L Designations —See packings for high-pressure liquid chromatography in the Chromatographic Reagentssection under Chromatography á621ñ.
Lactose, C12H22O11·H2O—342.30—Use ACSreagent grade.
Alpha Lactose Monohydrate (a-D-Lactose Monohydrate), C12H22O11·H2O—360.31—White powder.The b-D-lactose content is less than 3%.
Assay—
Inject an appropriate derivatized specimen into a gas chromatograph (see Chromatography á621ñ)equipped with a flame-ionization detector,helium being used as the carrier gas.The following conditions have been found suitable:a 0.25-mm ×30-m capillary column coated with a 1-µm layer of phase G2;the injection port temperature is maintained at 250
;the detector temperature is maintained at 280;the column temperature is maintained at 230and programmed to rise 4per minute to 280.The area of the C12H22O11·H2Opeak is not less than 97%of the total peak area.
;the detector temperature is maintained at 280;the column temperature is maintained at 230and programmed to rise 4per minute to 280.The area of the C12H22O11·H2Opeak is not less than 97%of the total peak area.
Beta Lactose (b-D-Lactose), C12H22O11—342.30—White to faint yellow powder.The a-D-lactose content is not more than 35%.
Assay—
Inject an appropriate derivatized specimen into a gas chromatograph (see Chromatography á621ñ)equipped with a flame-ionization detector,helium being used as the carrier gas.The following conditions have been found suitable:a 0.25-mm ×30-m capillary column coated with a 1-µm layer of phase G43;the injection port temperature is maintained at 250;the detector temperature is maintained at 250;the column temperature is maintained at 20and programmed to rise 8per minute to 280.The area of the C12H22O11peak is not less than 99%of the total peak area.
;the detector temperature is maintained at 250;the column temperature is maintained at 20and programmed to rise 8per minute to 280.The area of the C12H22O11peak is not less than 99%of the total peak area.
Lanthanum Alizarin Complexan Mixture —Use a suitable grade.
Lanthanum Chloride, LaCl3·(6–7)H2O—This reagent is available in degrees of hydration ranging from 6to 7molecules of water.Use ACSreagent grade.
Add the following:
Lauryl Dimethyl Amine Oxide
(N,N-Dimethyldodecylamine-N-oxide),C14H31NO[1643-20-5]—229.41—Use a suitable grade.
Lead Acetate, Pb(C2H3O2)2·3H2O—379.33—Use ACSreagent grade.
Lead Acetate Paper— Immerse filter paper weighing about 80g per square meter in a mixture of diluted acetic acid and lead acetate TS(1:10).Remove,dry,and cut into 15-mm ×40-mm strips.
Lead Monoxide (Litharge), PbO—223.20—Heavy,yellowish or reddish-yellow powder.Insoluble in water and in alcohol;soluble in acetic acid,in diluted nitric acid,and in warm solutions of the fixed alkali hydroxides.
Assay—
Accurately weigh about 300mg,freshly ignited in a muffle furnace at 600±50,and dissolve it by warming with 10mLof water and 1mLof glacial acetic acid.Dilute with 75mLof water,heat to boiling,add 50.0mLof 0.1Npotassium dichromate VS,and boil for 2to 3minutes.Cool,transfer to a 200-mLvolumetric flask with the aid of water,dilute with water to volume,mix,and allow to settle.Withdraw 100.0mLof the clear liquid,and transfer to a glass-stoppered flask.Add 10mLof diluted sulfuric acid and 1g of potassium iodide,insert the stopper,mix gently,and allow to stand for 10minutes.Then titrate the liberated iodine,representing the excess of dichromate,with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached:each mLof 0.1Npotassium dichromate is equivalent to 7.440mg of PbO.Not less than 98%is found.
,and dissolve it by warming with 10mLof water and 1mLof glacial acetic acid.Dilute with 75mLof water,heat to boiling,add 50.0mLof 0.1Npotassium dichromate VS,and boil for 2to 3minutes.Cool,transfer to a 200-mLvolumetric flask with the aid of water,dilute with water to volume,mix,and allow to settle.Withdraw 100.0mLof the clear liquid,and transfer to a glass-stoppered flask.Add 10mLof diluted sulfuric acid and 1g of potassium iodide,insert the stopper,mix gently,and allow to stand for 10minutes.Then titrate the liberated iodine,representing the excess of dichromate,with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached:each mLof 0.1Npotassium dichromate is equivalent to 7.440mg of PbO.Not less than 98%is found.
