•456 i>. Blagden's Obfervatlons on 
to bring the blotting paper in contafl with the letters, becaufe 
the colouring matter is foft whilft wet, and may eafily be rubbed 
off. 
The acid I have chiefly employed has been the marine ; but 
both the vitriolic and nitrous fucceed very well. They fhould 
undoubtedly be fo far diluted as not to be in danger of cor- 
roding the parchment, after which the degree of ftrength does 
not feem to be a matter of much nicety. 
The method now commonly pra&ifed to reftore old writings, 
is by wetting them with an infufion of galls in white wine *. 
This certainly has a great effe£l; but it is fubje£l, in fome degree, 
to the fame inconvenience as the phlogifticated alkali, of flam- 
ing the fubflance on which the writing was made. Perhaps if, 
inflead of galls themfelves, the peculiar acid or other matter 
which flrikes the black with iron were feparated from the 
fimple aflringent matter, for which purpofe two different pro- 
ceffes are given by Piepenbring + and by Scheele J, this 
inconvenience might be avoided. It is not improbable like- 
wife, that a phlogifticated alkali might be prepared, better 
fuited to this objefl than the common ; as by rendering it 
as free as poftible from iron, diluting it to a certain degree, 
or fubftituting the volatile alkali for the fixed. Experiment 
would moft likely point out many other means of improv- 
ing the procefs defcribed above ; but in its prefent ftate I 
* See a complicated procefs for the preparation of fuch a liquor in Canepa- 
aius, De Atramentis, p. 277. 
f Crell. Annal. 1786, B.I. p. 51. 
I Kongl. Vetenfk Acad* Nya Handlingar, tom. VII. p. 30. See alfo M. 
de Morveau’s account of this fubflance in the Encyclopedic par ordre des 
matieres. 
I 
hope 
