es: 
Method of preparing Inks, &c. 355 
M. Bosset’s PAPER. 
It is well known that M. Pitel, of Minden, gave the firft 
account of a kind of ink which withftood the oxygenated 
muriatic acid, at the defire of Dr. Lentin, who excited the 
attention of the public to various deceptions practifed at Paris 
‘with common ink by means of the oxygenated rmuriatic acid. 
As this ink confifted merely of a decoction of logwood and 
galls with water, in which fulphate of iron, gum arabic, and 
fugar had been diffolved, and with which indigo and lamp 
black had been mixed mechanically, according to the ana- 
lyfis of M. Weftrumb, it may be eafily explained why it exhi- 
bited fuch different appearances when brought to the teft. 
M. Gruner, apothecary in Hanover, as appears by his letter 
to the editor of the Hanoverian Magazine, was able to obli- 
terate it entirely by the muriatic acid; while, on the other 
hand, its indeftruétibility by that acid is confirmed by 
M. Wiegleb and Thorey. Both are in the right: as foon 
as the ink is well ftirred round, it withftands this acid; but, 
if not ftirred, this acid diffolyes the black oxyd of iron, and 
the paper in the places wrote upon is reftored to its prif- 
tine ftate. Now, though this ink, when ftirred round, does 
not entirely fail of its objec, this circumftance, however, 
may be often forgotten ; and this the more readily, as even 
without ftirring it has all the blacknefs when ufed of com- 
mon ink, on account of the oxyd of iron which it contains. 
Since that time I have made experiments in order to produce 
an ink which might with{tand the oxy-muriatic acid, and yet 
contain no iron. I have been able to accomplith this, as well 
as the compofition of fome other inks which contain iron, 
though it does not make their chief component parts, but 
ferves only to give the ink a black colour. 1 made experi- 
ments alfo with the juice of green plants, according to the 
procefs by which M. Murray made an indeftructible kind of 
ink from the fame fubftances. ~ Iron muft not be the chief 
component part of an ink deflined to withftand the muriatic 
acid, becaufe in the ftate of a black oxyd it is eafily diffolved 
by the acid. But as it acts on vegetable colours only when 
they are capable of taking up oxygen, and does not deftroy 
ZZ2 them, 