Insoluble in acetic acid—
Dissolve 2g in 30mLof dilute glacial acetic acid (1in 2),boil gently for 5minutes,filter,wash the residue with diluted acetic acid,and dry at 105for 2hours:the residue weighs not more than 10mg (0.5%).
for 2hours:the residue weighs not more than 10mg (0.5%).
Substances not precipitated by hydrogen sulfide—
Completely precipitate the lead from the filtrate obtained in the test for Insoluble in acetic acidby passing hydrogen sulfide into it,filter,and wash the precipitate with 20mLof water.To one-half of the mixed filtrate and washings add 5drops of sulfuric acid,evaporate to dryness,and ignite at 800±25for 15minutes:the residue weighs not more than 5mg (0.5%).
for 15minutes:the residue weighs not more than 5mg (0.5%).
Volatile substances—
Accurately weigh about 5g,and heat strongly in a covered porcelain crucible:it loses not more than 2.0%of its weight.
Lead Nitrate, Pb(NO3)2—331.21—Use ACSreagent grade.
Lead Perchlorate, Pb(ClO4)2·3H2O—460.15—Use ACSreagent grade.
Lead Tetraacetate, C8H12O8Pb—443.38[546-67-8]—Colorless to pinkish crystals.Soluble in hot glacial acetic acid,in chloroform,in nitrobenzene,and in tetrachloroethane.Hydrolyzed by water,producing brown lead dioxide and acetic acid.Unstable in air.
Linalool (3,7-Dimethyl-1,6-octadien-3-ol), C10H18O—154.25[78-70-6]—Use a suitable grade.
Liquid Petrolatum —Use Mineral Oil.
Lithium Chloride, LiCl—42.39—Use ACSreagent grade.
Lithium Hydroxide, LiOH·H2O—41.96—Use ACSreagent grade.
Lithium Metaborate, LiBO2—49.75—Use ACSreagent grade.
Lithium Nitrate, LiNO3—68.95—Colorless crystals.Use a suitable grade labeled to contain not less than 97.0%.
Lithium Perchlorate, LiClO4—106.39—Use ACSreagent grade.
Lithium Sulfate, Li2SO4·H2O—127.96—Use ACSreagent grade.
Lithocholic Acid, C24H40O3—376.57—White powder.
Assay—
When tested by thin-layer chromatography,with the use of plates coated with chromatographic silica gel mixture,a developing system consisting of a mixture of toluene,1,4-dioxane,and acetic acid (15.2:4.2:0.6),and sprayed with a mixture of sulfuric acid and methanol (1:1),heated at 110for 20minutes,and examined visually and under long-wavelength UVlight,a single spot is exhibited.
for 20minutes,and examined visually and under long-wavelength UVlight,a single spot is exhibited.
Litmus —Ablue pigment prepared from various species of RocellaDeCandolle,LecanoraAcharius,or other lichens (Fam.Parmeliaceae).
Description—
Cubes,masses,fragments,or granules,of an indigo blue or deep violet color.Has the combined odor of indigo and violets,and tinges the saliva a deep blue.The indicator substances it contains are soluble in water and less soluble or insoluble in alcohol.
Ash—
It yields not more than 60.0%of ash.
Locust Bean Gum —Agum obtained from the ground endosperms of Ceratonia siliquaLinnéTaub.(Fam.Leguminosae).Use Locust Bean Gum,FCC.
L-Lysine (2,6-Diaminohexanoic Acid), C6H14N2O2—146.19—Crystalline needles or hexagonal plates.Soluble in water;very slightly soluble in alcohol;insoluble in ether.
Test solution:
20mg per mL,in dilute hydrochloric acid (1in 2).
Nitrogen content,Method Iá461ñ:
between 18.88%and 19.44%of Nis found,corresponding to not less than 98.5%of C6H14N2O2,the test specimen previously having been dried at 105for 2hours.
for 2hours.