined Diatomaceous —See Diatomaceous Silica,Calcined.

Silica,Chromatographic,Silanized,Flux-Calcined,Acid-washed —Use a suitable grade.
[NOTE—Suitable grades are available commercially as “Aeropak 30,”“Diatoport S,”and “Gas-Chrom Z.”]

Silica Gel —An amorphous,partly hydrated SiO2occurring in glassy granules of varying size.When used as a desiccant,it frequently is coated with a substance that changes color when the capacity to absorb water is exhausted.Such colored products may be regenerated (i.e.,may regain their capacity to absorb water)by being heated at 110until the gel assumes the original color.[NOTE—The following procedures and limits are designed only for use in testing the desiccant grade of silica gel.]
Loss on ignition— Ignite 2g,accurately weighed,at 950±50to constant weight:it loses not more than 6.0%of its weight.
Water absorption— Place about 10g in a tared weighing bottle,and weigh.Then place the bottle,with cover removed,for 24hours in a closed container in which the atmosphere is maintained at 80%relative humidity by being in equilibrium with sulfuric acid having a specific gravity of 1.19.Weigh again:the increase in weight is not less than 31.0%of the weight of test specimen.

Silica Gel,Binder-Free —Silica gel for chromatographic use formulated without a binder,since only activated forms of the silica gel are used as the binding agent.
[NOTE—Asuitable grade is available commercially as “Silica Gel H”.]

Silica Gel,Chromatographic —Use a suitable grade.
[NOTE—Asuitable grade is available commercially as “Silica Gel G”.]

Silica Gel –Impregnated Glass Microfiber Sheet—Use a suitable grade.
[NOTE—Asuitable grade is available commercially as “Seprachrom”Chamber with Type SG ITLC,Product No.51923,from Gelman Instrument Co.,Ann Arbor,MI48106.]

Silica Gel Mixture,Chromatographic —Amixture of silica gel with a suitable fluorescing substance.
[NOTE—Asuitable grade is available commercially as “Silica Gel GF254”.]

Silica Gel Mixture,Chromatographic,with Chemically Bound Amino Groups —Use a suitable grade.

Silica Gel Mixture,Dimethylsilanized,Chromatographic —Use a suitable grade.
[NOTE—Asuitable grade is available as “Silica Gel 60silanized RP-2F254,”from EMD Chemicals,www.emdchemicals.com.]

Silica Gel Mixture,Octadecylsilanized Chromatographic —Use a suitable grade.
[NOTE—Asuitable grade is available commercially as KC-18Ffrom Whatman Chemical Separation,Inc.,9Bridewell Place,Clifton,NJ07014.]

Silica Gel,Octadecylsilanized Chromatographic —Use a suitable grade.
[NOTE—Asuitable grade is available commercially as “Reversed Phase Uniplates”from Analtech,Inc.,Newark,DE19711.]

Silica Gel Mixture,Octylsilanized,Chromatographic —Use a mixture of RP-8chromatographic silica gel with a suitable fluorescing substance agent.

Silica Gel,Porous —Use a grade suitable for high-pressure liquid chromatography.
[NOTE—Asuitable grade for reverse phase high-pressure liquid chromatography is available as “LiChrosorb SI60,Reverse Phase”.]

Silica Microspheres —Use a suitable grade.
[NOTE—Asuitable grade,in a controlled-diameter,spherical,porous form,is available commercially as “Zorbax Sil,”from Agilent,www.agilent.com.]

Siliceous Earth,Chromatographic —
For gas chromatography,use a specially prepared grade meeting the following general description:Purified siliceous earth of suitable mesh size that has been acid-and/or base-washed.It may or may not be silanized.
For column partition chromatography,it is essential that the material be free from interfering substances.If such interferences are known or thought to be present,purify the material as follows:Place a pledget of glass wool in the base of a chromatographic column having a diameter of 100mm or larger,and add Purified Siliceous Earth(NFmonograph)to a height equal to 5times the diameter of the column.Add a volume of hydrochloric acid equivalent to one-third the volume of siliceous earth,and allow the acid to percolate into the column.Wash the column with methanol,using small volumes at first to rinse the walls of the column,and continue washing with methanol until the last washing is neutral to moistened litmus paper.Extrude the washed column into shallow dishes,heat on a steam bath to remove the excess methanol,and dry at 105until the material is powdery and free from traces of methanol.Store the dried material in well-closed containers.
[NOTE—Asuitable grade is “Chromosorb W-AW”.]
[NOTE—Suitable silanized grades for gas chromatography are “Gas Chrom Q,”and “Chromosorb W(AW-DMCS-treated).]
[NOTE—Asuitable grade for column chromatography is acid-washed “Celite 545,”available from Sigma-Aldrich,www.sigma-aldrich.com.]

Siliceous Earth,Chromatographic,Silanized —Place about 450g of purified siliceous earth in a large,open,glass crystallizing dish in a vacuum desiccator containing 30mLof a suitable silane,e.g.,a mixture of 1volume of dimethyldichlorosilane and 1volume of trimethylchlorosilane,or a mixture of 1volume of methyltrichlorosilane and 2volumes of dimethyldichlorosilane.Apply vacuum intermittently for several hours,until no liquid silane remains.Float the treated purified siliceous earth on water,and gently agitate to allow any uncoated particles to sink.Skim the silanized material off the surface,wash it on a sintered-glass funnel with warm methanol until the filtrate no longer is acidic,and dry at 110.

Silicic Acid, SiO2·xH2O—(anhydrous)60.08—White,amorphous powder.Insoluble in water and in acids;soluble in hot solutions of strong alkalies.
Residue on ignition(Reagent test): not less than 80.0%.
Nonvolatile with hydrofluoric acid— Heat 500mg with 1mLof sulfuric acid and 10mLof hydrofluoric acid in a platinum crucible to dryness,and ignite to constant weight:the weight of the residue does not exceed 1.0mg (0.2%).
Chloride(Reagent test)— One g shows not more than 0.05mg of Cl (0.005%).
Sulfate(Reagent test)— Boil 2g with 20mLof dilute hydrochloric acid (1in 40),filter,neutralize the filtrate with ammonia TS,and dilute with water to 20.0mL.A10-mLaliquot of the solution shows not more than 0.1mg of SO4(0.01%).
Heavy metals(Reagent test)— Boil 2.5g with 50mLof dilute hydrochloric acid (1in 10)for 5minutes,filter while hot,and evaporate the filtrate on a steam bath to dryness.Take up the residue in 20mLof dilute hydrochloric acid (1in 500),digest for 5minutes,cool,add water to make 100mL,and filter.To 40mLof the filtrate add 10mLof hydrogen sulfide TS:any color produced is not darker than that produced by adding 10mLof hydrogen sulfide TSto a control containing 0.03mg of Pb (0.003%).
Iron á241ñ— To 20mLof the filtrate obtained in the test for Heavy metalsadd 1mLof hydrochloric acid,and dilute with water to 47mL:the solution shows not more than 0.015mg of Fe (0.003%).

Silicic Acid—Impregnated Glass Microfilament Sheets with Fluorescent Indicator —Use a suitable grade.
[NOTE—One example of a suitable grade is “ITLC Type SAF”sheets,available from Gelman Instrument Co.,600South Wagner Rd.,Ann Arbor,MI48106.]

Silicon Carbide, SiC—40.10—In small clean chips,suitable for use in promoting ebullition.

