Mr. Hatchett on an artificial tanning Substance. 219 
In these experiments, the deal and the teak wood had been 
reduced to the state of coal, as usual, by fire, but as this does 
not appear to have been the means generally employed by 
nature to convert organized substances into the varieties of 
mineral coal, I for a considerable time, previous to the disco- 
very of the artificial tanning product, had been employed in a 
series of experiments on the slow carbonization of a great 
number of vegetable substances by the humid way. 
The agent which I most commonly used to produce this 
effect, was sulphuric acid occasionally, diluted ; and although 
many of the processes were extremely unpleasant and tedious, 
yet I have not any reason to regret the time which has been 
thus employed. The subject however I foresee will branch 
out into several details, none of which as yet I can regard as 
sufficiently completed to merit the honour of being submitted 
to this learned Society ; but I am in a manner almost compelled 
in the present case to anticipate a few of the experiments, 
with their results, because they are intimately connected with 
the subject now under consideration. 
In these experiments, I have observed that concentrated 
sulphuric acid, when poured upon any of the resinous sub- 
stances reduced to powder, dissolved them in a few minutes ; 
at this period the solution was transparent, commonly of a 
yellowish-brown colour, and of the consistency of a viscid oil. 
But if, after this, the vessel was placed on a sand-bath, the colour 
of the solution became progressively darker, sulphureous gas 
was evolved, and at length the whole appeared like a very 
thick liquid of an intense black. I purposely for the present 
pass over many phenomena, some of which are peculiar to the 
different substances when thus treated, whilst others are 
Ff 2 
