Packaging and storage—
Preserve in well-closed containers.
Labeling—
The quantity of dibasic calcium phosphate stated in the labeling is in terms of CaHPO4·2H2O.
Identification—
A:
Afiltered portion of the solution prepared for the
Assayresponds to the tests for
Calcium á191ñ.
B:
Afiltered portion of the solution prepared for the
Assay,neutralized with ammonium hydroxide,responds to the tests for
Phosphate á191ñ.
Dissolution á711ñ—
Medium:
0.1Nhydrochloric acid,900mL.
Apparatus 2:
75rpm.
Time:
45minutes.
Procedure—
Determine the amount of CaHPO4·2H2Odissolved,employing atomic absorption spectrophotometry at a wavelength of about 422.7nm in filtered portions of the solution under test,suitably diluted with Dissolution Mediumif necessary,in comparison with a Standard solution having a known concentration of calcium in the same medium.
Tolerances—
Not less than 75%(Q)of the labeled amount of CaHPO4·2H2Ois dissolved in 45minutes.
Assay—
Weigh and finely powder not less than 20Tablets.Weigh accurately a portion of the powder,equivalent to about 1g of dibasic calcium phosphate (dihydrate),and transfer to a 100-mLvolumetric flask containing 15mLof hydrochloric acid and 10mLof water.Heat on a steam bath,with occasional mixing to dissolve the dibasic calcium phosphate,but not longer than 30minutes.Cool,add water to volume,and mix.If the preparation is not clear,filter,discarding the first 10mLof the filtrate (reserve portions of the solution for the
Identificationtests).Transfer 25.0mLof the solution to a 250-mLbeaker equipped with a magnetic stirrer.Proceed as directed in the
Assayunder
Dibasic Calcium Phosphate,beginning with “With constant stirring.”Each mLof 0.05
Medetate disodium is equivalent to 8.604mg of CaHPO
4·2H
2O.