Silicone (75Percent Phenyl,Methyl) —Use a suitable grade.
[NOTE—Asuitable grade is available as “OV-25”.]

Silicotungstic Acid,n-Hydrate (Tungstosilicic Acid), H4Si(W3O10)4·nH2O—2878.17(anhydrous)—Green powder.
Assay— Dissolve about 1g,accurately weighed,in 25mLof dilute hydrochloric acid (1in 5).Add 50mLof a solution of 5g of cinchonine in dilute hydrochloric acid (1in 2).Warm on a steam bath for about 30minutes.Cool,filter through a tared crucible,and ignite at 800to constant weight.The weight of the residue multiplied by 1.047is equal to the weight of silicotungstic acid dihydrate in the sample taken.Not less than 98%is found.

Silver Diethyldithiocarbamate, (C2H5)2NCS2Ag—256.14—Use ACSreagent grade.

Silver Nitrate, AgNO3—169.87—Use ACSreagent grade.

Silver Oxide, Ag2O—231.74—Brownish-black,heavy odorless powder.Slowly decomposes on exposure to light.Absorbs carbon dioxide when moist.Practically insoluble in water;freely soluble in dilute nitric acid and in ammonia;insoluble in alcohol.Store in well-closed containers;do not expose to ammonia fumes or easily oxidizable substances.
Assay— Dissolve about 500mg,previously dried at 120for 3hours and accurately weighed,in a mixture of 20mLof water and 5mLof nitric acid.Dilute with 100mLof water,add 2mLof ferric ammonium sulfate TS,and titrate with 0.1Nammonium thiocyanate VSto a permanent reddish-brown color.Each mLof 0.1Nammonium thiocyanate is equivalent to 11.59mg of Ag2O:not less than 99.7%of Ag2Ois found.
Loss on drying— Dry it at 120for 3hours:it loses not more than 0.25%of its weight.
Nitrate— To 500mg add 30mg of sodium carbonate and 2mLof phenoldisulfonic acid TS,mix,and heat on a steam bath for 15minutes.Cool,cautiouslyadd 20mLof water,render alkaline with ammonia TS,and dilute with water to 30mL:any color produced by the test solution is not darker than that produced in a control containing 0.01mg of NO3(0.002%).
Substances insoluble in nitric acid— Dissolve 5g in a mixture of 5mLof nitric acid and 10mLof water,dilute with water to about 65mL,and filter any undissolved residue on a tared filtering crucible (retain the filtrate for the test for Substances not precipitated by hydrochloric acid).Wash the crucible with water until the last washing shows no opalescence with 1drop of hydrochloric acid,and dry at 105to constant weight:the residue weighs not more than 1mg (0.02%).
Substances not precipitated by hydrochloric acid— Dilute the filtrate obtained in the test for Substances insoluble in nitric acidwith water to 250mL,heat to boiling,and add,dropwise,sufficient hydrochloric acid to precipitate all of the silver (about 5mL),avoiding any great excess.Cool,dilute with water to 300mL,and allow to stand overnight.Filter,evaporate 200mLof the filtrate in a suitable tared porcelain dish to dryness,and ignite:the residue weighs not more than 1.7mg (0.05%).
Alkalinity— Heat 2g with 40mLof water on a steam bath for 15minutes,cool,and dilute with water to 50mL.Filter,discarding the first 10mLof the filtrate.To 25mLof the subsequent filtrate add 2drops of phenolphthalein TS,and titrate with 0.02Nhydrochloric acid VSto the disappearance of any pink color:not more than 0.20mLis required (0.016%as NaOH).

b-Sitosterol, (22:23Dihydrostigmasterol), C29H50O—414.7[83-46-5]—White powder.Soluble in chloroform.Store in a freezer.
Specific rotation á781Sñ: between –33and –39,determined in a solution containing 0.5g of test specimen per mLof chloroform.
Water,Method Iá921ñ: not more than 6%.

Soda Lime —Use Soda Lime(NFmonograph).

Sodium, Na—At.Wt.22.98977—Use ACSreagent grade.

Sodium Acetate, NaC2H3O2·3H2O—136.08—Use ACSreagent grade Sodium Acetate Trihydrate.

Sodium Acetate,Anhydrous, NaC2H3O2—82.03—Use ACSreagent grade.

Sodium Alizarinsulfonate (Alizarin Red S;Alizarin Sodium Monosulfonate), C14H7NaO7S·H2O—360.27—Yellow-brown or orange-yellow powder.Freely soluble in water,with production of a yellow color;sparingly soluble in alcohol.
Sensitiveness— Add 3drops of a solution of it (1in 100)to 100mLof water,and add 0.25mLof 0.02Nsodium hydroxide:a red color is produced.Add 0.25mLof 0.02Nhydrochloric acid:the original yellow color returns.

Sodium Ammonium Phosphate (Microcosmic Salt), NaNH4HPO4·4H2O—209.07—Colorless crystals or white granules.Freely soluble in water;insoluble in alcohol.Effloresces in air and loses ammonia.
Insoluble matterand ammonium hydroxide precipitate— Dissolve 10g in 100mLof water,add 10mLof ammonia TS,and heat on a steam bath for 1hour.If any precipitate is formed,filter,wash well with water,and ignite:the ignited precipitate weighs not more than 1mg (0.01%).
Chloride(Reagent test)— One g shows not more than 0.02mg of Cl (0.002%).
Heavy metals— Dissolve 3g in 25mLof water,add 15mLof 1Nsulfuric acid,then add 10mLof hydrogen sulfide TS:any brown color developed in 1minute is not darker than that of a control containing 3mLof Standard Lead Solution(see á231ñ)and 0.5mLof 1Nsulfuric acid (0.001%).
Nitrate— Dissolve 1g in 10mLof water,add 0.1mLof indigo carmine TS,then add,with stirring,10mLof sulfuric acid:the blue color persists for 10minutes (about 0.005%).
Sulfate(Reagent test,Method II)— Dissolve 10g in 100mLof water,add 5mLof hydrochloric acid,and filter if necessary:the filtrate yields not more than 5mg of residue (0.02%).

Sodium Arsenate (Arsenic Acid Sodium Salt), Na2HAsO4·7H2O—312.01[10048-95-0]—Use ACSreagent grade.

Sodium Arsenite, NaAsO2—129.91—White,crystalline,odorless powder.Soluble in water;slightly soluble in alcohol.
Assay— Transfer about 5.5g,accurately weighed,to a 500-mLvolumetric flask,dissolve in water,dilute with water to volume,and mix.Pipet 25mLof this solution into a suitable container,add 50mLof water and 5g of dibasic sodium phosphate,swirl to dissolve,and titrate with 0.1Niodine VS,adding 3mLof starch TSas the endpoint is approached.Each mLof 0.1Niodine is equivalent to 3.746mg of As.Between 57.0%and 60.5%is found (equivalent to 98.8%to 104.9%of NaAsO2).
Chloride(Reagent test)— One g shows not more than 0.10mg of Cl (0.01%).
Heavy metals— Dissolve 200mg in 8mLof dilute hydrochloric acid (3in 8),and evaporate on a steam bath to dryness.Dissolve the residue in 5mLof dilute hydrochloric acid (2in 5),and again evaporate to dryness.Dissolve the residue in 10mLof water,and add 2mLof diluted acetic acid and 10mLof hydrogen sulfide TS.Any brown color produced is not darker than that of a control containing 0.01mg of added Pb (0.005%).
Iron— Dissolve 1g in 20mLof dilute hydrochloric acid (1in 5),and add,dropwise,a slight excess of bromine TS.Boil the solution to remove the excess bromine,cool,dilute with water to 40mL,and add 10mLof ammonium thiocyanate solution (3in 10).Any red color produced is not darker than that of a control containing 0.02mg of added Fe (0.02%).
Sulfide— Dissolve 1g in 20mLof water,and add 5drops of lead acetate TS:no brown color is produced (about 0.0005%).
Sulfate(Reagent test,Method II)— Dissolve 5g in 100mLof water,add methyl orange TS,neutralize with 1Nhydrochloric acid,add 3mLof the acid in excess,and filter:the filtrate yields not more than 3mg of residue (0.02%).

