316 Mr. Hatchett's Analysis of 
This gas I afterwards examined, and found that it possessed 
all the properties of the azotic gas.* 
I afterwards distilled 100 grains of the yellow oxyde of iron, 
mixed with 200 grains of sulphate of ammoniac. 
Pure ammoniac first came over, and afterwards some sul- 
phureous acid. When the retort began to melt I removed it, 
and found the iron chiefly in the state of the red oxyde, or 
colcothar, mixed with some sulphate of iron. 
When oxyde of zinc was used, the residuum was sulphate of 
zinc. 
Minium, when triturated with sulphate of ammoniac, im- 
mediately decomposed it like lime, or the alkalies, and when 
distilled, the retort contained sulphate of lead. 
When native green oxyde of copper was distilled with sul- 
phate of ammoniac, the residuum was partly red oxyde of cop- 
per, with some sulphate of the same. But the ammoniac came 
over in a concrete state, by reason of the carbonic acid con- 
tained in the green oxyde. 
The oxydes therefore of iron, zinc, lead, and copper decom- 
pose the sulphate of ammoniac by combining with the acid. 
I next mixed it with the yellow tungstic acid ; but after the 
distillation, I found the tungstic acid unchanged, excepting 
that it had acquired a tinge of pale green. The ammoniac 
* This operation requires to he conducted with caution ; for at the moment when 
the white cloud appears, a vacuum takes place, occasioned by the alkaline gas (which 
previously filled the vessels) being neutralized by the sulphureous gas, which is then 
produced. It is necessary, therefore, in about io or 15 minutes after the commence- 
ment of the operation, that the fire should be raised, and the azotic gas will then soon 
begin to pass Into the jar. Some water will most commonly rush into the receiver, 
but if the capacity of this is not too small, there will not be time enough for the water 
±0 rise sufficiently high, so as to pass into the retort. 
