On the Composition of Writing Ink. 45 
per and forms above It undulated lines of a yellow co« 
lour. 
We may succeed, however, in softening both these 
effects, by taking the precaution to dilute the nitric 
acid with a sufficient quantity of water, or to wash 
the paper immediately after the writing has been taken 
out. 
A mixture of the muriatic and nitric acids has but a 
slow action upon writing. It bleaches the paper and does 
not oppose its desiccation, as when we employ the nitric 
acid alone. 
In general, whatever be the kind of acid employed 
to discharge writing, it is always proper when the 
operation is performed to dip the paper in water, in or- 
der to dissolve the new combinations which the acids 
have formed with the particles of ink which have been 
discharged. 
M. Tarry, at the conclusion of this article, does not 
fail to observe that China ink does not act like common 
ink with the acids, as its composition Is quite different 
from that which we use for writing of all kinds. Bo far 
from the acids attacking China ink, they make it, on the 
contrary, of a deep black: it cannot be discharged there- 
fore without erasing it. 
ARTICLE II. 
Processes for ascertaining what Writing has been sub- 
stituted for something taken out , and Methods of re- 
viving the ft riting which has disappeared. 
All the methods which have been given for discharg- 
ing writing consist, as abovementioned, in decomposing 
the ink and in forcing its constituent parts to form other 
combinations. These combinations, being decomposed 
in their turn by different agents, may regain a tint, which, 