Sodium Azide, NaN3—65.01—White powder.
Assay— [Caution—Sodium azide is a potent poison.Its conjugate acid HN3is more toxic than hydrogen cyanide and is readily liberated from neutral aqueous solutions.Contact of NaH3or hydrazoic (HN3)with certain metals may produce explosive salts.Work in a well-ventilated hood,and handle the sample with care. ]Dissolve about 100mg,accurately weighed,in 50mLof water,and add 3drops of phenolphthalein.Adjust the pH,if necessary,to 7.0,and add 35.0mLof 0.1Nperchloric acid.Pipet,while stirring,2.5mLof 1.0Msodium nitrite into the solution,and stir for 15seconds.Titrate rapidly to the phenolphthalein endpoint with 0.1Nsodium hydroxide.The endpoint should be reached in less than 4minutes after addition of perchloric acid because HN3is readily volatile.Calculate the percentage of azide by the formula:
[(Np)(Vp)-(Ns)(Vs)](65.01)(100)/2C,
where Npis the normality of perchloric acid solution;Vpis the volume of perchloric acid,in mL,taken;Nsis the normality of sodium hydroxide solution;Vsis the volume,in mL,of sodium hydroxide taken;65.01is the molecular weight of sodium azide;and Cis the weight,in mg,of sodium azide.Not less than 98.5%of NaN3is found.

Sodium Bicarbonate, NaHCO3—84.01—Use ACSreagent grade.

Sodium Biphenyl, C12H9Na—176.19—Supplied as a solution (10percent to 30percent,w/w)in a mixture of dimethoxyethane and toluene or xylene.The solution is a viscous,dark green liquid.[NOTE—The solution deteriorates at a rate of about 10%per month.Use only freshly prepared solution.]
Activity— Place 20mLof dry toluene in a titration flask equipped with a magnetic stirring bar and a stopper having a hole through which the delivery tip of a weight buret may be inserted.Add a quantity of sodium biphenyl sufficient to produce a blue color in the mixture,and titrate with amyl alcohol,contained in a weight buret,to the disappearance of the blue color.(Disregard the amounts of sodium biphenyl and amyl alcohol used in this adjustment.)Weigh accurately the weight buret containing the amyl alcohol.Transfer the contents of a vial of well-mixed test specimen to the titration flask,and titrate quickly with the amyl alcohol to the disappearance of the blue color.Weigh the buret to determine the weight of amyl alcohol consumed,and calculate the activity,in mEq per vial,by the formula:
11.25W,
in which Wis the weight of amyl alcohol consumed.Not less than 10%activity is found.
Iodine content— Add 10mLto 5mLof toluene contained in a 125-mLseparator fitted with a suitable inert plastic stopcock,and shake vigorously for 2minutes.Extract gently with three 10-mLportions of dilute phosphoric acid (1in 3),combining the lower phases in a 125-mLiodine flask.Add sodium hypochlorite TS,dropwise,to the combined extracts until the solution turns brown,then add 0.5mLin excess.Shake intermittently for 3minutes,add 5mLof freshly prepared,saturated phenol solution,mix,and allow to stand for 1minute,accurately timed.Add 1g of potassium iodide,shake for 30seconds,add 3mLof starch TS,and titrate with 0.1Nsodium thiosulfate VS:not more than 0.1mLof 0.1Nsodium thiosulfate is consumed.

Sodium Biphosphate, NaH2PO4·H2O—137.99—Use ACSreagent grade Sodium Phosphate,Monobasic.

Sodium Bisulfite —Use ACSreagent grade Sodium Metabisulfite.

Sodium Bitartrate, NaHC4H4O6·H2O—190.08—White crystals or a crystalline powder.Soluble in cold water.
Assay— Dissolve about 500mg,accurately weighed,in 30mLof water,add phenolphthalein TS,and titrate with 0.1Nsodium hydroxide VS:each mLof 0.1Nsodium hydroxide is equivalent to 19.01mg of NaHC4H4O6·H2O.Between 99%and 100.5%is found.
Insoluble matter(Reagent test): not more than 1mg,from 10g (0.01%).
Chloride(Reagent test)— One g shows not more than 0.2mg of Cl (0.02%).
Heavy metals(Reagent test)— Dissolve 4g in 25mLof water,add 2drops of phenolphthalein TS,and then add ammonia TS,dropwise,until the solution is slightly pink.Add 4mLof 1Nhydrochloric acid,dilute with water to 40mL,and add 10mLof hydrogen sulfide TS:any brown color produced is not darker than that of a control containing 0.04mg of added Pb (0.001%).
Sulfate(Reagent test,Method I)— One g shows not more than 0.2mg of SO4(0.02%).

Sodium Borate (Borax;Sodium Tetraborate), Na2B4O7·10H2O—381.37—Use ACSreagent grade.
[NOTE—Certified Borax is available from the National Institute of Standards and Technology,Washington,DC,www.nist.gov,as standard sample No.187.]

Sodium Borohydride, NaBH4—37.83—White,crystalline solid.Freely soluble in water;soluble (with reaction)in methanol.Its solutions are rapidly decomposed by boiling.
Assay—
POTASSIUM IODATE SOLUTION(0.25N)— Dissolve 8.917g,previously dried at 110to constant weight and accurately weighed,in water to make 1000.0mL.
PROCEDURE— Dissolve about 500mg,accurately weighed,in 125mLof sodium hydroxide solution (1in 25)in a 250-mLvolumetric flask,dilute with the sodium hydroxide solution to volume,and mix.Pipet 10mLof the solution into a 250-mLiodine flask,add 35.0mLof Potassium iodate solution,and mix.Add 2g of potassium iodide,mix,add 10mLof dilute sulfuric acid (1in 10),insert the stopper in the flask,and allow to stand in the dark for 3minutes.Titrate the solution with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Calculate the amount,in mg,of NaBH4in the specimen titrated by the formula:
([(35.0)(0.25)]-0.1V)4.729,
in which Vis the volume,in mL,of 0.1Nsodium thiosulfate used in the titration.Not less than 98%is found.

Sodium Bromide, NaBr—102.89—Use ACSreagent grade.

Sodium Carbonate —Use Sodium Carbonate,Anhydrous.

Sodium Carbonate,Anhydrous, Na2CO3—105.99—Use ACSreagent grade.

Sodium Chloride, NaCl—58.44—Use ACSreagent grade.

Sodium Chloride Solution,Isotonic —Use Saline TS.

