On the use of alcohol as a test for the purity of croton oil / by Robert Warington.

  • Warington, Robert, 1807-1867.
Date:
1865
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Licence: Public Domain Mark

Credit: On the use of alcohol as a test for the purity of croton oil / by Robert Warington. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    [Reprinted from the Pharmaceutical Journal, for January, 1865.] ON THE USE OF ALCOHOL AS A TEST FOR THE PURITY OF CROTON OIL. BY ROBERT WARINGTON, F.R.S., F.C.S. The College of Physicians of Edinburgh in their Pharmacopoeia of 1839, under the article “ Croton Oil,” contained in the Materia Medica, gave the following directions for testing its purity :—“ When agitated with its own vo- lume of pure alcohol and gently heated, it separates on standing, without hav- ing undergone any apparent diminution.” The alcohol is ordered to be prepared from rectified spirit by well-burnt lime, and the density should not exceed *796. This test has been transcribed vet-batim into various works on Materia Medica, dispensatories, etc., and is repeated in the Pharmaceutical Journal for July, 1814, vol. iv. p. 47, and December, 1849, vol. ix. p. 296, in answer to correspondents. In the latter volume, however, at a later date, May, 1850, vol. ix. p. 499, a very valuable paper, by the late Dr. Pereira, was published on the subject, enti- tled, “ On the Alcohol Test of the Purity of Castor and Croton Oils, by Jona- than Pereira, M.D., F.R.S.” As it is only with the experiments and deductions concerning croton oil that we have to deal, I shall only allude to those parts of the paper which relate to it, and that as briefly as the nature of the subject will admit. “ Experiment 2.—Eight volumes of pale or amber-coloured East India croton oil were mixed with eight volumes of alcohol, specific gravity -796, and gently heated. In two days a separation had taken place, the oil now measured 8f volumes, while the alcohol measured only 1\ volumes (or 10 volumes oil -f 10 vo- lumes alcohol = 1094 oil 9'06 alcohol). In this case the croton oil had taken up three-quarters of a volume of alcoholDr. Pereira considers that these fluids exert a mutual solvent action on each other, similar to that of ether and water. This mutual action, however, he states, “ is not uniform, but varies with the samples of oil. At first,” he says, “ I was inclined to ascribe this varia- tion to differences of purity in the several samples of oil examined, but I am now convinced this is not the case, and that they depend on other circum- stances.” ‘‘ Experiment 6.—One volume of dark-coloured English-expressed croton oil was mixed with one volume of alcohol, sp. gr. -796, by shaking, without any additional heat, a uniform transparent mixture was obtained; and no sepa- ration took place on standing for several weeks.” Upon which Dr. Pereira naturally asks, “On what does this difference depend? Does it arise from