20 M. Mitscherlich on the Forms of Artificially Crystallized Salts. 
phates crystallise in exactly the same manner as the Arseniates 
of the same bases, when they are at the same point of satura- 
tion, and contain the same number of atoms of water of crystal- 
lisation, which is generally the case. The protoxides of the five 
following metals, viz. iron^ zinc^ cohalf ^ nickel^ and manganese ; 
the deutoxide of copper^ and also lime and magnesia^ re- 
place one another mutually, provided always, that in the com- 
binations which are examined the number of atoms of water be 
the same. Alumine^ the deutoxide of iron, and also that of man- 
ganese, may also be substituted for one another, without any 
change of form. Barytes, strontian, and the oxide of lead, are 
in the same predicament, and also chlorine and iodine, and sul- 
phur and selenium, &c. To these dijfferent groups, M. Mitscher- 
lich has given the name of Isomorphous Bodies. 
This ingenious chemist is at present occupied in determining 
how many of such isomorphous groups exist among simple 
bodies, and among their different degrees of oxidation ; and al- 
so in determining to what isomorphous group each of them be- 
longs. 
The discoveries of M. Mitscherlich throw great light upon 
mineralogy, and will give a key to an explanation of the contra- 
dictions of chemical analysis, and of the geometrical measure- 
ments of crystals ; because, in a mineral species whose form has 
been determined with the' greatest certainty, one or more ele- 
ments may vary, provided that they belong to the same isomor- 
phous class, and that the other elements remain the same. 
Hence, it is for this reason that lime^ magnesia, the protoxide 
of iron, and the protoxide of manganese, are substituted for one 
another in the Amphiboles and the Pyroxenes. 
M. Mitscherlich has found also, that when several combina- 
tions, isomorphous salts, for example, are mixed in the same li- 
quid, and when this liquid is afterwards evaporated, the isomor- 
phous salts crystallise together, forming a part of the same cry- 
stal, and their relative proportion is then determined only by 
the relative quantity of each which the liquid has had to aban- 
don at the moment of crystallisation. The crystal, in short, is, 
as it were,' built of isomorphous molecules, without any chemical 
affinity having a share in it, and without our being able to per- 
ceive fixed and determinate proportions. This experiment is 
