Add 116mLof glacial acetic acid to sufficient water to make 1000mLafter cooling to room temperature.

Dissolve about 8g of ammonium thiocyanate in 1000mLof water,and standardize the solution as follows.

Measure accurately about 30mLof 0.1Nsilver nitrate VSinto a glass-stoppered flask.Dilute with 50mLof water,then add 2mLof nitric acid and 2mLof ferric ammonium sulfate TS,and titrate with the ammonium thiocyanate solution to the first appearance of a red-brown color.Calculate the normality.

If desirable,0.1Nammonium thiocyanate may be replaced by 0.1Npotassium thiocyanate where the former is directed in various tests and assays.

Dissolve 3g of potassium bromate and 15g of potassium bromide in water to make 1000mL,and standardize the solution as follows.

Measure accurately about 25mLof the solution into a 500-mLiodine flask,and dilute with 120mLof water.Add 5mLof hydrochloric acid,insert the stopper in the flask,and shake it gently.Then add 5mLof potassium iodide TS,again insert the stopper,shake the mixture,allow it to stand for 5minutes,and titrate the liberated iodine with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Calculate the normality.

Preserve in dark amber-colored,glass-stoppered bottles.

Dissolve 2.75g of ceric ammonium nitrate in 1Nnitric acid to obtain 100mLof solution,and filter.Standardize the solution as follows.

Measure accurately 10mLof freshly standardized 0.1Nferrous ammonium sulfate VSinto a flask,and dilute with water to about 100mL.Add 1drop of nitrophenanthroline TS,and titrate with the ceric ammonium nitrate solution to a colorless endpoint.From the volume of 0.1Nferrous ammonium sulfate VStaken and the volume of ceric ammonium nitrate solution consumed,calculate the normality.

Transfer 59g of ceric ammonium nitrate to a beaker,add 31mLof sulfuric acid,mix,and cautiously add water,in 20-mLportions,until solution is complete.Cover the beaker,allow to stand overnight,filter through a fine-porosity,sintered-glass crucible,dilute with water to 1000mL,and mix.Standardize the solution as follows.[NOTE—Prepare the osmium tetroxide solution used in this procedure in a well-ventilated hood,as poisonous vapors are given off by this compound.]Weigh accurately 200mg of arsenic trioxide,previously dried at 105for 1hour,and transfer to a 500-mLconical flask.Wash down the inner walls of the flask with 25mLof sodium hydroxide solution (2in 25),swirl to dissolve the substance,and when solution is complete,add 100mLof water,and mix.Add 10mLof dilute sulfuric acid (1in 3),then add 2drops each of orthophenanthroline TSand a 1in 400solution of osmium tetroxide in 0.1Nsulfuric acid,and slowly titrate with the ceric sulfate solution until the pink color is changed to a very pale blue.Calculate the normality.Each 4.946mg of arsenic trioxide is equivalent to 1mLof 0.1Nceric sulfate.

Dissolve 23.3g of cupric nitrate 2.5hydrate,or 24.2g of the trihydrate,in water to make 1000mL.Standardize the solution as follows.

Transfer 20.0mLof the solution to a 250-mLbeaker.Add 2mLof 5Msodium nitrate,20mLof ammonium acetate TS,and sufficient water to make 100mL.Titrate with 0.05Medetate disodium VS.Determine the endpoint potentiometrically using a cupric ion-double junction reference electrode system.Perform a blank determination,and make any necessary correction.Calculate the normality by the formula:

in which Vis the volume,in mL,of edetate disodium consumed,Mis the molarity of the edetate disodium,and 20.0is the number of mLof cupric nitrate solution taken.

To 50mg of 2,6-dichlorophenol-indophenol sodium that has been stored in a desiccator over soda lime add 50mLof water containing 42mg of sodium bicarbonate,shake vigorously,and when the dye is dissolved,add water to make 200mL.Filter into an amber,glass-stoppered bottle.Standardize the solution as follows.

