of chlorine and carbon , &c. 65 
by heating the bottom of a small glass tube, containing some 
of the perchloride, in a spirit lamp. The substance at first . 
sublimes, but as the vapour becomes heated below, it is gra- 
dually converted into proto-chloride, and chlorine is evolved. 
It is not without considerable precaution that the proto- 
chloride of carbon can be obtained pure ; for though passed 
through a great length of heated tube, part of the perchlo- 
ride frequently escapes decomposition. The process I have 
adopted is the following : some of the perchloride is intro- 
duced into the closed end of a tube, and the space above it, 
for ten or twelve inches, filled with small fragments of rock 
crystal ; the part of the tube beyond this is then bent up and 
down two or three times, so that the angles may form re- 
ceivers for the new compound ; then heating the tube and 
crystal to bright redness, and dipping the angles in water, 
the perchloride is slowly sublimed by a spirit lamp, and, on 
passing into the hot part of the tube, is decomposed ; a fluid 
passes over, which is condensed in the angles of the tube, and 
chlorine is evolved : part of the gas escapes, but the greater 
portion is retained in solution by the fluid, and renders it 
yellow. Having proceeded thus far, by the careful ap- 
plication of a lamp and blow- pipe, the bent part of the tube 
may be separated from that within the furnace, and the end 
closed, so as to form a small retort ; and on distilling the 
fluid four or five times from one angle to the other, ail the 
chlorine may be driven 01T without any loss of the sub- 
stance, and it becomes limpid and colourless. It still, how- 
ever, always contains some perchloride, which has escaped 
decomposition, and, to separate this, I have boiled the fluid 
until the tube was nearly full of its vapour, and then closing 
mdcccxxi. K 
