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	The Pharmaceutical Journal Vol 270 No 7238 p301 1 March 2003	This page Reprint Photocopy
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Chloroform water

Attention to detail essential

From Mr D. A. Canniford, MRPharmS

I write regarding the pharmacy information pointers on the preparation of chloroform and peppermint water (PJ, 1 February, p172). When I did my training, well over 50 years ago, it was stressed heavily that attention to detail and as high a degree of accuracy as possible was essential to help to prevent errors (which is why this article was written). I was taught that if you added 39 parts of purified water to 1 part of concentrated chloroform water (BPC) you did not get 40 parts because the solution of the alcohol in water caused a contraction in total volume and therefore you must dilute 1 part with sufficient water to make 40 parts.

Furthermore chloroform water prepared from concentrated chloroform water will have a residual ethanol content of about 1.35 per cent, not 1.5 per cent as stated (the concentrate only contains 90 per cent ethanol, not 100 per cent).

Dennis Canniford
Tullow, Ireland

Dr COLIN CABLE, Royal Pharmaceutical Society fellow in pharmaceutics, replies:

Much of the information given in the pharmacy information pointers article regarding the preparation and ethanol content of chloroform water and peppermint water through dilution of the respective concentrated water was based on guidance provided in the general monograph for Aromatic Waters in the British Pharmaceutical Codex (BPC).

Strictly speaking, to give an accurate final volume, one part of a concentrated aromatic water should be diluted up to 40 parts with water. However, in practical terms, if diluted as recommended in the BPC (ie, 1 part diluted with 39 parts water), the contraction in volume will be of the order of 0.2 ml for each 100 ml prepared.

In terms of the residual ethanol content of chloroform water and peppermint water produced by dilution of the concentrated water, as correctly indicated in the letter, this should have been described as "about 1.5 per cent of ethanol (90 per cent)".

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