Accurately weigh 50mg of USP Ascorbic Acid RS,and transfer to a glass-stoppered,50-mLvolumetric flask with the aid of a sufficient volume of metaphosphoric-acetic acids TSto make 50mL.Immediately transfer 2mLof the ascorbic acid solution to a 50-mLconical flask containing 5mLof the metaphosphoric-acetic acids TS,and titrate rapidly with the dichlorophenol-indophenol solution until a distinct rose-pink color persists for at least 5seconds.Perform a blank titration by titrating 7mLof the metaphosphoric-acetic acids TSplus a volume of water equal to the volume of the dichlorophenol solution used in titrating the ascorbic acid solution.Express the concentration of the standard solution in terms of its equivalent in mg of ascorbic acid.

Dissolve 18.6g of edetate disodium in water to make 1000mL,and standardize the solution as follows.

Accurately weigh about 200mg of chelometric standard calcium carbonate,previously dried at 110for 2hours and cooled in a desiccator,transfer to a 400-mLbeaker,add 10mLof water,and swirl to form a slurry.Cover the beaker with a watch glass,and introduce 2mLof diluted hydrochloric acid from a pipet inserted between the lip of the beaker and the edge of the watch glass.Swirl the contents of the beaker to dissolve the calcium carbonate.Wash down the sides of the beaker,the outer surface of the pipet,and the watch glass with water,and dilute with water to about 100mL.While stirring the solution,preferably with a magnetic stirrer,add about 30mLof the edetate disodium solution from a 50-mLburet.Add 15mLof sodium hydroxide TSand 300mg of hydroxy naphthol blue,and continue the titration with the edetate disodium solution to a blue endpoint.Calculate the molarity taken by the formula:

in which Wis the weight,in mg,of CaCO3in the portion of calcium carbonate taken,and Vis the volume,in mL,of edetate disodium solution consumed.

Dissolve 50g of ferric ammonium sulfate in a mixture of 300mLof water and 6mLof sulfuric acid,dilute with water to 1000mL,and mix.Standardize the solution as follows.

Measure accurately about 40mLof the solution into a glass-stoppered flask,add 5mLof hydrochloric acid,mix,and add a solution of 3g of potassium iodide in 10mLof water.Insert the stopper,allow to stand for 10minutes,then titrate the liberated iodine with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Correct for a blank run on the same quantities of the same reagents,and calculate the normality.

Store in tight containers,protected from light.

Dissolve 40g of ferrous ammonium sulfate in a previously cooled mixture of 40mLof sulfuric acid and 200mLof water,dilute with water to 1000mL,and mix.On the day of use,standardize the solution as follows.

Measure accurately 25to 30mLof the solution into a flask,add 2drops of orthophenanthroline TS,and titrate with 0.1Nceric sulfate VSuntil the red color is changed to pale blue.From the volume of 0.1Nceric sulfate consumed,calculate the normality.

Dilute 85mLof hydrochloric acid with water to 1000mL.Standardize the solution as follows.

Accurately weigh about 5.0g of tromethamine,previously dried at 105for 3hours.Dissolve in 50mLof water,and add 2drops of bromocresol green TS.Titrate with 1Nhydrochloric acid to a pale yellow endpoint.Calculate the normality.Each 121.14mg of tromethamine is equivalent to 1mLof 1Nhydrochloric acid.

To a 1000-mLvolumetric flask containing 40mLof water slowly add 43mLof hydrochloric acid.Cool,and add methanol to volume.Standardize the solution as follows.

Weigh accurately about 2.5g of tromethamine,previously dried at 105for 3hours.Proceed as directed under Hydrochloric Acid,Normal(1N),beginning with “Dissolve in 50mLof water.”

Dissolve about 14g of iodine in a solution of 36g of potassium iodide in 100mLof water,add 3drops of hydrochloric acid,dilute with water to 1000mL,and standardize the solution as follows.

Transfer 25.0mLof the iodine solution to a 250-mLflask,dilute with water to 100mL,add 1mLof 1Nhydrochloric acid,swirl gently to mix,and titrate with 0.1Nsodium thiosulfate VSuntil the solution has a pale yellow color.Add 2mLof starch TSand continue titrating until the solution is colorless.Calculate the normality.

