Magnesium Chloride
MgCl2·6H2O 203.30

Magnesium chloride, hexahydrate
Magnesium chloride hexahydrate [7791-18-6].

Anhydrous 95.21 [7786-30-3].
» Magnesium Chloride contains not less than 98.0 percent and not more than 101.0 percent of MgCl2·6H2O.
Packaging and storage— Preserve in tight containers.
Labeling— Where Magnesium Chloride is intended for use in hemodialysis, it is so labeled.
Identification— A solution (1 in 20) responds to the tests for Magnesium 191 and for Chloride 191. [note—When performing the test for Chloride, acidify the sample solution with diluted nitric acid prior to adding 6 N ammonium hydroxide.]
pH 791: between 4.5 and 7.0, in a 1 in 20 solution in carbon dioxide-free water.
Insoluble matter— Dissolve 20 g, accurately weighed, in 200 mL of water, heat to boiling, and digest in a covered beaker on a steam bath for 1 hour. Filter through a tared filtering crucible, wash thoroughly, dry at 115, and determine the weight of the residue: not more than 0.005% is found.
Sulfate 221 A 10-g portion shows no more sulfate than corresponds to 0.50 mL of 0.020 N sulfuric acid (0.005%).
Barium— Dissolve 1 g in 10 mL of water, and add 1 mL of 2 N sulfuric acid: no turbidity is produced within 2 hours.
Limit of calcium—
Dilute hydrochloric acid, Lanthanum solution, Standard preparations, and Blank solution— Proceed as directed in the test for Limit of calcium under Magnesium Carbonate.
Test preparation— Transfer 10.0 g of Magnesium Chloride to a 200-mL volumetric flask, add water to dissolve it, add 4 mL of Lanthanum solution, dilute with water to volume, and mix.
Procedure— Proceed as directed for Procedure in the test for Limit of calcium under Magnesium Carbonate. Determine the concentration, C, in µg per mL, of calcium in the Test preparation using the calibration graph. Calculate the content of calcium, in percentage, in the portion of Magnesium Chloride taken by the formula:
in which C is as defined above; the multiplier of 0.001 is for conversion of µg per mL to mg per mL; V is the volume, in mL, of the Test preparation; and W is the amount of Magnesium Chloride, in mg, taken to prepare the Test preparation: the limit is 0.01%.
Potassium— Dissolve 5 g in 5 mL of water, and add 0.2 mL of sodium bitartrate TS: no turbidity is produced within 5 minutes.
Aluminum 206 (where it is labeled as intended for use in hemodialysis)— Proceed as directed, using 2.0 g of Magnesium Chloride to prepare the Test Preparation: the limit is 1 µg per g.
Heavy metals 231 Dissolve 2 g in water to make 25 mL: the limit is 0.001%.
Assay— Accurately weigh about 450 mg of Magnesium Chloride, dissolve in 25 mL of water, add 5 mL of ammonia–ammonium chloride buffer TS and 0.1 mL of eriochrome black TS, and titrate with 0.05 M edetate disodium VS to a blue endpoint. Each mL of 0.05 M disodium edetate is equivalent to 10.17 mg of MgCl2·6H2O.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Elena Gonikberg, Ph.D.
Senior Scientist
(MDGRE05) Monograph Development-Gastrointestinal Renal and Endocrine
USP32–NF27 Page 2831
Pharmacopeial Forum: Volume No. 32(6) Page 1720
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.