the compounds of chromium. 171 
acid weighs 6 5 ; and 6-5 — I'S = 5 = atomic 'weight of 
green oxide. 
The 5 atoms of sulphurous acid thus formed unite with 5 
atoms of sulphuretted hydrogen; and these two bodies are 
mutually decomposed into 5 atoms hyposulphurous acid and 
5 atoms water. The 5 atoms of hyposulphurous acid uniting 
to the 10 atoms of potash constitute dihypo-sulphite of potash, 
composed of 1 atom hyposulphurous acid 5 
2 atoms potash - - 12 
17 
I conceive that this beautiful example of rather a compli¬ 
cated series of decompositions and new combinations, leaves 
no doubt that the atomic weight of green oxide of chromium 
is 5. 
When we take bichromate of potash instead of neutral 
chromate, and treat it with sulphuretted hydrogen gas, the 
precipitated hydrosulphuret has a buff colour instead of a 
green. This may perhaps be ascribed to a portion of undecom¬ 
posed chromic acid falling in combination with some part of 
the precipitate. For we shall see afterwards a similar coloured 
precipitate composed of chromic acid and green oxide. 
This buff coloured precipitate is tasteless, and insoluble in 
water. It is either a hydrosulphuret of chromium, or at least 
contains a hydrosulphuret; for when it is heated sulphur 
sublimes, and sulphurous acid is given off. At a certain tem¬ 
perature it catches fire, and burns for some time with a yellow 
low flame. When digested in muriatic acid some sulphur 
precipitates. When digested in nitro-muriatic acid, a portion 
of the sulphur is converted into sulphuric acid. From 7-71 
grains of the buff coloured precipitate I obtained 