Preserve in amber-colored,glass-stoppered bottles.

Dissolve about 1.4g of iodine in a solution of 3.6g of potassium iodide in 100mLof water,add 3drops of hydrochloric acid,dilute with water to 1000mL,and standardize the solution as follows.

Transfer 100.0mLof iodine solution to a 250-mLflask,add 1mLof 1Nhydrochloric acid,swirl gently to mix,and titrate with 0.1Nsodium thiosulfate VSuntil the solution has a pale yellow color.Add 2mLof starch TS,and continue titrating until the solution is colorless.Calculate the normality.

Preserve in amber-colored,glass-stoppered bottles.

Accurately pipet 100mLof commercially available 0.1Mlead perchlorate solution into a 1000-mLvolumetric flask,add a sufficient quantity of water to make 1000mL,and standardize the solution as follows.

Accurately pipet 50mLof 0.01Mlead perchlorate solution,as prepared above,into a 250-mLconical flask.Add 3mLof aqueous hexamethylenetetramine solution (2.0g per 100mL)and 4drops of 0.5%xylenol orange indicator prepared by adding 500mg of xylenol orange to 10mLof alcohol and diluting with water to 100mL.(Omit the alcohol if the sodium salt of the indicator is used).Titrate with 0.05Medetate disodium VSto a yellow endpoint.Calculate the molarity.

Dissolve 0.12g of freshly cut lithium metal in 150mLof methanol,cooling the flask during addition of the metal.When the reaction is complete,add 850mLof methanol,and mix.Store the solution preferably in the reservoir of an automatic delivery buret suitably protected from carbon dioxide and moisture.Standardize the solution by titration against benzoic acid as described under Sodium Methoxide,Tenth-Normal (0.1N)(in Toluene),but use only 100mg of benzoic acid.Each 2.442mg of benzoic acid is equivalent to 1mLof 0.02Nlithium methoxide.

[NOTE—Restandardize the solution frequently.]

Dissolve 0.6g of freshly cut lithium metal in 150mLof methanol,cooling the flask during addition of the metal.When reaction is complete,add 850mLof benzene.If cloudiness or precipitation occurs,add sufficient methanol to clarify the solution.Store preferably in the reservoir of an automatic delivery buret suitably protected from carbon dioxide and moisture.Standardize the solution by titration against benzoic acid as described under Sodium Methoxide,Tenth-Normal (0.1N)(in Toluene).

[NOTE—Restandardize the solution frequently.]

Dissolve 0.7g of freshly cut lithium metal in 150mLof methanol,cooling the flask during addition of the metal.When reaction is complete,add 850mLof chlorobenzene.If cloudiness or precipitation occurs,add sufficient methanol to clarify the solution.Store preferably in the reservoir of an automatic delivery buret suitably protected from carbon dioxide and moisture.Standardize the solution by titration against benzoic acid as described under Sodium Methoxide,Tenth-Normal(0.1N)(in Toluene).

[NOTE—Restandardize the solution frequently.]

Dissolve about 35g of mercuric nitrate in a mixture of 5mLof nitric acid and 500mLof water,and dilute with water to 1000mL.Standardize the solution as follows.

Transfer an accurately measured volume of about 20mLof the solution to a conical flask,and add 2mLof nitric acid and 2mLof ferric ammonium sulfate TS.Cool to below 20,and titrate with 0.1Nammonium thiocyanate VSto the first appearance of a permanent brownish color.Calculate the molarity.

Transfer 44mLof recently distilled morpholine to a 1-liter reagent bottle,and add methanol to make about 1liter.Protect from absorption of carbon dioxide during withdrawal of aliquots.It is not necessary to standardize this solution.

Dissolve 6.45g of oxalic acid in water to make 1000mL.Standardize by titration against freshly standardized 0.1Npotassium permanganate VSas directed under Potassium Permanganate,Tenth-Normal(0.1N).

Preserve in glass-stoppered bottles,protected from light.

