276 ON THE TARTRATE OP IRON AND AMMONIA. 
equivalent of sesqui-carbonate of ammonia. The reaction is 
such, that the two equivalents of ammonia in the sesqui-car- 
bonate, combine with the four equivalents of tartaric acid, 
forming two equivalents of bicarbonate of ammonia, while 
three equivalents of carbonic acid and a portion of the water 
of the tartaric acid is set at liberty. Like the bitartrates of 
the other alkalies, this salt is but slightly soluble in cold wa- 
ter; and it comports itself, when mixed with sesqui-oxide of 
iron, in a manner similar to cream of tartar. 
Take of tartaric acid 100 drachms- 
Sesqui-carbonate of ammonia (crystalline) 39§ * 
Sesqui-oxide of iron 53| " 
Hydrochloric acid 180 " 
Solution of ammonia and water, of each a sufficient quan- 
tity. 
Dissolve the tartaric acid in a gallon of the water, and add 
the carbonate of ammonia gradually. A considerable quantity 
of a white crystalline powder subsides, which is bitartrate of 
ammonia, and with which the supernatant liquid is saturated. 
Dissolve the sesqui-oxide (precipitated carbonate U. S. P.) 
of iron in the hydrochloric acid, by means of a gentle heat, 
dilute the solution with six pints of water, and add a sufficient 
quantity of solution of ammonia to precipitate the sesqui- 
oxide. Separate this on a flannel filter, wash it with water 
until the washings pass tasteless, and add it to the solution 
containing the bitartrate of ammonia; then apply a gentle heat, 
by means of a water bath, until the whole of the sesqui-oxide 
of iron is dissolved, and a deep reddish-brown solution results. 
The solution thus obtained should be evaporated, by means of 
a water bath, to dryness. It is of importance to the ex- 
cellence of the product, that a moderate heat be employed, 
and that of a water bath is the best and most easily regu- 
lated. 
It will be observed that the carbonate of ammonia is di- 
rected to be in a crystalline form, because, when it has fallen 
into powder, or lost its transparency, it has become more or 