Sodium Chromate, Na2CrO4·4H2O—234.03—Lemon-yellow,odorless crystals.Soluble in water.
Assay— Accurately weigh about 300mg,and dissolve in 10mLof water contained in a 500-mLflask.Add 3g of potassium iodide and 10mLof diluted sulfuric acid,and dilute with 350mLof oxygen-free and carbon dioxide-free water.Titrate the liberated iodine with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Each mLof 0.1Nsodium thiosulfate consumed is equivalent to 7.802mg of Na2CrO4·4H2O.Not less than 99%is found.
Insoluble matter(Reagent test): not more than 1mg,from 20g dissolved in 150mLof water (0.005%).
Aluminum— Dissolve 20g in 140mLof water,filter,and add 5mLof glacial acetic acid to the filtrate.Add stronger ammonia water until alkaline,and digest for 2hours on a steam bath.Filter through hardened filter paper,wash thoroughly,ignite,and weigh:the residue weighs not more than 0.8mg (0.002%).
Calcium— Determine as directed in the test for calcium for ACSreagent grade Potassium Chromate (0.005%).
Chloride— Determine as directed in the test for chloride for ACSreagent grade Potassium Chromate (about 0.005%).
Sulfate— Determine as directed in the test for sulfate for ACSreagent grade Potassium Dichromate,but add 4.5mLof hydrochloric acid to the water used to dissolve the test specimen:the residue weighs not more than 2.4mg (0.01%).

Sodium Chromotropate —See Chromotropic Acid.

Sodium Cobaltinitrite, Na3Co(NO2)6—403.94—Use ACSreagent grade.

Sodium Cyanide, NaCN—49.01—Use ACSreagent grade.

Sodium Desoxycholate —Use Bile Salts.

Sodium Dichromate, Na2Cr2O7·2H2O(for chromic acid cleaning mixture)—298.00—Use ACSreagent grade.

Sodium Diethyldithiocarbamate, (C2H5)2NCS2Na·3H2O—225.31—Use ACSreagent grade.

Sodium 2,2-dimethyl-2-silapentane-5-sulfonate —See Sodium 3-(trimethylsilyl)-1-propane sulfonate.

Sodium Dithionite —Use Sodium Hydrosulfite.

Sodium Dodecyl Sulfate(Sodium Lauryl Sulfate), C12H25SO4Na—288.38—Light yellow,crystalline powder.

Sodium Ferrocyanide, Na4Fe(CN)6·10H2O—484.06—Yellow crystals or granules.Freely soluble in water.
Assay— Dissolve 2g,accurately weighed,in 400mLof water,add 10mLof sulfuric acid,and titrate with 0.1Npotassium permanganate VS.Each mLof 0.1Npotassium permanganate is equivalent to 48.41mg of Na4Fe(CN)6·10H2O.Not less than 98%is found.
Insoluble matter(Reagent test): not more than 1mg,from 10g (0.01%).
Chloride(Reagent test)— Dissolve 1g in 75mLof water,add a solution prepared by dissolving 1.2g of cupric sulfate in 25mLof water,mix,and allow to stand for 15minutes.To 20mLof the decanted,clear liquid add 2mLof nitric acid and 1mLof silver nitrate TS:any turbidity produced does not exceed that of a control containing 0.02mg of Cl,2mLof nitric acid,1mLof silver nitrate TS,and sufficient cupric sulfate to match the color of the test solution.
Sulfate— Dissolve 5g in 100mLof water without heating,filter,and to the filtrate add 0.25mLof glacial acetic acid and 5mLof barium chloride TS:no turbidity is produced in 10minutes (about 0.01%as SO4).

Sodium Fluorescein —C20H10Na2O5—376.28—Orange-red,hygroscopic powder.Freely soluble in water;slightly soluble in alcohol.Its water solution is yellowish red in color and exhibits a strong yellowish green fluorescence that disappears when the solution is acidified and reappears when the solution is neutralized or made basic.
Loss on drying á731ñ— Dry it at 120to constant weight:it loses not more than 7.0%of its weight.

Sodium Fluoride, NaF—41.99—Use ACSreagent grade.

Sodium Glycocholate, C26H42NNaO6—487.60—White to tan,odorless or practically odorless powder.Is hygroscopic.Freely soluble in water and in alcohol.
Specific rotation á781ñ: between +28and +31,calculated on the dried basis (it is rendered anhydrous by drying at 100for 2hours),determined at 20in a solution containing 10mg per mL.
Nitrogen,Method Iá461ñ— Between 2.6%and 3.2%of Nis found,calculated on the dried basis.

Sodium 1-Decanesulfonate— Use a suitable grade.

Sodium 1-Heptanesulfonate, C7H15NaO3S—202.25—Use a suitable grade.
Add the following:

Sodium 1-Heptanesulfonate Monohydrate, C7H15NaO3S·H2O—220.26[22767-50-6]—Use a suitable grade.USP28

Sodium 1-Hexanesulfonate, C6H13NaO3S—188.22—Use a suitable grade.

Sodium Hydrosulfite (Sodium Dithionite), Na2S2O4—174.11—White or grayish-white crystalline powder.Soluble in water;slightly soluble in alcohol.Gradually oxidizes in air,more readily when in solution,to bisulfite,acquiring an acid reaction.Is affected by light.
Assay— Accurately weigh about 1g,dissolve it in a mixture of 10mLof formaldehyde TSand 10mLof water contained in a small glass-stoppered flask,and allow to stand for 30minutes with frequent agitation.Transfer the solution to a 250-mLvolumetric flask,add 150mLof water and 3drops of methyl orange TS,and then add,dropwise,1Nsulfuric acid to a slightly acid reaction.Dilute with water to 250mL,and mix.To 50.0mLof the dilution add 2drops of phenolphthalein TSand just sufficient 0.1Nsodium hydroxide to produce a slight,pink color,then titrate with 0.1Niodine,adding 3mLof starch TSas the indicator.Then discharge the blue color of the solution with 1drop of 0.1Nsodium thiosulfate,and titrate with 0.1Nsodium hydroxide VSto a pink color:each mLof 0.1Nsodium hydroxide is equivalent to 3.482mg of Na2S2O4.Not less than 88%is found.
Sulfide— Add sodium hydroxide solution (1in 10)to lead acetate TSuntil the precipitate dissolves.Add 5drops of this solution to a solution of 1g of the sodium hydrosulfite in 10mLof water:no immediate darkening is observed.
Heavy metals— Dissolve 1g in 10mLof water,add 10mLof hydrochloric acid,and evaporate on a steam bath to dryness.Dissolve the residue in 20mLof water and 0.5mLof diluted hydrochloric acid,filter,and add to the filtrate 10mLof hydrogen sulfide TS:no darkening is produced.Render the solution alkaline with ammonia TS:a slight,greenish color may be produced,but not a dark or white precipitate.
Suitability for riboflavin assay— To each of 2or more tubes add 10mLof water and 1.0mLof a standard riboflavin solution containing 20µg of riboflavin in each mL,and mix.To each tube add 1.0mLof glacial acetic acid,mix,add with mixing,0.5mLof potassium permanganate solution (1in 25),and allow to stand for 2minutes.Then to each tube add,with mixing,0.5mLof hydrogen peroxide TS:the permanganate color is destroyed within 10seconds.Shake the tubes vigorously until excess oxygen is expelled.If gas bubbles remain on the sides of tubes after foaming has ceased,remove the bubbles by tipping the tubes so that the solution flows slowly from end to end.In a suitable fluorometer,measure the fluorescence of the solution.Then add,with mixing,8.0mg of sodium hydrosulfite:the riboflavin is completely reduced in not more than 5seconds.

