L Designations See packings for high-pressure liquid chromatography under Reagents, Chromatographic Reagents.
Lactose, C12H22O11·H2O360.31 [64-42-3]Use ACS reagent grade.
Alpha Lactose Monohydrate (-d-Lactose Monohydrate), C12H22O11·H2O360.31White powder. The -d-lactose content is less than 3%.
Assay Inject an appropriate derivatized specimen into a gas chromatograph (see Chromatography621) 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 230 and programmed to rise 4 per minute to 280. The area of the C12H22O11·H2O peak is not less than 97% of the total peak area.
Beta Lactose (-d-Lactose), C12H22O11342.30White to faint yellow powder. The -d-lactose content is not more than 35%.
Assay Inject an appropriate derivatized specimen into a gas chromatograph (see Chromatography621) 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 20 and programmed to rise 8 per minute to 280. The area of the C12H22O11 peak is not less than 99% of the total peak area.
Lanthanum Alizarin Complexan Mixture Use a suitable grade.
Lanthanum Chloride, LaCl3·(67)H2O[10025-84-0]This reagent is available in degrees of hydration ranging from 6 to 7 molecules of water. Use ACS reagent grade.
Lanthanum Oxide, La2O3325.82 [1312-81-8]An almost white, amorphous powder, practically insoluble in water. It dissolves in dilute solutions of mineral acids and absorbs atmospheric carbon dioxide. Use Atomic Absorption Spectroscopy grade.
Lauryl Dimethyl Amine Oxide (N,N-Dimethyldodecylamine-N-oxide),C14H31NO[1643-20-5]229.41Use a suitable grade.
[noteA suitable grade is available from Fluka, catalog number 40234, www.sigma-aldrich.com.]
Lead Acetate, Pb(C2H3O2)2·3H2O379.33 [301-04-2]Use ACS reagent grade.
Lead Acetate Paper Immerse filter paper weighing about 80 g 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), PbO223.20 [1317-36-8]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 300 mg, freshly ignited in a muffle furnace at 600 ± 50, and dissolve it by warming with 10 mL of water and 1 mL of glacial acetic acid. Dilute with 75 mL of water, heat to boiling, add 50.0 mL of 0.1 N potassium dichromate VS, and boil for 2 to 3 minutes. Cool, transfer to a 200-mL volumetric flask with the aid of water, dilute with water to volume, mix, and allow to settle. Withdraw 100.0 mL of the clear liquid, and transfer to a glass-stoppered flask. Add 10 mL of diluted sulfuric acid and 1 g of potassium iodide, insert the stopper, mix gently, and allow to stand for 10 minutes. Then titrate the liberated iodine, representing the excess of dichromate, with 0.1 N sodium thiosulfate VS, adding 3 mL of starch TS as the endpoint is approached: each mL of 0.1 N potassium dichromate is equivalent to 7.440 mg of PbO. Not less than 98% is found.
Insoluble in acetic acid Dissolve 2 g in 30 mL of dilute glacial acetic acid (1 in 2), boil gently for 5 minutes, filter, wash the residue with diluted acetic acid, and dry at 105 for 2 hours: the residue weighs not more than 10 mg (0.5%).
Substances not precipitated by hydrogen sulfide Completely precipitate the lead from the filtrate obtained in the test for Insoluble in acetic acid by passing hydrogen sulfide into it, filter, and wash the precipitate with 20 mL of water. To one-half of the mixed filtrate and washings add 5 drops of sulfuric acid, evaporate to dryness, and ignite at 800 ± 25 for 15 minutes: the residue weighs not more than 5 mg (0.5%).
Volatile substances Accurately weigh about 5 g, and heat strongly in a covered porcelain crucible: it loses not more than 2.0% of its weight.
Lead Nitrate, Pb(NO3)2331.21 [10099-74-8]Use ACS reagent grade.
Lead Perchlorate, Pb(ClO4)2·3H2O460.15Use ACS reagent grade.
Lead Tetraacetate, C8H12O8Pb443.38 [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.
Melting range 741: between 175 and 180.
Linalool (3,7-Dimethyl-1,6-octadien-3-ol), C10H18O154.25 [78-70-6]Use a suitable grade.
Linoleic Acid, C18H32O2280.4 [60-33-3]Clear, colorless liquid. Use a suitable grade.
-Lipoic Acid, C8H14O2S2206.3 [1077-28-7]Yellow powder. Use a suitable grade.
Liquid Petrolatum Use Mineral Oil.
Lithium Chloride, LiCl42.39 [7447-41-8]Use ACS reagent grade.
Lithium Hydroxide, LiOH·H2O41.96 [1310-65-2]Use ACS reagent grade.
Lithium Metaborate, LiBO249.75 [13453-69-5]Use ACS reagent grade.
Lithium Nitrate, LiNO368.95 [7790-69-4]Colorless crystals. Use a suitable grade labeled to contain not less than 97.0%.
Lithium Perchlorate, LiClO4106.39 [7791-03-9]Use ACS reagent grade.
Lithium Sulfate, Li2SO4·H2O127.96 [10377-48-7]Use ACS reagent grade.
Lithocholic Acid, C24H40O3376.57 [434-13-9]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 110 for 20 minutes, and examined visually and under long-wavelength UV light, a single spot is exhibited.
Melting range 741 : between 184 and 186.
Litmus [1393-92-6]A blue pigment prepared from various species of Rocella DeCandolle, Lecanora Acharius, 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 A gum obtained from the ground endosperms of Ceratonia siliqua Linné Taub. (Fam. Leguminosae). Use Locust Bean Gum, FCC.
l-Lysine (2,6-Diaminohexanoic Acid), C6H14N2O2146.19 [56-87-1]Crystalline needles or hexagonal plates. Soluble in water; very slightly soluble in alcohol; insoluble in ether.
Specific rotation 781 : between +25.5 and +26.0.
Test solution: 20 mg per mL, in dilute hydrochloric acid (1 in 2).
Nitrogen content, Method I 461: between 18.88% and 19.44% of N is found, corresponding to not less than 98.5% of C6H14N2O2, the test specimen previously having been dried at 105 for 2 hours.