WRITING INK. 
equal parts of galls, and sulphate of iron are directed ; and in 
others, six times as much in weight of the former as of the 
latter. Certainly galls from different species of oak, and from 
different countries, vary much in their -comparative proportions 
of colouring matter j and even among those which are com- 
monly called the best Aleppo galls, one pound of the heavy blue, 
or unperforated galls, will commonly prove equal to one pound 
and one half of the white , from which the insect has escaped, 
and which, from their having been longer upon the tree, with 
large perforated or open cavities, exposed to the weather, and 
particularly to rain, will have suffered a considerable loss of 
colouring matter. These two sorts of galls, as commonly im- 
ported, are mixed together in nearly equal portions, and are 
then called galls in sorts , which are to be understood as meant 
by me when the contrary is not expressed. 
Of such galls, I think, from the results of numerous expe- 
periments, that three pounds will afford the most suitable pro- 
portion of colouring matter, for one pound of sulphate of iron, 
when the former is intended to be obtained exclusively from 
galls 5 and when logwood is to be employed conjointly with 
the latter, the galls may be diminished at the rate of one half 
6f the weight of logwood. In regard to the proportion of 
galls to that of sulphate of iron, my opinion accords with that 
of Lewis, who found that three pounds of the former to one of 
the latter, commonly produced the best and most lasting 
ink. Ribaucourt, indeed, thinks two pounds of galls sufficient 
for one of sulphate of iron, and certainly with this proportion 
an ink may be produced sufficiently black ; but not so durable 
as it would be with a larger proportion of vegetable colouring 
matter. 
In regard to theus^of logwood, Chaptal does not consider 
it as being capable of adding any thing to the blackness of ink,, 
made with galls and sulphate of iron, in suitable proportions j 
but he thinks that it contributes to hinder a precipitation of 
the colouring matter, and that the ink, of which it is a com- 
ponent part, is, by its use, rendered more smooth, or marrow- 
like (moelleux) and the black in appearance more soft > and 
that 
