383 
of simple alimentary substances , &c. 
that the hydrogen and oxygen exist in it in the proportions in 
which they form water. Some experiments which I made many 
years ago appeared to render this probable, but from the 
difficulties attending the analysis of this acid, and the uncer- 
tainty arising from the properties of the oxide copper for- 
merly stated, I was unable to satisfy myself completely on 
the subject. On repeatedly burning, however, a very fine 
specimen of the acetate of copper, in a given bulk of oxygen 
gas, with the apparatus described at the commencement of 
this Paper, it was found that the volume of the gas underwent 
no change, and hence, that the above opinion was correct. 
Acetic acid, freed from non-essential water, I find to be 
composed of Carbon 47*05 
Water 52*95, 
results which almost exactly agree with those of other 
chemists. 
Sugar of Milk . 
The sugar of milk employed in these experiments was 
prepared by myself in the usual manner, and rendered as 
pure as possible by repeated crystallizations. It was then 
freed from its hygrometric moisture by confinement under 
a receiver with sulphuric acid, and was found to consist of 
Carbon 40 
Water 60, 
results almost exactly agreeing with those of Berzelius. 
of organic nature are combined, assigns to vinegar this composition. See Annals 
of Philosophy, v. 174 (O. S.) Dr. Thomson also, in the last edition of his Che- 
mistry, gives the same composition ; though in his more recent work he has 
assigned to it another proportion of hydrogen. 
