TRANSACTIONS OF THE SECTIONS. 47 



On tlie Existence of Putrescible Matter in Jtiver and Lake Waters. 

 By J. Alfeed Wanklyn-. 



Action of Sodium on Valerianic and similar Ethers. 

 By J. Alfeed "Wanextit. 



On the Electrical Besisfances of the Fixed and Volatile Oils*, 

 By T. T. P. Beuce Waeeen. 



The -want of an aclmowledged and reliable means of recog-nizina: the purity or 

 condition of sranples of oils has long been felt by pharmaceutists. No tests, or 

 system of tests at present used, are free from objection. An inspection of the optical 

 characters of the oils, -whether fixed or volatile, will be sufficient to confirm the 

 truth of this observation. 



The polariscope has at best a very lunited scope of application, whilst the deter- 

 mination of the refractive or dispersive qualities requires such precise adjustments 

 that the suitability either of the one or the other for the pm-poses of a technical 

 test maj' be fairly questioned. The refractive power of the oils, both fixed and 

 volatile, has so small a variation, that the difierence produced on the refractive 

 power of cany oil by the addition of a small quantity of another, would be barely 

 perceptible. The objection ag-aiust the measm'ement of the dispersive action as a 

 means of expressing- the value of an oil is, that the determination of the difterences 

 of indices of refraction for the extreme rays is at once tedious and unreliable ; the 

 scale of dispersions offers, however, a much wider range of difterences. 



It is probable that the compai'ison of two samples of oil by the irrationalities of 

 their dispersion is worthy of some attention. The author is not aware of its being 

 applied as a test ; but the samples could stand side by side with respect to the 

 illuminating source, and their spectra projected side by side could be easily observed 

 and compared. 



Although bromine and iodine exert on some of the essential oils chemically 

 characteristic effects, it does not appear certain to what extent the action may be 

 modified by the addition of small quantities of other oils ; consequently the che- 

 mical phenomena, as well as a knowledge of their specific gi-avities and boiling- 

 points, cannot be considered as ofl'ering any assistance to the detection of accidental 

 or intentional impurities when existing in small quantities. 



The process which the author submitted is one which has given great satis- 

 faction in all the experiments which he has made, and was suggested b}' a discoveiy 

 due to M. Rousseau, quoted by l)e la Rive, " that olive-oil, when mixed with y5o 

 part its volmne of oil of poppies, increased the number of vibrations of a magnetic 

 needle in a given time, when the same was included or made to form part of a 

 voltaic circuit." This isolated fact would be of service for the determination of 

 the purity of olive-oil, if oil of poppies were the only soiDhisticatiaig ingredient, 



The.aclulterants of the volatile oils are principally turpentine and alcohol f. 



Compared with any of the essential oils, turpentine has an immense resistance, 

 whilst that of alcohol is enormously lower than any of them, except perhaps that 

 of oil of bitter almonds, whicli is so low that he did not measure it. 



The importance of this general fact is at once apparent, since the addition either 

 of alcohol or turpentine in the smallest quantity is readily detected ; and the quan- 

 tity denoted by the vaiiation in the defiection, either when compared with a standard 

 of Irno-mi purit}', or by the resistances themselves. 



The oils of lemon and bcrgamot, when mixed with a small proportion of tur- 

 pentine, do not, however, show such marked differences as the generality of the 

 essential oils. 



The addition of turpentine to oil of lavender is more strongly marked by this test 

 than in any other case. 



The effects produced by mixing different specimens of the same oil together are 



* Published in c.rfcnso in the ' Chemic.nl Nev.-s' for Sept. 20, 18G7. 

 t The foreign oils are no doubt sometimes entirely substituted for the English oils, or 

 Inrgely diluted with them, 



