Ca(OH)2 74.09

Calcium hydroxide.
Calcium hydroxide [1305-62-0].

Packaging and storage— Preserve in tight containers.

Identification—

Limit of acid-insoluble substances— Dissolve 2.0g in 30mLof 4Nhydrochloric acid,and heat to boiling.Filter the mixture,wash the residue with hot water,and ignite:the weight of the residue does not exceed 10mg (0.5%).

Carbonate— Mix 2g with 50mLof water:the addition of an excess of 3Nhydrochloric acid to the mixture does not cause more than a slight effervescence.

Heavy metals á231ñ— Dissolve 2.0g in 20mLof 3Nhydrochloric acid,and evaporate on a steam bath to dryness.Dissolve the residue in 20mLof water,and filter.Dilute the filtrate with water to 40mL,and to 20mLof the resulting solution add 1mLof 0.1Nhydrochloric acid,then add water to make 25mL:the limit is 20µg per g.

Limit of magnesium and alkali salts— Dissolve 0.50g in a mixture of 30mLof water and 10mLof 3Nhydrochloric acid,and proceed as directed in the test for Magnesium and alkali saltsunder Calcium Carbonate,beginning with “heat the solution,and boil for 1minute.”The weight of the residue does not exceed 12mg (4.8%).

Organic volatile impurities,Method IVá467ñ: meets the requirements.

Assay— Transfer about 1.5g of Calcium Hydroxide,accurately weighed,to a beaker,and gradually add 30mLof 3Nhydrochloric acid.When the solution is dissolved,transfer it to a 500-mLvolumetric flask,rinse the beaker thoroughly,adding the rinsings to the flask,dilute with water to volume,and mix.Pipet 50mLof the solution into a suitable container,add 100mLof water,15mLof 1Nsodium hydroxide,and 300mg of hydroxy naphthol blue,and titrate with 0.05Medetate disodium VSto a blue endpoint.Each mLof 0.05Medetate disodium is equivalent to 3.705mg of Ca(OH)2.

Expert Committee:(PA6)Pharmaceutical Analysis 6

USP28–NF23Page 328

Phone Number:1-301-816-8389