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XII. On an artificial Substance which possesses the principal cha- 
racteristic Properties of Tannin. By Charles Hatchett, Esq. 
F.R.S. 
Read April 25, 1805. 
si- 
rp 
1 he discovery of the principle on which the effects of 
tanning essentially depend, may be partly attributed to Mr. 
Deyeux, who obtained a substance from galls which he con- 
sidered as a species of resin,* but which was afterwards 
proved by Mr. Seguin to be that which renders the skins of 
animals insoluble in water, and imputrescible, and thus to be 
the principle by which they are converted into leather. -f 
The chief characteristic property of this substance was 
ascertained by Mr. Seguin to be that of precipitating gelatine 
or glue from water in a state of insolubility, and as it was evi- 
dently different from any vegetable substance hitherto disco- 
vered, lie gave it the name of tannin. 
This discovery of Mr. Seguin at once unveiled the theory 
of the art ; an easy and certain method was afforded by which 
tannin could be detected, and its relative quantity in different 
substances be determined, whilst the nature and properties of 
this newly discovered vegetable principle could be subjected 
to accurate investigation. 
* Memoirc sur la Noix de Galle, par M. Deyeux ; Annates deCbimie, Tome 
XVII. p. 23. f Ibid. Tome XX. p. 15. 
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