Sodium Hydroxide, NaOH—40.00—Use ACSreagent grade.

Sodium Hypochlorite Solution —Asolution of sodium hypochlorite (NaOCl)in water.Usually yellow to yellowish-green in color.Has an odor of chlorine.Is affected by light and gradually deteriorates.Store it in light-resistant containers,preferably below 25.[Caution—This solution is corrosive and may evolve gases that are corrosive and toxic.It is a powerful oxidant that can react violently with reducing agents.Is irritating and corrosive to skin and mucous membranes. ]
Assay— Transfer about 3mLto a tared,glass-stoppered iodine flask,and weigh accurately.Add 50mLof water,2g of potassium iodide,and 10mLof acetic acid,insert the stopper in the flask,and allow to stand in the dark for 10minutes.Remove the stopper,rinse the walls of the flask with a few mLof water,and titrate the liberated iodine with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is neared.Each mLof 0.1Nsodium thiosulfate consumed is equivalent to 3.723mg of NaOCl:not less than 5.25%is found.If it is desired to calculate the percentage of available chlorine,note that each mLof 0.1Nsodium thiosulfate consumed is equivalent to 3.545mg of available chlorine.
Calcium— Transfer 10.0g to a 150-mLbeaker,dissolve in 10mLof water,and add 5mLof hydrochloric acid and 2g of potassium iodide.Heat the mixture for 5minutes,cool,and add 2mLof 30percent hydrogen peroxide.Evaporate to dryness,cool,and add 2mLof hydrochloric acid and 2mLof 30percent hydrogen peroxide.Rinse the inner walls of the beaker with a few mLof water,and evaporate to dryness.Take up the residue in 20mLof water,and filter if necessary.To the filtrate add ammonium hydroxide until the solution is just alkaline,then add 4drops of ammonium hydroxide and 5mLof ammonium oxalate TS:any turbidity produced within 15minutes does not exceed that in a blank containing 0.1mg of added Ca carried through the entire procedure (0.001%).
Phosphate(Reagent test)— Transfer 2g to a beaker,and add 5mLof hydrochloric acid and 2g of potassium iodide.Heat the solution for 5minutes,and cool.Add 2mLof 30percent hydrogen peroxide,and evaporate the solution to dryness.Rinse the walls of the beaker with a few mLof water,and add 2mLof hydrochloric acid and 2mLof 30percent hydrogen peroxide.Evaporate again to dryness:the residue shows not more than 0.01mg of PO4(5ppm).

Sodium Lauryl Sulfate— SeeSodium Dodecyl Sulfate.

Sodium Metabisulfite, Na2S2O5—190.11—Use ACSreagent grade.

Sodium Metaperiodate, NaIO4—213.89—Use ACSreagent grade Sodium Periodate.

Sodium Methoxide, CH3ONa—54.02—Fine,white powder.Reacts violently with water with evolution of heat.Soluble in alcohol and in methanol.
Assay— Transfer about 220mg to a tared,glass-stoppered flask,and weigh accurately.Dissolve the test specimen in about 10mLof methanol,then add 100mLof water slowly,with stirring.Add phenolphthalein TS,and titrate with 0.1Nhydrochloric acid VSto a colorless endpoint:each mLof 0.1Nhydrochloric acid VSis equivalent to 5.402mg of CH3ONa.Not less than 98.0%is found.

Sodium Molybdate, Na2MoO4·2H2O—241.95—Use ACSreagent grade.

Sodium Nitrate, NaNO3—84.99—Use ACSreagent grade.

Sodium Nitrite, NaNO2—69.00—Use ACSreagent grade.

Sodium Nitroferricyanide (Sodium Nitroprusside), Na2Fe (NO)(CN)5·2H2O—297.95—Use ACSreagent grade.

Sodium 1-Octanesulfonate, C8H17NaO3S—216.27—Use a suitable grade.

Sodium Oxalate, Na2C2O4—134.00—Use ACSreagent grade.
[NOTE—Sodium Oxalate of a quality suitable as a primary standard is available from the Office of Standard Reference Materials,National Institute of Standards and Technology,Washington,DC,www.nist.gov,as standard sample No.40.]

Sodium (tri)Pentacyanoamino Ferrate [Trisodium Aminepentacyanoferrate (3-)], Na3[Fe(CN)5NH3]—271.93—Yellow to tan powder.Soluble in water.
Solubility— Dissolve 500mg in 50mLof water,and allow to stand for 1hour:the solution is clear and free from foreign matter.
Sensitivity—
1,1-DIMETHYLHYDRAZINE STANDARD SOLUTION—Place 500mLof water in a 1-liter volumetric flask,and add from a buret 1.27mLof anhydrous 1,1-dimethylhydrazine.Dilute with water to volume,and mix.Pipet 10mLof this solution into a 100-mLvolumetric flask,and dilute with water to volume.Each mLof this solution contains the equivalent of 100µg of 1,1-dimethylhydrazine.
BUFFER SOLUTION— Transfer 4.8g of citric acid monohydrate to a 1-liter volumetric flask,dissolve in water,add 14.6g of sodium phosphate,swirl to dissolve,and dilute with water to volume.
TEST PREPARATION— Dissolve 100mg of sodium (tri)pentacyanoamino ferrate in 100mLof water.
PROCEDURE— Into each of five 25-mLvolumetric flasks pipet 0,0.25,0.50,1.0,and 1.5mL,respectively,of 1,1-Dimethylhydrazine standard solution,to each add 15mLof Buffer solution,and swirl to mix.To each flask,add by pipet 2mLof Test preparation,mix,dilute with Buffer solutionto volume,and allow to stand for 1hour.Using a suitable spectrophotometer,1-cm cells,and the solution containing no 1,1-Dimethylhydrazine standard solutionas the blank,determine the absorbances of the remaining solutions at 500nm.Plot the observed absorbance as the ordinate versus the concentration of standard as the abscissa on coordinate paper,and draw the curve of best fit.The plot is linear and the absorbance of the 150-µg solution is not less than 0.65.

Sodium 1-Pentanesulfonate, C5H11NaO3S·H2O—192.21—White,crystalline solid.Soluble in water.
Solubility— One g,dissolved in 25mLof water,yields a clear and complete solution.
Water,Method Iá921ñ: not more than 2.0%.

Sodium Perchlorate, NaClO4·H2O—140.46—Use ACSreagent grade.

Sodium Peroxide, Na2O2—77.98—Use ACSreagent grade.

Sodium Phosphate,Dibasic (Disodium Phosphate;Disodium Hydrogen Phosphate;Sodium Phosphate,Dibasic,Heptahydrate), Na2HPO4·7H2O—268.07—Use ACSreagent grade Sodium Phosphate,Dibasic,Heptahydrate.

Sodium Phosphate,Dibasic,Anhydrous (Anhydrous Disodium Hydrogen Phosphate)(for buffer solutions), Na2HPO4—141.96—Use ACSreagent grade Sodium Phosphate,Dibasic,Anhydrous.

Sodium Phosphate,Monobasic, NaH2PO4·H2O—137.99—Use ACSreagent grade.

Sodium Phosphate,Tribasic, Na3PO4·12H2O—380.12—Use ACSreagent grade.

Sodium Pyrophosphate, Na4P2O7·10H2O—265.90—Use ACSreagent grade.

