INK. 
without materially fading or becoming il- 
legible, dries very soon after writing with 
it, and does not considerably corrode or 
soften the pen. The basis of all the com- 
mon writing inks is the fine black, or dark 
blue precipitate, formed by the addition of 
' vegetable astringents, and particularly the 
soluble part of the gall-nut, to a solution of 
iron, generally the sulphate. But as this, 
if diffused in water alone, would subside in 
a short time, and leave the supernatant li- 
quor nearly without colour, the precipitate 
is kept suspended, by thickening the water 
with gum arabic, or any other gum muci- 
lage, which also gives the ink the due con- 
sistence, and enables it to trace a fine stroke 
on the paper, without running. These ma- 
terials, therefore, that is, gall-nuts, green 
vitriol, (sulphate of iron) gum arabic, and 
water, are all that are necessary for the 
composition of ink ; and if they are of good 
quality, and properly proportioned to each 
other,^ every other addition usually made 
adds very little to its perfection. 
It is not well ascertained how soon the 
present kind of writing ink came into use. 
It has certainly been employed for many 
centuries in most European countries ; but 
the ancient Roman inks were, for the most 
part, of a totally different composition, be- 
ing made of some vegetable carbonaceous 
matter like lamp-black diffused in a liquor. 
The Chinese, and many of the inks used 
by the Oriental nations, are still of this 
kind. 
On the subject of the common writing 
ink, Dr. Lewis (“ Commerce of Arts”) has 
so fhll and so accurate an investigation, and 
his experiments are so simple and well de- 
vised, that little else can be added to the 
subject in a technical point of view. For 
a fuller chemical inquiry into the nature of 
the atramentous precipitate, the reader is 
referred to the articles Gallic Acid and 
Iron. 
Dr. Lewis first endeavoured to ascertain 
the best proportion between the galls and 
the sulphate of iron, to render the ink per- 
manent ; for it is to be observed, that with 
almost any proportions, if the entire quan- 
tity be sufficient, the ink will be fine and 
black at first, but many of these inks if 
kept for some time, especially exposed to 
light and air, will grow brown and fade, 
and the letters made with it will become 
nearly illegible. 
By trying different proportions of galls 
and sulphate of iron, it was found, that when 
about in equal quantities (the galls being 
powdered, and boiled fully to extract their 
soluble parts) they appeared to be mutually 
saturated, so that the mixed liquors would 
receive no additional blackness, from a fur- 
ther dose of one or the other. 
This, however, was only a rough approx- 
imation to accuracy, for the same effect was 
produced when either substance was also 
in a small degree superior in quantity to 
the other. But Dr. Lewis found that an 
ink, with equal parts of the two, though 
very black at first, changed to a yellowish 
brown, upon exposure to the sun and air 
only for a few days. This was again black- 
ened by washing with fresh gall infusion, 
and hence it appears in fair inference that 
the galls are a perishable substance, so that 
to insure durability, a much greater pro- 
portion must enter into the ink than is re- 
quired for mere saturation in the first in- 
stance. Thus it was found that two parts 
of galls and one of vitriol, make a much 
more durable ink than with equal parts, 
and three of galls with one of vitriol was 
still more durable. When the galls were 
increased beyond this point, the colour 
was indeed quite permanent, but it was 
not of so full a black. 
The proportion of water or other liquid 
to the solid ingredients, will admit of great 
variation. One part of vitriol, three of 
galls, and fifty parts of water, gave an ink 
black enough for common use ; but the finest 
and blackest was made when only ten of 
water were employed ; nor was any de- 
ficiency in the gallic acid observed after fif- 
teen years, though the water was scarcely 
more than sufficient to cover the galls, and 
therefore could hardly be supposed capable 
of extracting all the soluble part of them ; 
and though the vitriol from its greater so- 
lubility would probably be dissolved en- 
tirely, and thus be in greater proportion than 
usual. Other liquors besides water were 
tried. Of these, white wine and vinegar 
appeared to answer somewhat better ; but 
any considerable proportion of spirit of 
wine, or brandy, obviously did harm, owing 
to the insolubility of the sulphate of iron 
(as of all the other sulphates) in alcohol, and 
therefore its diminished solubility in any 
liquor is in proportion to the alcohol it 
contains. A decoction of logwood used in- 
stead of water sensibly improved the beauty 
of the colour. 
Instead of galls other astringents were 
employed, such as sloes, oak-bark, tormen- 
til root, &c. ; but though they all gave a 
good blue black, with the salt of iron, none 
