426 On the different Compounds formed ly the 
to us; it remains for me to inquire, if the third species of 
tannin of Mr. Hatchett (formed by the sulphuric acid) is 
acombination analogous to the others. I directed my re- 
searches to the tanning matter obtained from camphor, be- 
cause it is that which particularly engaged the attention of 
Mr. Hatchett. Although I do not think that all the imme- 
diate principles of vegetables, when brought into contact 
with sulphuric acid, would be acted upon precisely in the 
same manner as camphor, J yet have reason to believe, that 
the results presented by this last are applicable to those 
substances which have a similar composition. The sul- 
phuric acid, in its mode of acting, appears in general to pos- 
sess more uniformity than the nitric acid does. The ex- 
periments which I am going to relate, were made upon 
camphor that was perfectly pure. 
I put into a retort, to which a balloon was adapted, thirty 
grammes of camphor and sixty of pure sulphuric acid. 
The mixture became dark and yellow. I exposed it toa 
gentle heat for two hours. _ A great deal of sulphurous acid 
was disengaged. I then ponred upon the thick brown li- 
quor remaining in the retort, sixty grammes of sulphuric 
acid, and distilled. There came over into the receiver weak 
sulphuric acid, sulphurous acid, and a yellow volatile oil 
having a strong smell of camphor. ~ Towards the end of the 
operation there was produced a small quantity of sulphuret- 
ied hydrogen, which was decomposed by the sulphurous 
acid; there was then scarcely any liquor left in the retort. 
The residue, after distillation, was washed in boiling wa- 
ter until the washings were no longer sensibly coloured. 
The first washings contained an excess of sulphuric acid ; 
the others scarcely contained enough to be sensible to ba- 
rytes. IT shall first begin with the examination of the coaly 
residuum, and shall afterwards treat of the matters contained 
in the washings. 
1. Action of Water. 
The coaly residuum was of a bright black colour; its 
taste was a little acid, upon its being held some time in the 
mouth; it shghtly reddened turnsole paper moistened with 
water. When boiled some hours in distilled water, the 
water was scarcely at all tinged. The water thus boiled 
upon the matter, formed no precipitate with nitrate of ba- 
rytes and acetate of lead, even after standing twenty-four 
hours. Evaporated to dryness, there remained a trace of 
brownish colour, which became red on the application of 
barytes water, These trials convinced me there was no 
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