Sodium Pyruvate, CH3COCO2Na—110.04—White to practically white powder or crystalline solid.Soluble in water.
Assay— Transfer about 300mg,accurately weighed,to a high-form titration beaker,add 150mLof glacial acetic acid,and stir until dissolved.Titrate with 0.1Nperchloric acid VS,determining the endpoint potentiometrically,using a glass electrode and a calomel electrode modified to use 0.1Ntetramethylammonium chloride in methanol as the electrolyte.Perform a blank determination,and make any necessary correction.Each mLof 0.1Nperchloric acid is equivalent to 11.00mg of CH3COCO2Na:not less than 98.0%is found.
Solubility— Dissolve 1.5g in 25mLof water:the solution is clear and complete.
Free acid— Dissolve 10g in 150mLof water,and titrate with 0.5Nsodium hydroxide VS,determining the endpoint potentiometrically:not more than 2.8mLof 0.5Nsodium hydroxide is consumed (about 1%as C3H4O3).

Sodium Salicylate —It complies with the specifications under Sodium Salicylate (USPmonograph),and in addition meets the requirements of the following test.
Nitrate— Dissolve 100mg in 5mLof water,and superimpose the solution upon 5mLof sulfuric acid:no brownish-red color appears at the junction of the two liquids.

Sodium Selenite, Na2SeO3—172.94—White,odorless,crystalline powder,usually partially hydrated.Freely soluble in water;insoluble in alcohol.
Assay— Accurately weigh about 180mg,previously dried at 120to constant weight,and dissolve it in 50mLof water in a glass-stoppered flask.Add,successively,3g of potassium iodide and then 5mLof hydrochloric acid,insert the stopper,and allow to stand for 10minutes.Add 50mLof water,50.0mLof 0.1Nsodium thiosulfate VS,and 3mLof starch TS,and immediately titrate with 0.1Niodine VSto a blue color.Perform a blank determination.The difference in volumes of 0.1Niodine is equivalent to 4.323mg of Na2SeO3.Between 98%and 101%is found.
Solubility— One g in 10mLof water shows not more than a faint haze.
Carbonate— To 500mg add 1mLof water and 2mLof diluted hydrochloric acid:no effervescence is produced.
Chloride(Reagent test)— A500-mg portion shows not more than 0.05mg of Cl (0.01%).
Nitrate(Reagent test)— A200-mg portion dissolved in 3mLof water shows not more than 0.02mg of NO3(0.01%).
Selenateand sulfate (as SO4)— To 500mg in a small evaporating dish add 20mg of sodium carbonate and 10mLof hydrochloric acid.Slowly evaporate the solution on a steam bath under a hood to dryness.Wash the sides of the dish with 5mLof hydrochloric acid,and again evaporate to dryness.Dissolve the residue in a mixture of 15mLof hot water and 1mLof hydrochloric acid.Proceed as directed under Sulfate in Reagents(Reagent test,Method I),beginning with “Filter the solution.”The test specimen shows no more turbidity than that produced by 0.15mg of SO4(0.03%).

Sodium Sulfate (Glauber's Salt), Na2SO4·10H2O—322.20—Use ACSreagent grade.

Sodium Sulfate,Anhydrous, Na2SO4—142.04—Use ACSreagent grade.
For use in assaying alkaloids by gas-liquid chromatography,it conforms also to the following additional test.
Suitability for alkaloid assays— Transfer about 10mg of atropine,accurately weighed,to a 25-mLvolumetric flask,dissolve in alcohol,and dilute with alcohol to volume.Pipet 3mLof the solution into each of two 60-mLseparators,and add to each 10mLof water,1mLof 1Nsodium hydroxide,and 10mLof chloroform.Shake thoroughly,and allow the layers to separate.Filter the organic phase from one separator through phase-separating paper,previously washed with 5mLof chloroform,supported in a funnel,and collect the filtrate in a suitable container.Add 10mLof chloroform to the separator,shake thoroughly,and filter the organic layer through the same phase-separating paper,collecting and combining the filtrates in the same container.Designate the combined filtrates as Solution A.Filter the organic phase from the second separator through 30g of the Anhydrous Sodium Sulfate,supported on a pledget of glass wool in a small funnel,and previously washed with chloroform,and collect the filtrate in a suitable container.Add 10mLof chloroform to the separator,shake thoroughly,and filter the organic layer through the same portion of anhydrous sodium sulfate,collecting and combining the two filtrates in the same container.Designate the combined filtrates as Solution B.Evaporate the two solutions in vacuum to a volume of about 1mL.Inject an accurately measured volume of Solution Ainto a suitable gas chromatography,and record the peak height.Repeat the determination with a second accurately measured volume of Solution A,record the peak height,and obtain the average of the two results.In a similar manner,determine the peak height of two portions of Solution B,and obtain the average of the results.The average value obtained for Solution Bis within 5.0%of the value obtained for Solution A.
Under typical conditions,the gas chromatograph contains a 4-mm ×1.2-m glass column packed with 3%phase G3on packing S1A.After curing and conditioning,the column is maintained at 210,the injector port at 225,and the detector block at 240during the determinations.The carrier gas is helium,flowing at a rate of 60mLper minute.

Sodium Sulfate Decahydrate —Use Sodium Sulfate.

Sodium Tetraphenylborate, NaB(C6H5)4—342.22—Use ACSreagent grade.

Sodium Sulfide, Na2S·9H2O—240.18—Use ACSreagent grade.

Sodium Sulfite —Use Sodium Sulfite,Anhydrous.

Sodium Sulfite,Anhydrous (Exsiccated Sodium Sulfite), Na2SO3—126.04—Use ACSreagent grade.

Sodium p-Sulfophenylazochromotropate [Trisodium Salt of 4,5-Dihydroxy-3-(p-sulfophenylazo)-2,7-naphthalenedisulfonic Acid], C16H9N2Na3O11S3·3H2O—624.47—Bright red powder.Very soluble in water;insoluble in alcohol.Combines with zirconium oxychloride to form a soluble pink zirconium lake.
[NOTE—The reagent is available as Catalog No.7309from Distillation Products Industries,Eastman Organic Chemicals Dept.,Rochester,NY14650.Aprocedure for its preparation is described in Z.Anal.Chem.,146,417(1955).]

Sodium Tartrate, Na2C4H4O6·2H2O—230.08—Use ACSreagent grade.

Sodium Tetraphenylborate, NaB(C6H5)4—342.22—Use ACSreagent grade.

Sodium Tetraphenylboron —See Sodium Tetraphenylborate.

Sodium Thioglycolate (Sodium Thioglycollate), HSCH2COONa—114.10—Awhite,crystalline powder,having a slight,characteristic odor.Very soluble in water;slightly soluble in alcohol.Is hygroscopic,and oxidizes in air.Store in tight,light-resistant containers.It should not be used if it is pale yellow or darker in color.
Assay— Accurately weigh about 250mg,and dissolve in 50mLof oxygen-free water.Add 5mLof diluted hydrochloric acid,boil for 2minutes,cool,and titrate the solution with 0.1Niodine VS,adding 3mLof starch TStoward the end:each mLof 0.1Niodine is equivalent to 11.41mg of HSCH2COONa.Not less than 75%is found.
Insoluble matter— Asolution of 1g in 10mLof water is clear,and practically complete.
Sulfide— Dissolve 500mg in 10mLof water in a small flask,add 2mLof hydrochloric acid,then place a strip of filter paper,moistened with lead acetate TS,over the mouth of the flask,and bring the solution to a boil:the lead acetate paper is not darkened.

