292 Mr. Hatchett’s additiona l Experiments 
When the retort became warm, and after the expulsion of 
the atmospheric air, a very small portion of water arose, which 
settled like dew on the sides of the vessels ; this was succeeded 
by a little nitric acid, from which the tanning substance had 
not been completely freed, and soon after a yellowish liquor 
came over, which was in so very small a quantity as only to 
stain the upper part of the neck of the retort : as nothing more 
seemed to be produced, I then raised the fire, when suddenly 
the vessels were filled with a white cloud, and so great a por- 
tion of gas was almost explosively produced, as to overset the 
jar ; this gas, by its odour, appeared to be ammonia, which in 
the first instance had formed the white cloud, by combining 
with the vapour of the nitric acid with which the vessels were 
previously filled.* Another jar was speedily placed in the 
room of that which had been overturned, and a quantity of gas 
was slowly collected ; this proved to be carbonic acid, except- 
ing a very small part, which was not taken up by solution of 
caustic potash, and which as far as the smallness of the quan- 
tity would permit to be determined, appeared to be nitrogen 
gas. There remained in the retort a very bulky coal, which 
weighed eight grains and a half ; this by incineration yielded 
one grain and a half of brownish white ashes, which consisted 
principally of lime, but whether any alkali was also present I 
cannot positively assert, as the trace which I thought I discovered 
of it was very slight. 
I shall for the present postpone any remarks upon this expe- 
riment, as I wish to proceed in the account of others which 
have been made on the artificial tanning substance. 
G. Fifty grains of this substance were dissolved in four 
* After the experiment the receiver was found to be thinly coated with a white saline 
crust. 
