354 Method of preparing Inks, &c. “ 
paper by Philip Chriftian Pitel of Minden *, in which he 
recommended an ink, difcovered by him, which was inde~ 
ftructible, and could be obliterated neither by the oxygen-, | 
ated muriatic acid, nor by any other. ,corrofive fubftance. 
This induced M. Wehrs to examine this ink, and the fame 
thing was undertaken by M. Gruner. According to their 
experiments, this ink, however, was obliterated in the courfe 
of nine hours by the oxygenated muriatic acid, and alfo by 
cauftic pot-afh; but at the fame time an opinion entirely 
oppofite was announced by Dr. Lentin t, M. Thorey §, and 
M. Wiegleb ||, who all, in confequence of their having em- 
ployed the fame teft, declared the ink to be indeftruétible. 
Thefe different opimions are therefore directly contrary to 
each other. M. Gruner found that the ink could be de- 
{troyed by the oxgenated muriatic acid, and by cauftic al- 
kali: M. Thorey obferved, that its blacknefs was only lef- 
fened by the oxygenated muriatic acid, and by the vapour 
of that acid. He found, however, as M. Gruner did, that the 
cauftic alkali diffolved the ink entirely from the paper,. but 
that, like feveral acids, it deftroyed the paper. M. Lentin and 
Wicgleb deduced from their experiments, thofe of the for- 
mer cbairig made with oxygenated muriatic acid, ‘and thofe 
of the bidet with the fame, as well as feveral other acids, and 
even cauttic alkali, that this ink was entirely indeftructible. 
Thefe contradictory refults M. Weftrumb endeavoured to re- 
folve in his examination of Pitel’s indeftru@iible ink, which 
he found to be only common ink mixed with indigo; and he 
propofed the following mixture for an ink which could not 
be deflroyed :—Boil 1 0z. of Brafil wood, and 3 ozs. of pul- 
verifed galls, with 46 oz. of water; ftrain the liquor, which 
mutt be boiled down to. 32 ozs., and pour it, ftill warm, over 
14 oz. of perfectly pure fulphate of iron, 14 oz. of gum ara- 
bic, and 2 0z. refined fugar. When thefe ingredients are 
diflolved, add from 1 to 14 02. good indigo ground exceed- 
ingly fine, and 3 oz, of purified lamp black. 
* Hannov. Mag. 1797, part 77. + Ibid. t Ibid. p. r223. 
§ Ibid.1797, part 97. || Reich’s Anzeiger 1797, No- 297. 
M. Bossx’s 
