408 
in the hydrogen, though trifling in amount, being upon the 
opposite side to that on which it usually occurs, it became 
expedient to resort to some method of verification. The 
specific gravity of the vapour of the oil was therefore taken 
by the well known method of Dumas, and found to be 3.137: 
the formula c,;H;0 would make it 3.072. But there is 
here so close a correspondence between experiment and 
calculation, that no doubt can remain as to the correctness 
of the basis on which the latter rests, or that the formula 
already arrived at represents correctly the constitution of the 
oil. 
These experiments were made in the winter of 1839, and 
Dr. Apjohn stated that he was then under the impression 
that the oil in question was a new substance, or rather one 
which had not been previously described. Some months 
after, however, upon looking over the second part of Pro- 
fessor Graham’s Elements of Chemistry, he was surprised 
to find (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 spirits from potatoes,” to which was 
attributed the very same formula, and density of vapour, 
which he had found to belong to the oil of corn whiskey, 
given him by Mr. Scanlan. Anxious to investigate the 
matter further, and to ascertain whether the two oils were cer- 
tainly the same, Dr. Apjohn looked into Dr. Thomson’s fifth 
volume on Organic Chemistry, and found there (page 481) 
a notice of the potato oil, with a reference to the 30th and 
56th volumes of the Annales de Chimie, in the former of 
which its origin and properties are described by Pelletan, 
and in the latter of which its analysis is given by Dumas. 
Upon perusing these papers, his suspicions as to the identity 
of the two oils were confirmed. In composition and proper- 
ties they are the same; the only difference being, that Pelletan 
represents the potato oil as having the specific gravity .821, 
whereas Dr. Apjohn found that of the corn oil but .813,—a 
