THE STUDY OF TARTARIC ACID. 
33 
ART. VII. — OBSERVATIONS TOWARDS THE STUDY OF TAR- 
TARIC ACID. By MM. E. Soubeiran and H. Capitaine. 
The curious observation of Dumas and Liebig, of the pro- 
perty possessed by tartar emetic, of losing, when exposed to 
an elevated temperature, two equivalents of water more than 
is lost by the other tartrates, gives some importance to ex- 
periments made with a view of ascertaining whether the same 
character appertained to the other tartrates having a similarity 
in composition. It might be expected to receive from these 
some light as to the real composition of tartaric acid, which 
the principal experiments of the two experienced chemists 
have left totally in doubt. 
Tartrate of Iron and Potassa. 
Our first attempts were made with the tartrate of iron and 
potassa, a salt but little understood at present, and whose che- 
mical history is not without interest. We are acquainted 
with only one analysis of the double tartrate of sesquioxide of 
iron and potassa, that of Mr. Philips, who found that two 
atoms of tartaric acid were united with one atom of potassa, 
and one-half an atom of sesquioxide of iron; and that the 
oxygen of this latter was to that of the potassa as 1.5 to 1. 
From our experiments it will be seen that Mr. Philips em- 
ployed a salt which was not saturated with the sesquioxide of 
iron. 
To prepare the tartrate of iron and potassa, pure bitartrate 
of potassa, and equally pure hydrated sesquioxide of iron, 
must be mixed together in water, and digested at the tempera- 
ture of 50° to 60° c, for twenty-four to thirty-six hours, shak- 
ing the mixture occasionally; the excess of hydrate is then to 
be separated by the filter,, and the liquor evaporated to dry- 
ness by a low heat. A salt will then be obtained under the 
form of brilliant scales, of a brown or nearly black color, but 
of a ruby red, when placed between the eye and the light. 
To analyse this salt, after it had been pulverized and dried 
VOL. VI. — NO. i, 5 
