302 Mr. Hatchett's additional Experiments 
Sir Joseph Banks ; for although this decoction did not afford 
an immediate precipitate with solution of gelatine, and although 
the precipitate was also apparently dissolved by boiling water, 
yet upon cooling, the same precipitate was reproduced in its 
original state. I am therefore inclined to believe, that the 
tanning substance is really developed in many of the vegetable 
bodies by heat, but that a certain degree of temperature, not 
very easy to determine, is absolutely requisite for this purpose. 
Before I conclude this section, it may be proper to observe, 
that when a small quantity of nitric acid was added to any of 
the above-mentioned decoctions, and when these had been 
subsequently evaporated to dryness, and afterwards dissolved 
in distilled water, they were converted into a tanning substance 
perfectly similar to that which is produced by the action of 
nitric acid on the varieties of coal. 
§VI. 
In the preceding Paper, a variety of the tanning substance 
was slightly noticed, which was formed by the action of sul- 
phuric acid upon common resin, elemi, amber, &c. &c. and 
as an instance has occurred of the formation of the same sub- 
stance from camphor, accompanied by circumstances which 
tend to increase our knowledge of the properties of the latter, 
I shall here describe this experiment. 
Experiment on Camphor with sulphuric Acid. 
The effects produced on camphor by sulphuric acid have 
been but very superficially examined ; for all that has hitherto 
been stated amounts to this, that camphor is dissolved by sul- 
phuric add, that a brown or reddish-brown solution is formed. 