Sodium Thiosulfate, Na2S2O3·5H2O—248.19—Use ACSreagent grade.

Sodium L-Thyroxine —Use Levothyroxine Sodium(USPmonograph).

Sodium 3-(trimethylsilyl)-1-propane sulfonate (Sodium 2,2-dimethyl-2-silapentane-5-sulfonate), C6H15SiNaO3S—218.32—Use a suitable grade.

Sodium Tungstate, Na2WO4·2H2O—329.85—Use ACSreagent grade.

Soluble Starch —See Starch,Soluble.

Solvent Hexane —See Hexane,Solvent.

Standard Sand,20-to 30-Mesh —See Sand,Standard 20-to 30-mesh.

Stannous Chloride, SnCl2·2H2O—225.65—Use ACSreagent grade.

Starch,Potato —The starch separated from the tubers of Solanum tuberosumLinné(Fam.Solanaceae).Amore or less finely granular powder,consisting of starch grains of characteristic shape and appearance when examined microscopically.

Starch,Soluble (for iodimetry)—Use ACSreagent grade.

Starch,Soluble,Purified— White,amorphous powder;under microscopic examination it shows the characteristic form of potato starch.Soluble in hot water;very slightly soluble in alcohol.
TEST SOLUTION FOR DETERMINATION OF PH AND SENSITIVITY— Stir 2.0g in 10mLof water,add boiling water to make 100mL,and boil for 2minutes.The hot solution is almost clear.On cooling,the solution may become opalescent or turbid,but does not gel.Use it as the Test solution.
pHá791ñ— The pHof the Test solutionis between 6.0and 7.5.
Sensitivity— Mix 2.5mLof Test solution,97.5mLof water,and 0.50mLof 0.010Niodine:a distinct blue color results,and it disappears upon the addition of 0.50mLof 0.010Nsodium thiosulfate.
Absorbance— Prepare a pH5.3buffer solution by dissolving 43.5g of sodium acetate (trihydrate)and 4.5mLof glacial acetic acid in water,transferring the resultant solution to a 250-mLvolumetric flask,adding water to volume,and mixing.
Dissolve 1.00g of Soluble Purified Starch in 2.5mLof the buffer solution by warming,transfer to a 100-mLvolumetric flask,add water to volume,and mix.Add 0.50mLof this solution to a 100-mLvolumetric flask containing about 75mLof water,1mLof 1Nhydrochloric acid,and 1.5mLof 0.020Niodine,swirling the flask during the addition.Add water to volume,mix,and allow to stand in the dark for 1hour.The absorbance of this solution,measured at 575nm in a 1-cm cell against a blank,is between 0.5and 0.6.
Reducing substances— Shake 10.0g with 100mLof water for 15minutes,and allow to settle for about 12hours.Filter a portion of the supernatant through fine sintered glass.To 50mLof the filtrate add 50mLof alkaline cupric tartrate TS,and boil for 1to 2minutes.Filter the resulting cuprous oxide,wash it with hot water and then with alcohol,and dry it at 105for 2hours:not more than 47mg is found,corresponding to 0.7%of reducing sugars as maltose.
Loss on drying á731ñ— Dry it at 105for 2hours:it loses not more than 10%of its weight.
Residue on ignition á281ñ: not more than 0.5%.

Stearic Acid, C18H36O2—284.48—Hard,white crystals or amorphous,white powder.Freely soluble in chloroform and in ether;soluble in alcohol and in solvent hexane.
Congealing temperature á651ñ: between 67and 69.
Acid value á401ñ: between 196and 199.
Iodine value á401ñ: not more than 1.
Saponification value á401ñ: between 197and 200.
Palmitic acid— Determine as directed in the Assayunder Stearic Acid(NFmonograph):not more than 5.0%is found.

Stearyl Alcohol (1-Octadecanol), C18H38O—270.49—White flakes,granules,or crystals.Insoluble in water;soluble in alcohol,in ether,in acetone,and in benzene.
Melting range á741ñ: between 56and 58.
Other requirements— It conforms to the tests for Acid value,Iodine value,and Hydroxyl valueunder Stearyl Alcohol(NFmonograph).

Stronger Ammonia Water —See Ammonia Water,Stronger.

Strontium Acetate, Sr(CH3COO)2·(1/2)H2O—214.72—White,crystalline powder.Soluble in 3parts of water;slightly soluble in alcohol.
Assay— Ignite about 3g,accurately weighed,in a platinum crucible,protecting from sulfur in the flame.Cool,transfer the crucible with the residue to a beaker,and add 50mLof water and 40.0mLof 1Nhydrochloric acid VS.Boil gently for 30minutes or longer,if necessary,filter,wash with hot water until the washings are neutral,add methyl red TS,and titrate the excess acid with 1Nsodium hydroxide VS.Each mLof 1Nhydrochloric acid is equivalent to 107.4mg of Sr(CH3COO)2·½H2O:not less than 99%is found.
Insoluble matter(Reagent test): not more than 2mg,from 10g (0.02%).
Free alkalior free acid— Dissolve 3g in 30mLof water,and add 3drops of phenolphthalein TS:no pink color is produced.Titrate with 0.1Nsodium hydroxide VSto a pink color:not more than 0.30mLof the 0.1Nsodium hydroxide is required.
Barium— Dissolve 1g in 10mLof water,and add 1drop of glacial acetic acid and 5drops of potassium dichromate solution (1in 10):no turbidity is produced within 2minutes (about 0.02%).
Calcium— Ignite 1g until completely carbonized.Warm the residue with a mixture of 3mLof nitric acid and 10mLof water,filter,wash with 5mLof water,and evaporate the filtrate on a steam bath to dryness.Powder the residue,and dry it at 120for 3hours.Reflux the dried powder with 15mLof dehydrated alcohol for 10minutes,cool in ice,and filter.Repeat the extraction with 10mLof dehydrated alcohol.Evaporate the combined filtrates to dryness,add 0.5mLof sulfuric acid,and ignite:the weight of the residue is not more than 10mg (0.3%of Ca).
Chloride(Reagent test)— One g shows not more than 0.1mg of Cl (0.01%).
Heavy metals(Reagent test): 0.001%.
Iron á241ñ— Dissolve 1.0g in 45mLof water,and add 2mLof hydrochloric acid:the solution shows not more than 0.01mg of Fe (0.001%).
Alkali salts— Dissolve 2g in 80mLof water,heat to boiling,add an excess of ammonium carbonate TS,boil for 5minutes,dilute with water to 100mL,and filter.Evaporate 50mLof the filtrate,and ignite:the residue after correcting for the ignition residue from half the volume of the clear ammonium carbonate TSused above,is not more than 3mg (0.3%).
Nitrate— Dissolve 1g in 10mLof water,add 0.10mLof indigo carmine TS,and then add 10mLof sulfuric acid:the blue color persists for 5minutes (about 0.01%of NO3).

