Na2SO4·10H2O 322.20

Sulfuric acid disodium salt,decahydrate.
Disodium sulfate decahydrate [7727-73-3].

Anhydrous 142.04 [7757-82-6].

Packaging and storage— Preserve in tight containers,preferably at a temperature not exceeding 30.

Labeling— Label it to indicate whether it is the decahydrate or is anhydrous.

Identification— Asolution (1in 20)responds to the tests for Sodium á191ñand for Sulfate á191ñ.

Acidity or alkalinity— To 10mLof a solution,containing the equivalent of 1.0g of Na2SO4·10H2Oin 20mLof water,add 1drop of bromothymol blue TS:not more than 0.50mLof either 0.010Nhydrochloric acid or 0.010Nsodium hydroxide is required to change the color of the solution.

Loss on drying á731ñ— Dry at 105for 4hours:the decahydrate loses between 51.0%and 57.0%of its weight,and the anhydrous form loses not more than 0.5%of its weight.

Chloride á221ñ— Aportion equivalent to 1.0g of Na2SO4·10H2Oshows no more chloride than corresponds to 0.30mLof 0.020Nhydrochloric acid (0.02%).

Heavy metals á231ñ— Dissolve a portion containing the equivalent of 2.0g of Na2SO4·10H2Oin 10mLof water,add 2mLof 0.1Nhydrochloric acid,then add water to make 25mL:the limit is 0.001%.

Assay— Weigh accurately a portion of Sodium Sulfate,equivalent to about 400mg of anhydrous sodium sulfate,dissolve in 200mLof water,and add 1mLof hydrochloric acid.Heat to boiling,and gradually add,in small portions and while constantly stirring,an excess of hot barium chloride TS(about 8mL).Heat the mixture on a steam bath for 1hour,collect the precipitate of barium sulfate on a tared filtering crucible,wash until free from chloride,dry,ignite,and weigh.The weight of the barium sulfate so obtained,multiplied by 0.6086,represents its equivalent of Na2SO4.

Expert Committee:(PA4)Pharmaceutical Analysis 4

USP28–NF23Page 1794

Phone Number:1-301-816-8251