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

Litmus Paper, Blue
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Litmus Paper, Blue Boil 10 parts of coarsely powdered litmus for 1 hour with 100 parts of ethanol (96%). Decant the alcohol and add to the residue a mixture of 45 parts of ethanol (96%) and 55 parts of water. After 2 days decant the clear liquid. Impregnate strips of filter paper with the solution and allow to dry.

Test for sensitivity Immerse a strip measuring 10 mm by 60 mm in a mixture of 10 mL of 0.02 M hydrochloric acid and 90 mL of water. On shaking the paper turns red within 45 seconds.