144 PREPARATION OP THE PERCHLORIDE OP IRON. 
of iron, dissolving heematite by digestion in commercial 
hydrochloric acid, and boiling towards the end of the ope- 
ration. The liquid is allowed to clarify, is then evaporated 
to the consistence of a liquid syrup, and placed well cover- 
ed, in a cold situation, for instance in a cellar, where it be- 
gins to crystallize after some days, and continues to do so 
for some weeks ; the mother-water is decanted and the crys- 
tals preserved. M. Mohr analysed the crystals prepared 
in this manner, and found them to contain 12 atoms of 
water; he has consequently assigned to it the formula 
Fe2Cl 3 + 12HO. 
M. Fritzsche, who undertook a fresh investigation in or- 
der to determine the proportion of water contained in the 
chloride of M. Mohr, found that this chloride gave very dif- 
ferent results on analysis with respect to the quantity of 
water, which is equally the case with those obtained by 
the process described by Orfila, Thenard and Berzelius, 
and that it was impossible to decide whether it contained 
10, 11 or 12 atoms of water; with 10 atoms it should 
contain 35.92 per cent., with 11, 38.15, and with 12, 40*22. 
According to the same chemist, on leaving the preceding 
chloride under a bell-glass with sulphuric acid, the crystals 
are again convertrd into a thick liquid, which gives rise to 
other crystals,, containing from 21 to 23 per cent, water ; 5 
atoms would require 2 1 . 9 per ct. According to M. Fritzsche, 
the same crystals are obtained by fusing the chloride 
with 10, 11 or 12 atoms of water and evaporating until 
a drop solidifies on cooling, and then adding a few drops 
of concentrated hydrochloric acid before placing it aside 
to cool. 
M. Fritzsche has been led by his experiments to admit 
the existence of two hydrates of the perchloride of iron per- 
fectly crystalline, between which there is no other crystalline 
combination. 
It will be seen from the above that the processes which 
have been, described for the preparation of the hydrated 
