96 
ON THE DOUBLE SALTS OF IRON. 
ART. XXIV. — ON THE DOUBLE SALTS OF IRON. 
By Mr. Hemingway. 
In case 1, hydrated sesquioxide of iron was added to a 
boiling and concentrated solution of citric acid: it was ob- 
served to dissolve readily and in large quantity up to a cer- 
tain point. A further addition left the solution turbid, ap- 
parently from excess of oxide. The mixture was now suf- 
fered to cool, was then filtered, evaporated to a treacly 
consistence, and dried in thin layers on well glazed earthen- 
ware: it separated in lamellas of anacicular form and garnet 
color, scarcely soluble in cold water, but more readily in hot. 
Fifty grains of this salt, dried at 212°, were examined as to 
the quantity of oxide contained ; it yielded fourteen grains 
=28 per cent. Another portion, prepared after the same 
manner, yielded fifteen grains=30 per cent. 
In case 2, two several quantities of citric acid and hy- 
drated sesquioxide of iron were kept at a temperature just 
sufficient to influence to combination until chemical action 
had ceased. The solutions were filtered, reduced, and dried, 
as in case 1. The salts separated in lamellae, but of a short 
and broad sort. These were in like manner submitted to 
examination, when there were found in one 22 grains of 
oxide, and in the other 2d grains of oxide, per cent. 
In case 3, 1 proceeded as in case 1, until the whole of 
the oxide derived by precipitation from four parts and a 
half of commercial sesquioxide had been added to five parts 
and a half of crystallized citric acid, and gentle ebullition 
was continued for fifteen or twenty minutes. In appearance 
much of the oxide remained unchanged ; but it was evi- 
dently in combination, for on the addition of an alkali, it 
was totally and instantly dissolved. Owing to the variable 
quantity of real oxide existing in the article sold in the 
