ON THE TARTRATE OF IRON AND POTASSA. 
1S9 
precipitated from the solution in the state of a hydrate, by 
the addition of solution of potassa, and washed with pure 
water until deprived of adhering saline matter. This hydrate 
of the sesquioxide of iron is then boiled with bi-tartrate of 
potassa until it is dissolved; the solution, filtered and evaporated 
to dryness. If, after the solution of the hydrated oxide, the 
liquor is acid, solution of sesqui-carbonate of ammonia is 
directed to be added until it is neutral. 
The salt thus obtained has a dark olive green color, is very 
deliquescent, and when an attempt is made to dissolve it, an 
insoluble residue remains, which is most probably the proto- 
tartrate of iron. 
In repeating this process it has been found that more than 
a twenty-third of the bi-tartrate remains undissolved. Though 
at first deliquescent, this salt after standing three months be- 
came of a mottled, light green color, and was much less solu- 
ble than when first made,and had an ammoniacal odor. This is 
accounted for, by supposing the decomposition of the tartrate 
of ammonia, formed by the addition of the sesqui-carbonate of 
ammonia to neutralize the acidity of the solution. Its insolu- 
bility is doubtless due to the conversion of the per-tartrate of 
iron into a joro/fo-tartrate by anew arrangement of its con- 
stituents, a change, which, according to Soubeiran and Capi- 
-taine, it is liable to undergo. This preparation, according to 
Phillips, has the following composition, viz.: 
\ an atom sesqui-oxide of Iron 40= IS. 18 
1 " Potassa, . . 47=21.36 
2 « Tartaric acid, 133 = 60.46 
1 " Tart, of Iron and Potassa, 220 100.00. 
Hence the oxygen in the oxide of iron is to that in the potassa 
as 1.5 to 1. 
In a paper published originally in the Jour, de Pharm., 
and republished in the April number of this volume, by 
Soubeiran and Capitaine, the outline of a process is given 
for the preparation of tartrate of iron and potassa in a way 
