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NEW PA TEN Te 
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the offices of Enrollment, in Chancery-lane. 

Br. DesMonpD’s TANNING PROCESS. 
N the 15th of January, letters patent 
were granted to Mr. WILLIAM 
DeEsmonp, No. 6, New Palace-yard, 
Weftminfer, for his invention of a 
method of tanning all forts of hides and 
fkins, and of rendering more folid and 
incorruptible in water, feveral vegetable 
and animal fubftances, fuch as flax, hemp, 
cotton, filk, hair, wool, &c. as well as 
the manufactures made thereof. 
The principle of this invention is ex- 
lained in the fpecification, by the fol- 
owing account of the procefs :— 
et Provide five veffels, called digettors, 
With an aperture at the bottom of each: 
and let them be elevated upon ftillages. 
Fill the digeftors withtan; peur water 
on the tan in the firft digeftor, and 
draw it off prefently afterwards; pour 
this liquor on the tan in the fecona di- 
geftor, draw it off, and pour it into the 
third, and fo on till it comes through the 
fith and laf digeftor. The liquor is 
then highly coloured, and marks from 
fix to eight degrees on the hydrometer 
for falts. “Fins liquor may be called 
the tanning iturin. It has this pecu- 
}iak property, that if on a fmall quantity 
be pourcd a few drops of a folution of ’ 
animal glue, the liquor which before _ 
was clear becomes turbid, and a whitith 
fubftance falls to the bottom of the glafs. 
The precipitate thus obtained by means 
of the folution of glue, 1s a fure indi- 
cation thac the liquor contains the tan- 
ning principle ; for this reafon, that glue 
being of the fame nature with the fkins 
or hides of which it ig made, whatever 
fubftance unites itfelf mndiffolubiy with 
the former, will do fo likewife with the 
latter. This folution is made by diffelv- 
ing a little common giue in water over 
a moderate fire; by means of it not ‘only 
oak*bark, but alfo the bark of feveral 
other trees, fuch as plane-tree, chefnur- 
tree, the American hemlock-tree, pop- 
Jar, elm, willow, &c. as weil as divers 
farubs and plants, fuch as myrtle, &c. 
all of which [ call tan,-are found to con- 
tain the tanning principle; and by em- 
ploying the folution as above, it will in 
all cafes be eafy to afcertain, whether 
any given fubftance contains this prin- 
ciple or not. ae 
‘In the courfe of thefe Itxiviations, 
two things will be obferved; firft, the 
liquor running from the firft digefior, at 
length lofes its colour: if in this fiate 
a little of it be taken in a glafs, and the 
former experiment be repeated, the li- 
quor no longer becomes turbid, but 
remains clear, which fhows it euntsins 
no more of the tanning principle ; but if 
ou pour into the fame glafs a few drops 
of fulphat of iron, the liquor becomes 
thick and black. This liquor is not te 
be poured on the tan in the fecond di- 
geftor, but is to be laid by and ufed for. 
the depilation, or taking off of the hair or 
wool. It is diftinguithed by the name of. 
gallic lixivinn, becaufe it appears to 
contain the fame principle as galls. 
' © The fulphat of iron is obmined, by 
diffolving a fmall quantity of irom in oil 
of vitriol, dilured with water; or by dif- 
folving green copperas in water. This 
folution ferves to afcertain fuch fub- 
{tances as contain the ga/ic principle, 
Lime-water will alfo produce this ef- 
fect. 
_ When the liquor ceafes to grow black, 
by the mixture of the fulphat of iron, 
ir will be ufelefs to pour any more water 
on the tan in the firft digeftor. This 
tan, being exhaufted both of the sang 
and gallic principles, mutt be removed, . 
and new tan put in its place. 
“© It will be obferved, fecondly, that the 
liquor after running through all the 
digeftors, at lalt grows weak. Add ta 
your ftock of fanning Hervium, all the 
liquor that makes from fix to eight 
degrees on the hydrometer ; what after- 
wards proceeds from the laf digeftor, 
is to be poured on the new tan in the 
firft; then the frefh water is to.be con- 
veyed on the tan m the fecond digeftor, 
and the liquor of the firit to be laid by, 
while it marks fix or eight degrees on the 
hydrometer, anq added to the sanaing 
Irxivium, which mutt always be carefully 
feparated from the gal. In this man- 
ner, the tan in alk the digeftors may be 
renewed, 
