MnCl2·4H2O 197.90

Manganese chloride (MnCl2)tetrahydrate.
Manganese (2+)chloride tetrahydrate [13446-34-9].

Anhydrous 125.84 [7773-01-5].

Packaging and storage— Preserve in tight containers.

Identification—

pHá791ñ: between 3.5and 6.0,10g dissolved in 200mLof carbon dioxide-and ammonia-free water being used.

Loss on drying á731ñ— Dry it at 50for 2hours,then raise the temperature to 150for 24hours:it loses between 36.0%and 38.5%of its weight.

Insoluble matter— Transfer 10g to a 250-mLbeaker,add 150mLof water,cover the beaker,and heat to boiling.Digest the hot solution on a steam bath for 1hour,and pass through a tared,fine-porosity filtering crucible.Rinse the beaker with hot water,passing the rinsings through the filter,and finally wash the filter with additional hot water.Dry the filter at 105:the residue weighs not more than 0.5mg (0.005%).

Sulfate á221ñ— A2.0g portion shows no more sulfate than corresponds to 0.10mLof 0.020Nsulfuric acid (0.005%).

Substances not precipitated by ammonium sulfide— Dissolve 2.0g in about 90mLof water,add 5mLof ammonium hydroxide,and warm the solution to about 80.Pass a stream of hydrogen sulfide through the solution for 30minutes.Dilute with water to 100mL,mix,and allow the precipitate to settle.Decant the supernatant through a fine-porosity filter,and transfer 50.0mLto an evaporating dish that previously has been ignited and tared.Evaporate the filtrate to dryness,cool,add 0.5mLof sulfuric acid,heat gently to remove the excess acid,and ignite at 800±25for 15minutes:the weight of the residue is not greater than 2.0mg (0.2%as sulfate).

Iron á241ñ— Dissolve 2.0g in 40mLof water:the limit is 5µg per g.

Zinc— Dissolve 1g in a mixture of 48mLof water and 2mLof sulfuric acid,and add,slowly and with constant agitation,1mLof potassium ferrocyanide solution (1in 100):no turbidity is produced within 5minutes.

Heavy metals,Method Iá231ñ— Dissolve 6.0g in 30mLof water.Use 25mLof this solution in the Test Preparation,and use the remaining 5.0mLin preparing the Standard Preparation:the limit is 5µg per g.

Organic volatile impurities,Method Iá467ñ: meets the requirements.

Assay— Transfer about 425mg of Manganese Chloride,accurately weighed,to a 400-mLbeaker,dissolve in about 25mLof water,add 300mg of ammonium chloride and 0.5g of hydroxylamine hydrochloride,and swirl to dissolve.Warm slightly on a hot plate,and dilute with water to 100mL.Add about 3mLof triethanolamine,stir the solution,using,preferably,a magnetic stirrer,begin the titration by adding about 25mLof 0.05Medetate disodium VS,using a suitable buret,then add 10mLof ammonia–ammonium chloride buffer TS,and 1mLof eriochrome black TS,and complete the titration with 0.05Medetate disodium VSto a blue endpoint.Each mLof 0.05Medetate disodium is equivalent to 6.292mg of MnCl2.

Expert Committee:(PA1)Pharmaceutical Analysis 1

USP28–NF23Page 1180

Phone Number:1-301-816-8379