198 Progress of Foreign Science. 
Art. XIII. PROGRESS OF FOREIGN SCIENCE. 
CHEMICAL SCIENCE. 
I. Laws or ComBINnaTION. 
On the Relation which exists between Crystalline Form and 
Chemical Proportions. By Mr. E. Mitscherlich*. 
The light which the theory of definite proportionals has thrown 
upon chemistry, the mechanical views by which the atomic 
philosophy accounts for fixed proportions, the use which has 
been made of these views to represent bodies composed of a 
determinate number of atoms, have engaged M. Mitscherlich to 
examine the following problem: Different elements being com- 
bined with the same number of atoms of one or of several other 
elements, have they the same crystalline form? Is the identity 
of the crystalline form determined only by the xwmber of atoms ? 
Is this form independent of the chemical nature of the elements ? 
Accident led him, in his first endeavours, to a series of com- 
binations which furnished an affirmative reply to all the pre- 
ceding questions, so that he was on the point of regarding his 
results as a general law. He operated at first on some single and 
double sulphates ; that is to say, on the sulphates of potash, 
ammonia, and magnesia, of the protoxide of iron and manganese, 
of the oxide of zinc, copper, cobalt, and nickel. But having ex- 
tended his researches to combinations of the same base with 
other acids, which, according to the atomic theory, have the 
same number of atoms as sulphuric acid, or to combinations 
of sulphuric acid with bases having an analogous composition, 
he found that this identity of crystalline form did not necessarily 
hold. This observation induced him to make researches on tlre 
chemical combinations which, by the atomic theory, seem to 
have an analogous composition, in order to study the cause 
of the identity or difference of their crystalline form. The trials 
made with this view seem to demonstrate that certain different 
elements, combined with the same number of one or of several 
elements, affect the same crystalline form; and that chemical 
elements, in general, may in this respect be classed in groups. 
He gives the epithet zsomorphous to those elements which belong 
to the same group, in order to express this quality of the ele- 
ments by a technical term. He has not been able hitherto to 
investigate how many isomorphous groups there are, nor to 
determine all the elements which belong to one or other of these 
groups. Perceiving, however, that a vast field was opened to 
new researches, and that a key was given to lay open a ques- 
tion of so great importance to chemistry, a question at the same 
* Translated from the Memoirs of the Academy of Stockholm, by the 
author, for the Annales de Chim. et de Phys., xix..350. 
