Calcium Hydroxide Topical Solution
» Calcium Hydroxide Topical Solution is a solution containing, in each 100 mL, not less than 140 mg of calcium hydroxide [Ca(OH)2].
Prepare Calcium Hydroxide Topical Solution as follows (see Pharmaceutical Compounding—Nonsterile Preparations 795):
Calcium Hydroxide 3 g
Purified Water 1000 mL
Add the Calcium Hydroxide to 1000 mL of cool Purified Water, and agitate the mixture vigorously and repeatedly during 1 hour. Allow the excess calcium hydroxide to settle. Dispense only the clear supernatant.
[note—The solubility of calcium hydroxide, which varies with the temperature at which the solution is stored, is about 170 mg per 100 mL at 15 and less at a higher temperature. The official concentration is based upon a temperature of 25. ]
The undissolved portion of the mixture is not suitable for preparing additional quantities of Calcium Hydroxide Topical Solution.
Packaging and storage— Preserve in well-filled, tight containers, at a temperature not exceeding 25.
A: It absorbs carbon dioxide from the air, a film of calcium carbonate forming on the surface of the liquid.
B: When heated, it becomes turbid, owing to the separation of calcium hydroxide.
C: It responds to the tests for Calcium 191.
Alkalies and their carbonates— A portion of it, saturated with carbon dioxide and subsequently boiled, is neutral in reaction.
Assay— Pipet 100 mL of Topical Solution into a suitable container, add 50 mL of water, 15 mL of 1 N sodium hydroxide, and 300 mg of hydroxy naphthol blue, and titrate with 0.05 M edetate disodium VS to a blue endpoint. Each mL of 0.05 M edetate disodium is equivalent to 3.705 mg of calcium hydroxide [Ca(OH)2].
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Feiwen Mao, M.S.
Senior Scientific Liaison
(SM32010) Monographs - Small Molecules 3
USP35–NF30 Page 2457
Pharmacopeial Forum: Volume No. 27(6) Page 3259