Dr. Kane on the Compounds of the Oil of Peppermint, 419 
indeed pretty broadly, although without having analysed the 
liquid oil, which he might so readily have done, that the for- 
mula of Blanche! is the true one, and that mine, in as far as 
it differs from it, is likely to be incorrect. His words are : 
“ Si I’essence de menthe poivree liquide presente la meme 
composition que I’essence de menthe concrete, ce qui est tres 
probable d’apres les observations de M. Robert Kane, qui 
est conduit cependant, quoique le rapport numerique qu’il a 
trouve, soit le meme, a adopter une formule different de celle 
que je viens de presenter, formule du reste qui n’est deduite 
ni de la densite de la vapeur, ni d’aucune combinaison dans 
lequelle Fessence de menthe rentrerait,” &c. Now I purpose 
to show in this notice that Mr. Walter has not done justice 
to his own analyses; for that by giving them their just inter- 
pretation, he would have found BlancheFs formula to be in- 
exact, and that the stearopten possesses the precise constitu- 
tion which I have assigned for the oil. 
In an organic analysis the sources of error act in opposite 
directions on the carbon and on the hydrogen ; there cannot 
be more carbon obtained than was present in the substance ; 
and from the facility with which the hydrogen is burned, 
there is never less water obtained. In practice, a chemist 
very seldom succeeds in a complete combustion of the carbon ; 
and almost in all cases, from the hygrometric nature of his 
materials, he gets more water than he ought. Hence in de- 
ducing a formula from a set of analyses, the highest number 
obtained for the carbon, and the lowest number obtained for 
the hydrogen, are those most likely to be true, and are those 
on which the formula should be constructed. There may be 
cases in which water may be lost, but it must arise either from 
an error in weighing or from bad management in the analysis. 
Setting out from these principles I will proceed to discuss 
Mr. Walter’s numerical results. 
In six analyses of the solid oil, the highest value he ob- 
tained for the carbon was 77*6S, and the mean of five results 
was 77*36. The lowest result for hydrogen was 12*52 and 
the mean of four was 12*66. Mr. Walter’s analyses and 
theory are therefore, — 
Carbon 
Analysis. 
77*68 
Analysis. 
77*36 
C.0 
Theory. 
77*27 
Hydrogen . . 
12*52 
12*66 
H.0 
12*62 
Oxygen . ... 
9*80 
9*98 
O 
10*11 
100*00 
100*00 
100*00 
It is also quite evident that the results of Mr. Walter’s 
analyses cannot be considered as exceedingly correct, when 
