179 
the compounds of chromium . 
colour. By this process the powder was converted into a 
phosphate of chromium. Part of the phosphoric acid was 
withdrawn, and remained dissolved in the liquid ; for the 
phosphate weighed 9' 545 grains. It was obviously a com- 
pound of 
Protoxide of chromium 5*08 or 5 or 1 atom. 
Phosphoric acid - 4*465 4*394 ij atom. 
There is still an excess of acid ; but the excess, instead of 
being half an atom, as in the phosphuret, was only ^d of an 
atom. 
My attempts to form a sulphuret of chromium by a similar 
process were not attended with success. 
3. Besides the preceding experiments, by which the atomic 
weight of green oxide of chromium was determined, many 
others were tried, which did not terminate so satisfactorily. 
It will be worth while to give a short account of a few of the 
most promising of these methods, though they did not prove 
successful. 
1 . A quantity of chromate of lead was heated to whiteness 
in a charcoal crucible. It became black and agglutinated, 
and globules of metallic lead were visible in it. The under 
side of the cohering mass consisted chiefly of green oxide of 
chromium. 23-06 grains of this black matter were digested 
for a month in dilute nitric acid, and then filtered. The 
undissolved green oxide of chromium being collected on a 
filter, edulcorated, dried, and ignited, weighed 5*589 grains. 
The nitric acid solution being evaporated to dryness, left 
27 grains of pure nitrate of lead, equivalent to 18-216 grains 
of protoxide of lead. Thus the 23*06 grains of black matter 
furnished 
