WRITING INK. 
Considera- mk, SO oblamedj may not prove so durable as other ink con- 
tions as to the . . . ^ / r 
ingredients taming a tulJ proportion of the less soluble, but more stable, 
portims*^ colouring matter of galls. It is, therefore, with 
good reason, that Lewis, Chaptal, and others, have recom- 
mended boiling to extract the whole of the soluble matter con- 
tained in galls, especially as oxigen will be absorbed during the 
ebullition, and this absorption will contribute to give the ink its 
full degree of blackness so much the more speedily. 
Ink, in which the colouring matter of logwood bears a large 
proportion, will be made red by applying muriatic acid to it ; 
this redness, however, will soon disappear, and the former 
blackness be restored, partly, at least, in consequence of the 
volatility of the acid. 
* _ t / 
ft does not appear, that any considerable advantage is gained 
by substituting any of the other acids for the sulphuric, to dis- 
solve iron for making ink, though the case is different in regard 
to dyeing and calico-printing. 
I have already observed, that an excess of sulphate of iron 
produces ink of a blueish tint, which, if the excess be great, 
will, at no remote period, become yellow j probably, because 
the affinity of the metallic oxide for oxigen, not being coun- 
teracted by a sufficient portion of vegetable matter, the latter 
will gradually suffer a decomposition from the excess of oxigen 
absorbed, and at length the oxidated iron alone will remain. 
A similar effect will, indeed, take place, after a long course of 
years, even when there is no disproportion of iron ; but it will 
be retarded by increasing the proportion of galls beyond that 
which produces the blackest colour : and, indeed, by such an 
increase as to make the ink incline considerably from what ii 
deemed a good black, towards a brownish purple. 
But, unfortunately, that ink in which the proportion of galls 
is greatest, is the most disposed to become mouldy j a defect 
which it is difficult, if not impossible, to hinder, in any con- 
siderable degree, so long as ink retains the mucilaginous part of 
the galls, which water always extracts along with the colouring 
matter. It has, indeed, been found, that by keeping a saturated 
infusion or decoction of galls, six or eight months, more or less, 
accordins 