Strontium Hydroxide (Strontium Hydroxide Octahydrate), Sr(OH)2·8H2O—265.76—White,crystalline,free-flowing powder.Sparingly soluble in water.May absorb carbon dioxide from the air.Keep tightly closed.
Assayand carbonate— Accurately weigh about 5g,dissolve in 200mLof warm carbon dioxide-free water in a glass-stoppered,500-mLflask,add phenolphthalein TS,and titrate with 1Nhydrochloric acid VSto determine the hydroxide alkalinity.Then add methyl orange TS,and titrate with 1Nhydrochloric acid VS.Each mLof 1Nhydrochloric acid required to reach the phenolphthalein endpoint is equivalent to 132.9mg of Sr(OH)2·8H2O,and each additional mLof 1Nhydrochloric acid VSrequired to reach the methyl orange endpoint is equivalent to 73.8mg of SrCO3.Not less than 95.0%of Sr(OH)2·8H2Oand not more than 3.0%of SrCO3are found.
Chloride(Reagent test)— Dissolve 1.0g in 100mLof water,and filter if necessary:1.0mLof the solution shows not more than 0.01mg of Cl (0.1%).
Calcium(Reagent test)— Dissolve 5.0g in water,and dilute with water to 100mL,to obtain the test solution.
SAMPLE SOLUTION— Dilute 10.0mLof test solutionwith water to 100mL.
CONTROL SOLUTION— To 10.0mLof test solutionadd 0.50mg of calcium ion (Ca),and dilute with water to 100mL.
PROCEDURE— Determine the background emission at 416.7nm:the limit is 0.1%.
Iron— Dissolve 1g in warm water,and dilute with water to 100mL.To 20mLof this solution add 2mLof hydrochloric acid and 0.1mLof 0.1Npotassium permanganate,allow to stand for 5minutes,and add 3mLof ammonium thiocyanate solution (3in 10).Any red color produced is not darker than that of a control containing 0.03mg of added Fe (0.015%).
For the following test,prepare a test solutionas follows.Dissolve 2.0g in 14mLof dilute hydrochloric acid (1in 6),and evaporate on a steam bath to dryness.Take up the residue in 25mLof water,filter,and dilute with water to 100mL.
Heavy metals— To 5.0mLof test solutionadd 0.02mg of lead (Pb),and dilute with water to 30mL,to provide the standard.For the test specimen,use 30mLof test solution.Adjust each solution with diluted acetic acid or ammonia TSto a pHbetween 3.0and 4.0(using short-range pHpaper),dilute with water to 40mL,and add 10mLof freshly prepared hydrogen sulfide TS:any brown color developed in the sample solution is not darker than that in the control solution (0.004%).

Strychnine Sulfate, (C21H22N2O2)2·H2SO4·5H2O—856.98—Colorless or white crystals,or a white,crystalline powder.Its solutions are levorotatory.One g dissolves in about 35parts of water,in 85mLof alcohol,and in about 220mLof chloroform.Insoluble in ether.
Solubility— Asolution of 500mg in 25mLof water is complete,clear,and colorless.
Residue on ignition(Reagent test): not more than 0.1%.
Brucine— To 100mg add 1mLof dilute nitric acid (1in 2):a yellow color may be observed,but not a red or reddish-brown color.

Styrene-Divinylbenzene Copolymer Beads —Neutral,porous,cross-linked beads,200–400mesh,molecular weight operating range up to 2,000(based on beads fully swollen in benzene).Suitable for use in the gel permeation separation of lipophilic polymers and other solutes requiring organic eluant.
[NOTE—Asuitable grade is available commercially as “BioBeads S-X”from Bio-Rad,www.bio-rad.com.]

Styrene-Divinylbenzene Anion-exchange Resin,50-to 100-Mesh —See Anion-exchange Resin,50-to 100-Mesh,Styrene-Divinylbenzene.

Styrene-Divinylbenzene Cation-exchange Resin,Strongly Acidic —See Cation-exchange Resin,Styrene-Divinylbenzene,Strongly Acidic.

Succinic Acid, C4H6O4—118.09[771-50-6]—Use ACSreagent grade.

Sudan III, C22H16N4O—352.39—Red to red-brown powder.Use a suitable grade.
Assay— When tested by thin-layer chromatography (see Chromatography á621ñ)with the use of plates coated with chromatographic silica gel mixture and a developing system consisting of a mixture of hexane and ethyl acetate (80:20),and examined under short-wavelength UVlight,a single spot is exhibited,with trace impurities.

Sudan IV, C24H20N4O—380.44—Brown to reddish-brown powder.
Assay— Transfer about 25mg,accurately weighed,to a 100-mLvolumetric flask.Dissolve in chloroform,dilute with chloroform to volume,and mix.Dilute 2.0mLof the resulting solution with chloroform to 50.0mL.Determine the absorbance of this solution in 1-cm cells at the wavelength of maximum absorbance at about 520nm,with a suitable spectrophotometer,using chloroform as the blank.Calculate the percentage of Sudan IVin the test specimen taken by the formula:
(100A)/(85C),
in which Ais the absorbance at 520nm and Cis the concentration of the test specimen in g per liter.Not less than 90%is found.
Loss on drying á731ñ— Dry it at 105for 2hours:it loses not more than 10%of its weight.

Sulfamic Acid, HSO3NH2—97.09—Use ACSreagent grade.

Sulfanilamide, C6H8N2O2S—172.21—Use USP Sulfanilamide Melting Point RS.

Sulfanilic Acid, p-NH2C6H4SO3H·H2O—191.21—Use ACSreagent grade.

Sulfatase Enzyme Preparation —Use a suitable grade.
[NOTE—Asuitable grade is available commercially under catalog number S-9626from Sigma-Aldrich,Web site:www.sigma-aldrich.com.]

Sulfathiazole Sodium (4-Amino-N-2-thiazolylbenzenesulfonamide Sodium Salt), C9H8N3NaO2S2—277.29[144-74-1]—Use a suitable grade.

Sulfonic Acid Cation-exchange Resin —See Cation-exchange Resin,Sulfonic Acid.

Sulfosalicylic Acid, C6H3(COOH)(OH)(SO3H)-1,2,5·2H2O—254.22—Use ACSreagent grade.

Sulfur —Use Precipitated Sulfur(USPmonograph).

Sulfur Dioxide Detector Tube— Afuse-sealed glass tube so designed that gas may be passed through it and containing suitable absorbing filters and support media for an iodine-starch indicator.
Measuring range: 1to 25ppm.
[NOTE—Available from Draeger Safety,Inc.,www.draeger.com,or from Gastec Corp.,www.gastec.co.jp,distributed in the USAby www.nextteq.com.]

Sulfuric Acid, H2SO4—98.08—Use ACSreagent grade.

Sulfuric Acid,Diluted (10percent)—Cautiously add 57mLof sulfuric acid to about 100mLof water,cool to room temperature,and dilute with water to 1000mL.

Sulfuric Acid,Fluorometric —Use ACSreagent grade Sulfuric Acid that conforms to the following additional test:
Fluorescence— Using a suitable fluorometer having a sharp cut-off 360-nm excitation filter and a sharp cut-off 415-nm excitation filter,determine the fluorescence of the sulfuric acid in a cuvette previously rinsed with water followed by several portions of the acid under examination:the fluorescence does not exceed that of quinine sulfate solution (1in 1,600,000,000),similarly measured.

Sulfuric Acid,Fuming, H2SO4plus free SO3having a nominal content of 15%,20%,or 30%of free SO3—Use ACSreagent grade (containing between 15.0%and 18.0%,between 20.0%and 23.0%,or between 30.0%and 33.0%of free SO3).

Sulfurous Acid, H2SO3—82.08—Awater solution of sulfur dioxide—Use ACSreagent grade.

Supports for Gas Chromatography —See supports for gas chromatography in the Chromatographic Reagentssection under Chromatography á621ñ.