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

Litmus Paper, Blue
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Litmus Paper, Blue Boil 10 parts of coarsely powdered litmus under a reflux condenser for 1 hour with 100 parts of ethanol (96%), decant the ethanol and discard. To the residue add 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 extract and allow to dry.

Complies with the following test.

Sensitivity Immerse a strip (60  mm  ×  10  mm) in 100  ml of 0.002m hydrochloric acid. On shaking, the paper turns red within 45 seconds.