[NOTE—Where called for in the tests and assays,this volumetric solution is specified as “0.1Nperchloric acid.”Thus,where 0.1Nor other strength of this volumetric solution is specified,the solution in glacial acetic acid is to be used,unless the words “in dioxane”are stated.[See also Perchloric Acid,Tenth-Normal(0.1N)in Dioxane.]]

Mix 8.5mLof perchloric acid with 500mLof glacial acetic acid and 21mLof acetic anhydride,cool,and add glacial acetic acid to make 1000mL.Alternatively,the solution may be prepared as follows.Mix 11mLof 60percent perchloric acid with 500mLof glacial acetic acid and 30mLof acetic anhydride,cool,and add glacial acetic acid to make 1000mL.

Allow the prepared solution to stand for 1day for the excess acetic anhydride to be combined,and determine the water content by Method I(see Water Determination á921ñ),except to use a test specimen of about 5g of the 0.1Nperchloric acid that is expected to contain approximately 1mg of water and the Reagent(see Reagentunder Method Iain Water Determination á921ñ)diluted such that 1mLis equivalent to about 1to 2mg of water.If the water content exceeds 0.5%,add more acetic anhydride.If the solution contains no titratable water,add sufficient water to obtain a content of between 0.02%and 0.5%of water.Allow the solution to stand for 1day,and again titrate the water content.The solution so obtained contains between 0.02%and 0.5%of water,indicating freedom from acetic anhydride.

Standardize the solution as follows.

Weigh accurately about 700mg of potassium biphthalate,previously crushed lightly and dried at 120for 2hours,and dissolve it in 50mLof glacial acetic acid in a 250-mLflask.Add 2drops of crystal violet TS,and titrate with the perchloric acid solution until the violet color changes to blue-green.Deduct the volume of the perchloric acid consumed by 50mLof the glacial acetic acid,and calculate the normality.Each 20.42mg of potassium biphthalate is equivalent to 1mLof 0.1Nperchloric acid.

Mix 8.5mLof perchloric acid with sufficient dioxane to make 1000mL.Standardize the solution as follows.

Weigh accurately about 700mg of potassium biphthalate,previously crushed lightly and dried at 120for 2hours,and dissolve in 50mLof glacial acetic acid in a 250-mLflask.Add 2drops of crystal violet TS,and titrate with the perchloric acid solution until the violet color changes to bluish green.Deduct the volume of the perchloric acid consumed by 50mLof the glacial acetic acid,and calculate the normality.Each 20.42mg of potassium biphthalate is equivalent to 1mLof 0.1Nperchloric acid.

Dissolve 4.9455g of arsenic trioxide primary standard,previously dried at 105for 1hour,in 75mLof 1Npotassium hydroxide.Add 40g of potassium bicarbonate,dissolved in about 200mLof water,and dilute with water to 1000.0mL.

Dissolve 2.784g of potassium bromate in water to make 1000mL,and standardize the solution as follows.

Transfer an accurately measured volume of about 40mLof the solution to a glass-stoppered flask,add 3g of potassium iodide,and follow with 3mLof hydrochloric acid.Allow to stand for 5minutes,then titrate the liberated iodine with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Correct for a blank run on the same quantities of the same reagents,and calculate the normality.

Dissolve 2.78g of potassium bromate (KBrO3)and 12.0g of potassium bromide (KBr)in water,and dilute with water to 1000mL.Standardize by the procedure set forth for Potassium Bromate,Tenth-Normal(0.1N).

Dissolve about 5g of potassium dichromate in 1000mLof water.Standardize the solution as follows.

Transfer 25.0mLof this solution to a glass-stoppered,500-mLflask,add 2g of potassium iodide (free from iodate),dilute with 200mLof water,add 5mLof hydrochloric acid,allow to stand for 10minutes in a dark place,and titrate the liberated iodine with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Correct for a blank run on the same quantities of the same reagents,and calculate the normality.

Dissolve about 17g of potassium ferricyanide in water to make 1000mL.Standardize the solution as follows.

