190 ON THE TARTRATE OF IRON AND POTASSA. 
that the product contains a much larger quantity of iron than 
that of the London process. 
The conditions necessary to bring about their result, are 
that bi-tartrate of potassa be placed in contact with an excess 
of hydrated sesquioxide of iron, and that they be exposed to 
a temperature not exceeding 140 degrees Fahr., for 24 or 30 
hours. The following formula is founded on the idea sug- 
gested in that paper, and the excellence of the product which 
it yields, renders it deserving of the attention of pharmaceu- 
tists, viz.: 
Take of, Precipitated Carbonate of Iron, three ounces, 
Hydrochloric acid, ten ounces, 
Bi-tartrate of Potassa, seven ounces and a half, 
Water, a gallon and a half, 
Solution of Potassa, five pints and a half, 
Mix the precipitated carbonate of iron with the acid, and 
digest for an hour, or until the former is dissolved, and then 
pour the solution into a gallon of the water, and strain, if 
necessary. To this add the solution of potassa, wash the 
precipitate frequently with water, until the washings are 
wholly without taste, and while yet moist, mix it with the bi- 
tartrate of potassa, and half a gallon of the water. Keep the 
mixture at a temperature between 130 and 140 degrees Fahr. 
for thirty hours in a glass vessel, occasionally stirring, then filter 
the solution through paper, and evaporate to dryness by a 
similar heat, applied by means of a water bath. 
It has been found, in repeating the above process, that the 
required temperature may readily be regulated by putting the 
mixture in a glass jar and placing it in a metallic vessel on a 
support, which vessel is then to be nearly filled with water. A 
thermometer should be suspended in the water, and heat ap- 
plied by means of an alcohol lamp, until its temperature rises 
to 145 degrees; then by regulating the flame for half an hour 
it can easily be ascertained how large it is necessary to be, to 
keep up the required temperature, and the whole operation 
may be left to proceed for hours without any other attention 
