200 
Dr. Thomson on some of 
When chloro-chromic acid is left exposed to the air, it 
gradually loses its smell and its red colour, and is converted 
into an opaque dark brown liquid, having an acid and astrin- 
gent taste, without the least perceptible sweetness. When 
this liquid is saturated with carbonate of ammonia, a yellowish 
brown precipitate falls, which becomes blue when washed, 
and is merely protoxide of chromium. The filtered liquid is 
yellow-coloured, and consists of a mixture of chromate of 
ammonia and sal ammoniac. 
In some cases, when the chloro-chromic acid had been 
left for some days exposed to the air, it was converted into a 
solution of muriate of chromium in water ; but this change 
was not constant. I ascribed it at first to small pieces of 
cork which had accidentally fallen into the liquid which had 
undergone this alteration ; but upon trying whether I could 
convert chloro-chromic acid at pleasure into muriate of chro- 
mium, by leaving it in contact with cork, the experiment did 
not succeed. I am disposed however to ascribe the alteration 
to the action of combustible matter, as spirits and oils cau- 
tiously added convert it into a green coloured matter which 
has a considerable resemblance to muriate of chromium. 
When chloro-chromic acid is exposed to heat in an open 
vessel much chlorine flies off', and a black scaly matter 
remains, which speedily deliquesces in the air, and when 
heated melts and gives out the odour of chlorine gas. 31 
grains of this scaly matter were left for a month in an open 
dish covered with paper in my laboratory, which is rather 
damp. It was converted into a brown opaque liquid, weigh- 
ing 58*36 grains. It had therefore absorbed 27*36 grains of 
water. The liquid being diluted with water and filtered, 