Transfer 50.0mLof this solution to a glass-stoppered,500-mLflask,dilute with 50mLof water,add 10mLof potassium iodide TSand 10mLof dilute hydrochloric acid,and allow to stand for 1minute.Then add 15mLof zinc sulfate solution (1in 10),and titrate the liberated iodine with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Calculate the molarity.

Protect from light,and restandardize before use.

Dissolve 68g of potassium hydroxide in about 950mLof water.Add a freshly prepared saturated solution of barium hydroxide until no more precipitate forms.Shake the mixture thoroughly,and allow it to stand overnight in a stoppered bottle.Decant the clear liquid,or filter the solution in a tight,polyolefin bottle,and standardize by the procedure set forth for Sodium Hydroxide,Normal(1N).

Dissolve about 34g of potassium hydroxide in 20mLof water,and add aldehyde-free alcohol to make 1000mL.Allow the solution to stand in a tightly stoppered bottle for 24hours.Then quickly decant the clear supernatant liquid into a suitable,tight container,and standardize the solution as follows.

Measure accurately about 25mLof 0.5Nhydrochloric acid VS.Dilute with 50mLof water,add 2drops of phenolphthalein TS,and titrate with the alcoholic potassium hydroxide solution until a permanent,pale pink color is produced.Calculate the normality.

[NOTE—Store in tightly stoppered bottles,protected from light.]

Dissolve about 6.8g of potassium hydroxide in 4mLof water,and add methanol to make 1000mL.Allow the solution to stand in a tightly stoppered bottle for 24hours.Then quickly decant the clear supernatant liquid into a suitable,tight container,and standardize the solution as follows.

Measure accurately about 25mLof 0.1Nhydrochloric acid VS.Dilute with 50mLof water,add 2drops of phenolphthalein TS,and titrate with the methanolic potassium hydroxide solution until a permanent,pale pink color is produced.Calculate the normality.

[NOTE—Store in tightly stoppered bottles,protected from light.]

Dissolve 10.700g of potassium iodate,previously dried at 110to constant weight,in water to make 1000.0mL.

Dissolve about 3.3g of potassium permanganate in 1000mLof water in a flask,and boil the solution for about 15minutes.Insert the stopper in the flask,allow it to stand for at least 2days,and filter through a fine-porosity,sintered-glass crucible.If necessary,the bottom of the sintered-glass crucible may be lined with a pledget of glass wool.Standardize the solution as follows.

Accurately weigh about 200mg of sodium oxalate,previously dried at 110to constant weight,and dissolve it in 250mLof water.Add 7mLof sulfuric acid,heat to about 70,and then slowly add the permanganate solution from a buret,with constant stirring,until a pale pink color,which persists for 15seconds,is produced.The temperature at the conclusion of the titration should be not less than 60.Calculate the normality.Each 6.700mg of sodium oxalate is equivalent to 1mLof 0.1Npotassium permanganate.

Since potassium permanganate is reduced on contact with organic substances such as rubber,the solution must be handled in apparatus entirely of glass or other suitably inert material.It should be frequently restandardized.Store in glass-stoppered,amber-colored bottles.

Dissolve about 17.5g of silver nitrate in 1000mLof water,and standardize the solution as follows.

Transfer about 100mg,accurately weighed,of reagent-grade sodium chloride,previously dried at 110for 2hours,to a 150-mLbeaker,dissolve in 5mLof water,and add 5mLof acetic acid,50mLof methanol,and about 0.5mLof eosin Y TS.Stir,preferably with a magnetic stirrer,and titrate with the silver nitrate solution.Calculate the normality.

Transfer 4.9455g of arsenic trioxide,which has been pulverized and dried at 100to constant weight,to a 1000-mLvolumetric flask,dissolve it in 40mLof 1Nsodium hydroxide,and add 1Nsulfuric acid or 1Nhydrochloric acid until the solution is neutral or only slightly acid to litmus.Add 30g of sodium bicarbonate,dilute with water to volume,and mix.

Dissolve 162g of sodium hydroxide in 150mLof carbon dioxide-free water,cool the solution to room temperature,and filter through hardened filter paper.Transfer 54.5mLof the clear filtrate to a tight,polyolefin container,and dilute with carbon dioxide-free water to 1000mL.

