of the French Chemists. 89 



the latter rests, or that the true formula for the oil is that al- 

 ready assigned. 



These experiments were made in the winter of 1839, and 

 at the time I had concluded them I was under the impression 

 that the oil, to which they relate, was a new substance, or 

 rather one which had not been previously described. In some 

 time after, however, upon looking over the second part of 

 Mr. Graham's Elements of Chemistry, which had been sent 

 me by the author, I was much surprised at rinding at page 

 134, in a table of the volumes of atoms in the gaseous state, 

 mention made of a substance under the designation of " oil 

 of the ardent spirit from potatoes," to which he attributed 

 the very same formula and density of vapour which I had 

 found to belong to the oil found in grain-whisky, in the ex- 

 amination of which I had been recently engaged. 



Anxious to investigate the matter further, and to ascertain 

 if the two oils were certainly the same, I looked into Ber- 

 zelius's System, and the 5th volume of the Traite Je Chimie, 

 appliquee aux Arts, by Dumas, devoted to the subject of or- 

 ganic chemistry, but could not find any mention in either of 

 the essential oil from potatoe spirit alluded to by Graham. 

 Upon, however, turning to Dr. Thomson's recent volume on 

 vegetable chemistry, I found, page 481, a notice of this fluid s 

 and references to the 30th and 56th volumes of the Annales de 

 Chim. etdeP/tysAn the former of which its origin and properties 

 are described by Pelletier,and in the latter of which its analysis 

 is detailed by M. Dumas. The properties I find ascribed by 

 these chemists to the potatoe spirit oil are precisely those which 

 belong to that which I have examined from corn-whisky, the 

 only difference being that Pelletier represents its specific gra- 

 vity as '821, whereas I have found that of the oil I obtained 

 from Mr. Scanlan but '813, a difference, however, easily ex- 

 plained by the circumstance of his not having taken the ne- 

 cessary steps for rendering the fluid he examined perfectly 

 free from water and alcohol. The analytic results also of 

 M. Dumas are nearly identical with mine, approaching how- 

 ever more nearly, as might indeed be expected from his great 

 skill in this department of chemistry, to the formula C 5 H 6 O t 

 which he adopts, and which Professor Graham has taken from 

 his memoir. I may lastly mention, as a very unusual coinci- 

 dence, that the specific gravity of its vapour, as obtained by 

 Dumas, is 3*147, or but unity in the second place of decimals 

 greater than what has resulted for the corn-spirit oil from my 

 experiments. 



We thus arrive at the conclusion, that the two fluids are 

 identical, or that the oil which has hitherto been considered 



