409 



difference, however, easily explained by the circumstance of 

 the former chemist not having taken the necessary steps for 

 purifying perfectly the liquid he examined. 



As a very unusual coincidence it may be observed, that 

 the specific gravity of the vapour of potato oil, as obtained 

 by Dumas, is 3.147, or but unity in the second place of deci- 

 mals greater than has resulted for the corn spirit oil from Dr. 

 Apjohn's experiments. The oil therefore of Pelletan and 

 Dumas is not, as is generally supposed, peculiar to potato 

 spirit, but occurs also in that developed by the fermentation 

 of the cerealia. From this latter source also it admits of 

 being obtained in great quantity. When first observed by 

 Mr. Coffey at Sir Fehx Booth's, there was an inch of it in 

 the faint receiver ; and from the diameter of this vessel he 

 estimated its total amount to be at least fifty gallons. This 

 is the quantity produced at that establishment every fort- 

 night, the excise laws compelling the distiller to distil and 

 brew alternately, and about a week being consumed in each 

 process. 



The whiskey manufactured some years ago contained. 

 Dr. Apjohn observed, a considerable quantity of this oil, and 

 owed to its presence a great deal of the pungency of taste 

 and smell by which it was distinguished. From the nature 

 of the still at present generally used, but a small por- 

 tion of this substance passes over ; and hence the reason why 

 the spirit now made is, as compared with the product 

 of the old processes, less disagreeable to the palate, and pro- 

 bably less injurious to the constitution. It is undoubtedly 

 owing to the same cause, (an improvement in the process 

 of distillation,) that this oil has at length been noticed in the 

 distillers' faints. Upon the old system of manufacture the 

 greater portion of it was driven over, and was held dissolved 

 by the spirit into which it was thus introduced ; but with the 

 modern stills, particularly that devised by Mr. Coffey, no- 

 thing having so high a boiling point as this oil, can by pos- 



