• British Pharmacopoeia Volume V
  • Appendices
  • Appendix I A. General Reagents

Silica Gel G
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Silica Gel G (112926-00-8)

Contains about 13% of calcium sulfate hemihydrate.

Fine, white or almost white, homogeneous powder with a particle size of about 15 μm.

Calcium sulfate content Place 0.25 g in a ground-glass stoppered flask, add 3 mL of dilute hydrochloric acid and 100 mL of water and shake vigorously for 30 minutes. Filter through a sintered-glass filter (2.1.2) and wash the residue. Carry out on the combined filtrate and washings the complexometric assay of calcium (2.5.11).

1 mL of 0.1 M sodium edetate is equivalent to 14.51 mg of CaSO4,½H2O.

pH (2.2.3) Shake 1 g for 5 minutes with 10 mL of carbon dioxide-free water. The pH of the suspension is about 7.