ON THE DOUBLE SALTS OF IRON. 
99 
results are not coincident with the opinions of some others: 
the writer in the Pharmaceutical Journal, to whose paper I 
have alluded, after a description of M. Beral's process, has 
the following — " The oxide of iron and citric acid combine 
in the proportion of forty parts of the oxide to seventy of 
the crystallized acid." The same is repeated by Dr. A. T. 
Thomson, in the last edition of his work on Materia Medica. 
1 have repeatedly tried, without success, but with some uni- 
formity as to result, to obtain a citrate of iron in scales so 
constituted ; and as these proportions seem more fitly to 
apply to a compound of a different description, I would re- 
spectfully leave to these gentlemen to determine whether 
some error in computation may not have attended their in- 
vestigations. 
Regarding what has been stated in the preceding cases 
as matter of evidence, I see not how to escape from the 
conclusion, that in case 3, and latter part of case 4, we are 
presented with definite compounds of sesquioxide of iron 
with citric and tartaric acids ; indeed, the constitution of 
the tartaric acid salts determined theoietically, and by ex- 
periment, agreed so very closely as to leave little room for 
dispute, and with the citric acid salt it is not. much more dis- 
cordant. The combination of the oxide with acetic acid is 
also to be considered as definite, inasmuch as all acid un- 
combined must have escaped during the evaporation. The 
quantity of oxide in twenty-five grains of the dry salt held 
a few minutes before the fire, was found to be nearly eight 
grains; but this estimate, owing to causes before mentioned, 
is a trifle too high: now, by a theoretical computation, a 
salt composed of four equivalents of acetic acid, and one 
equivalent of oxide of iron, should contain seven grains 
(rather more than less) of oxide in the same quantity ; 
which, therefore, is probably the actual constitution of the 
article in question. 
But it may fairly be doubted whether the products of the 
first and second operations have an equivalent constitution; 