Accurately weigh about 5g of potassium biphthalate,previously crushed lightly and dried at 120for 2hours,and dissolve in 75mLof carbon dioxide-free water.Add 2drops of phenolphthalein TS,and titrate with the sodium hydroxide solution to the production of a permanent pink color.Each 204.2mg of potassium biphthalate is equivalent to 1mLof 1Nsodium hydroxide.

[NOTES—(1)Solutions of alkali hydroxides absorb carbon dioxide when exposed to air.They should be preserved in bottles having well-fitted,suitable stoppers,provided with a tube filled with a mixture of sodium hydroxide and lime (soda-lime tubes)so that air entering the container must pass through this tube,which will absorb the carbon dioxide.(2)Prepare solutions of lower concentration (e.g.,0.1N,0.01N)by quantitatively diluting accurately measured volumes of the 1Nsolution with sufficient carbon dioxide-free water to yield the desired concentration.]

Restandardize the solution frequently.

To 250mLof alcohol add 2mLof a 50%(w/w)solution of sodium hydroxide.

Dissolve about 200mg of benzoic acid,accurately weighed,in 10mLof alcohol and 2mLof water.Add 2drops of phenolphthalein TS,and titrate with the alcoholic sodium hydroxide solution until a permanent pale pink color is produced.Calculate the normality as follows:

in which Wis the weight,in mg,of benzoic acid taken,Vis the volume,in mL,of alcoholic sodium hydroxide consumed,and 122.12is the molecular weight of benzoic acid.

Cool in ice-water 150mLof methanol contained in a 1000-mLvolumetric flask,and add,in small portions,about 2.5g of freshly cut sodium metal.When the metal has dissolved,add toluene to make 1000mL,and mix.Store preferably in the reservoir of an automatic delivery buret suitably protected from carbon dioxide and moisture.Standardize the solution as follows.

Accurately weigh about 400mg of primary standard benzoic acid,and dissolve in 80mLof dimethylformamide in a flask.Add 3drops of a 1in 100solution of thymol blue in dimethylformamide,and titrate with the sodium methoxide to a blue endpoint.Correct for the volume of the sodium methoxide solution consumed by 80mLof the dimethylformamide,and calculate the normality.Each 12.21mg of benzoic acid is equivalent to 1mLof 0.1Nsodium methoxide.

[NOTES—(1)To eliminate any turbidity that may form following dilution with toluene,add methanol (25to 30mLusually suffices)until the solution is clear.(2)Restandardize the solution frequently.]

Weigh 11.5g of freshly cut sodium metal,and cut into small cubes.Place about 0.5mLof anhydrous methanol in a round-bottom,250-mLflask equipped with a ground-glass joint,add 1cube of the sodium metal,and,when the reaction has ceased,add the remaining sodium metal to the flask.Connect a water-jacketed condenser to the flask,and slowly add 250mLof anhydrous methanol,in small portions,through the top of the condenser.Regulate the addition of the methanol so that the vapors are condensed and do not escape through the top of the condenser.After addition of the methanol is complete,connect a drying tube to the top of the condenser,and allow the solution to cool.Transfer the solution to a 1-liter volumetric flask,dilute with anhydrous methanol to volume,and mix.Standardize the solution as follows.

Measure accurately about 20mLof freshly standardized 1Nhydrochloric acid VSinto a 250-mLconical flask,add 0.25mLof phenolphthalein TS,and titrate with the sodium methoxide solution to the first appearance of a permanent pink color.Calculate the normality.

Dissolve 7.5g of sodium nitrite in water to make 1000mL,and standardize the solution as follows.

