i6o Dr. Thomson on the compounds of chromium. 
I. Chromium. 
The metallic chromium, which I employed in the following 
experiments, had been reduced by Mr. Cooper, of London, 
who possesses great skill in the management of furnaces. He 
was kind enough to give me a specimen of this rare metal 
several years ago ; and I take this opportunity of thanking 
him for a present, which has been of considerable service in 
my investigations. 
Pure metallic chromium is white, with a shade of yellow : 
it is very brittle, and easily reduced to a fine powder, which 
still retains the metallic lustre. It is not sensibly attracted by 
the magnet, even when in very fine powder. Magnetism 
then is not a property of this metal. The specimen found 
magnetic by Richter, must of course have contained iron. 
The specific gravity of chromium I found to be 5 -093 ; but 
the specimen was not quite free from cavities. 
Four grains of this metal, previously reduced to an impal- 
pable powder, were boiled for an hour in nitric acid, without 
perceptible solution. The process was repeated with aqua 
regia instead of nitric acid, and the flask was left for two days 
on the sand bath. It was allowed to remain on the cold sand 
bath from the 3d June to the 18th July, 1826, during a 
period of uncommonly hot weather, when the thermometer in 
the shade was repeatedly at 86°. The acid liquid had assumed 
a green tinge, but the bulk of the powder was not sensibly 
diminished. The undissolved portion being separated, was 
found to weigh 3-73 grains : so that only 0-27 grain had 
been dissolved. 
From this experiment it appears that acids do not answer 
