386 Dr. pRouT on the ultimate composition 
This composition has been approached very nearly by 
several chemists; but no one, so far as I know, has given 
it exactly. 
Tartaric acid in crystals is composed of 
Carbon 32-0 
Water 36-0 
Oxygen 32-0, 
a composition assigned to it by Dr. Thomson in his work 
just quoted. 
Malic acid. I am not acquainted with any analysis of malic 
acid except that of M. Vauquelin,* which has not, I believe, 
obtained much confidence among chemists, chiefly on account 
of the large proportion of hydrogen which he assigns to it. 
The acid I employed was obtained from the berries of the 
mountain ash by a process very similar to that of Mr. 
Donovan. It was not analyzed per se, but in combination 
with lead, with lime, and with copper, and was found, ab¬ 
stracting water not essential to its composition, to consist of 
Carbon 40*68 
Water 45*76 
Oxygen 13*56, 
This acid, in many points of view, may be regarded as 
one of the most interesting and important of all the vegetable 
acids. 
Saclactic acid. The unexpected composition of this acid in¬ 
duced me to investigate its properties more fully than I had 
otherwise intended. What I first employed was obtained 
from the sugar of milk, and hence was tolerably pure, though 
not perhaps completely so. Latterly, I have preferred that 
* Annales de Chimie et de Physique, vi. 337. 
