170 
ON PERCHLORIDE OF IRON. 
preparation of hydrated perchloride of iron, but none of 
these are adapted for obtaining it readily, of uniform com- 
position, entirely soluble, and susceptible of long preserva- 
tion. The principal cause of the easy alteration which the 
chloride of iron undergoes when prepared by either of the 
processes described above, seems to be the large quantity 
of water which it retains. Thus, that of M. Beral, which 
contains the least, affords, soon after its preparation, a per- 
ceptible deposit of oxychloride, when dissolved in water. 
Induced by M. Soubeiran to seek a practical process for 
obtaining, in a short time, a perfectly soluble perchloride 
of iron, of a sufficiently uniform composition to admit of its 
strength being easily estimated, I believe I have succeeded, 
by submitting a solution of sesquioxide of iron in hydro- 
chloric acid to evaporation under the two following con- 
ditions: first, evaporation at a temperature not exceeding 
212° Fahr.; secondly, evaporation in perfectly dry air. 
After several experiments, the following is the process at 
which I have stopped: — Take of haematite, that which mi- 
neralogists denominate concrete red oxide of iron, (fer 
oxyde rouge co7icr£tionn6,J reduced to powder by pound- 
ing and triturating in small quantities at a time in an iron 
mortar ; introduce this into a stoppered bottle, and add to 
it pure concentrated hydrochloric acid in such quantity that 
there shall be an excess of haematite ; then agitate the mix- 
ture. The two bodies soon react upon each other, produc- 
ing water and perchloride of iron, accompanied with the 
disengagement of heat. This first action having subsided, 
place the bottle near the fire, and shake it from time to time. 
After remaining in contact for several hours, allow it to 
deposit, and then filter the solution. The filtered liquor is 
received in a porcelain capsule, which is placed either on 
sand heated by steam, or over the mouth of a cucurbit, 
taking care to interpose a piece of flannel between the cap- 
sule and the cucurbit, which should be tied on to keep it in 
its place. The apparatus should be so arranged that the 