Accurately weigh about 500mg of USP Sulfanilamide RS,previously dried at 105for 3hours,and transfer to a suitable beaker.Add 20mLof hydrochloric acid and 50mLof water,stir until dissolved,and cool to 15.Maintaining the temperature at about 15,titrate slowly with the sodium nitrite solution,placing the buret tip below the surface of the solution to preclude air oxidation of the sodium nitrite,and stir the solution gently with a magnetic stirrer,but avoid pulling a vortex of air beneath the surface.Use the indicator specified in the individual monograph,or,if a potentiometric procedure is specified,determine the endpoint electrometrically,using platinum-calomel or platinum-platinum electrodes.When the titration is within 1mLof the endpoint,add the titrant in 0.1-mLportions,and allow 1minute between additions.Calculate the molarity.Each 17.22mg of sulfanilamide is equivalent to 1mLof 0.1000Msodium nitrite.

Dissolve an amount of sodium tetraphenylboron,equivalent to 6.845g of NaB(C6H5)4,in water to make 1000mL,and standardize the solution as follows.

Pipet two 75-mLportions of the solution into separate beakers,and to each add 1mLof acetic acid and 25mLof water.To each beaker add,slowly and with constant stirring,25mLof potassium biphthalate solution (1in 20),and allow to stand for 2hours.Filter one of the mixtures through a filtering crucible,and wash the precipitate with cold water.Transfer the precipitate to a container,add 50mLof water,shake intermittently for 30minutes,filter,and use the filtrate as the saturated potassium tetraphenylborate solution in the following standardization procedure.Filter the second mixture through a tared filtering crucible,and wash the precipitate with three 5-mLportions of saturated potassium tetraphenylborate solution.Dry the precipitate at 105for 1hour.Each g of potassium tetraphenylborate is equivalent to 955.1mg of sodium tetraphenylboron.From the weight of sodium tetraphenylboron obtained,calculate the molarity of the sodium tetraphenylboron solution.

[NOTE—Prepare this solution fresh.]

Dissolve about 26g of sodium thiosulfate and 200mg of sodium carbonate in 1000mLof recently boiled and cooled water.Standardize the solution as follows.

Accurately weigh about 210mg of primary standard potassium dichromate,previously pulverized and dried at 120for 4hours,and dissolve in 100mLof water in a glass-stoppered,500-mLflask.Swirl to dissolve the solid,remove the stopper,and quickly add 3g of potassium iodide,2g of sodium bicarbonate,and 5mLof hydrochloric acid.Insert the stopper gently in the flask,swirl to mix,and allow to stand in the dark for exactly 10minutes.Rinse the stopper and the inner walls of the flask with water,and titrate the liberated iodine with the sodium thiosulfate solution until the solution is yellowish green in color.Add 3mLof starch TS,and continue the titration until the blue color is discharged.Perform a blank determination.Calculate the normality.

Restandardize the solution as frequently as supported by laboratory stability data.In the absence of such data,restandardize the solution weekly.

Add slowly,with stirring,13.9mLof sulfuric acid to a sufficient quantity of dehydrated alcohol to make 1000mL.Cool,and standardize against tromethamine as described under Hydrochloric Acid,Half-Normal(0.5N)in Methanol.

Add slowly,with stirring,30mLof sulfuric acid to about 1020mLof water,allow to cool to 25,and determine the normality by titration against tromethamine as described under Hydrochloric Acid,Normal(1N).

Dissolve 40g of tetra-n-butylammonium iodide in 90mLof anhydrous methanol in a glass-stoppered flask.Place in an ice bath,add 20g of powdered silver oxide,insert the stopper in the flask,and agitate vigorously for 60minutes.Centrifuge a few mL,and test the supernatant liquid for iodide (see Iodide á191ñ).If the test is positive,add an additional 2g of silver oxide,and continue to allow to stand for 30minutes with intermittent agitation.When all of the iodide has reacted,filter through a fine-porosity,sintered-glass funnel.Rinse the flask and the funnel with three 50-mLportions of anhydrous toluene,adding the rinsings to the filtrate.Dilute with a mixture of three volumes of anhydrous toluene and 1volume of anhydrous methanol to 1000mL,and flush the solution for 10minutes with dry,carbon dioxide-free nitrogen.[NOTE—If necessary to obtain a clear solution,further small quantities of anhydrous methanol may be added.]Store in a reservoir protected from carbon dioxide and moisture,and discard after 60days.Alternatively,the solution may be prepared by diluting a suitable volume of commercially available tetrabutylammonium hydroxide solution in methanol with a mixture of 4volumes of anhydrous toluene and 1volume of anhydrous methanol.[NOTE—If necessary to obtain a clear solution,further small quantities of methanol may be added.]

