348 On two new Compounds 
bon, I shall have less occasion to dwell on the proofs that the 
compound I am about to describe, is also a binary combination 
of carbon and chlorine. 
When the vapour of the perchloride of carbon is heated to dull 
redness, chlorine is liberated, and a new compound of that ele- 
ment and carbon is produced. This is readily shown by heating 
the bottom of a small glass tube, containing some of the per- 
chloride in a spirit lamp. The substance at first-sublimes ; but 
as the vapour becomes heated below, it is gradually converted 
into protochloride, and chlorine is evolved. 
It is not without considerable precaution that the protochlo- 
ride of carbon can be obtained pure; for though passed through 
a great length of heated tube, part of the perchloride frequently 
escapes decomposition. The process I have adopted is the fol- 
lowing : Some of the perchloride is introduced into the closed end 
of a tube, and the space above it, for 10 or 12 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 receivers 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 application 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, all the chlorine may be driven off without 
any loss of the substance, and it becomes limpid and colour- 
less. It still, however, always contains some perchloride, which 
has escaped decomposition ; and, to separate this, | have boiled 
the fluid until the tube was nearly full of its vapour, and then 
closing the end that still remained open, by a lamp and blow- 
pipe, have afterwards left the whole to cool. It is then easy, 
by collecting all the fluid into one end of the tube, and introdu- 
cing that end through a cork into a receiver, under which a very 
small flame is burning, to distil the whole of the fluid at a tem- 
perature very little above that of the atmosphere. The solid 
chloride being less volatile does not rise so soon, and the pure 
protochloride collects at the external end of the tube. ‘To as- 
certain its purity, a drop may be placed ona glass plate; it will 
immediately evaporate, and if it contains perchloride, that sub- 
stance will be left behind; otherwise, no trace will remain on 
the glass. ‘The presence or absence of free chlorine may be as- 
certained 