Standardize the solution on the day of use as follows.Dissolve about 400mg of primary standard benzoic acid,accurately weighed,in 80mLof dimethylformamide,add 3drops of a 1in 100solution of thymol blue in dimethylformamide,and titrate to a blue endpoint with the tetrabutylammonium hydroxide solution,delivering the titrant from a buret equipped with a carbon dioxide absorption trap.Perform a blank determination,and make any necessary correction.Each mLof 0.1Ntetrabutylammonium hydroxide is equivalent to 12.21mg of benzoic acid.

Prepare as described for Tetrabutylammonium Hydroxide,Tenth-Normal (0.1N)using isopropyl alcohol instead of toluene,and standardize as described.Alternatively,the solution may be prepared by diluting a suitable volume of commercially available tetrabutylammonium hydroxide solution in methanol with 4volumes of anhydrous isopropyl alcohol.

Dissolve 15.41g of tetramethylammonium bromide in water to make 1000mL,and standardize the solution as follows.

Transfer an accurately measured volume of about 40mLof the solution to a beaker,add 10mLof diluted nitric acid and 50.0mLof 0.1Nsilver nitrate VS,and mix.Add 2mLof ferric ammonium sulfate TS,and titrate the excess silver nitrate with 0.1Nammonium thiocyanate VS.Calculate the molarity.

Dissolve 10.96g of tetramethylammonium chloride in water to make 1000mL,and standardize the solution as follows.

Transfer an accurately measured volume of about 40mLof the solution to a flask,add 10mLof diluted nitric acid and 50.0mLof 0.1Nsilver nitrate VS,and mix.Add 5mLof nitrobenzene and 2mLof ferric ammonium sulfate TS,shake,and titrate the excess silver nitrate with 0.1Nammonium thiocyanate VS.Calculate the molarity.

Add 75mLof titanium trichloride solution (1in 5)to 75mLof hydrochloric acid,dilute to 1000mL,and mix.Standardize the solution as follows,using the special titration apparatus described.

Apparatus—Store the titanium trichloride solution in the reservoir of a closed-system titration apparatus in an atmosphere of hydrogen.

Use a wide-mouth,500-mLconical flask as the titration vessel,and connect it by means of a tight-fitting rubber stopper to the titration buret,an inlet tube for carbon dioxide,and an exit tube.Arrange for mechanical stirring.All joints must be air-tight.Arrange to have both the hydrogen and the carbon dioxide pass through wash bottles containing titanium trichloride solution (approximately 1in 50)to remove any oxygen.

If the solution to be titrated is to be heated before or during titration,connect the titration flask with an upright reflux condenser through the rubber stopper.

Standardization—Place an accurately measured volume of about 40mLof 0.1Nferric ammonium sulfate VSin the titration flask,and pass in a rapid stream of carbon dioxide until all the air has been removed.Add the titanium trichloride solution from the buret until near the calculated endpoint (about 35mL),then add through the outlet tube 5mLof ammonium thiocyanate TS,and continue the titration until the solution is colorless.Calculate the normality.

Dissolve 14.4g of zinc sulfate in water to make 1liter.Standardize the solution as follows.

Measure accurately about 10mLof 0.05Medetate disodium VSinto a 125-mLconical flask,and add,in the order given,10mLof acetic acid-ammonium acetate buffer TS,50mLof alcohol,and 2mLof dithizone TS.Titrate with the zinc sulfate solution to a clear,rose-pink color.Calculate the molarity.

[NOTE—For many of the reagents mentioned in the foregoing section,the corresponding standards of the 6th edition (1980)of Reagent Chemicals,published by the American Chemical Society,should be consulted.For a limited number of other reagents,the standards are adapted from those appearing in Reagent Chemicals and Standards,5th edition,by Joseph Rosin and copyrighted by the publisher,D.Van Nostrand Co.,Inc.]