WHITING INK. 
5 
according to the temperature of the atmosphere^ and carefully Ink in which 
removing the mouldy pellicle, when it forms on its surface, *bten^^de- 
froin time to time, the mucilage will at length be wholly sepa- tomposcd ; 
rated from the remaining part of the infusion or decoction, and 
no subsequent production of mouldiness will then take place 
therein j and if it be afterwards passed through a fine strainer, 
and mixed with a suitable proportion of sulphate of iron and 
of gum arabic, an ink may be formed, which will be exempted 
from the defect of mouldiness. It w'as, probably, in this way 
that the ink sold in France under the name of encre de Guyot, 
was prepared ; and Dr. Tarry has, in the Ann, de Chiraie, 
tom. 74, given a receipe for preparing an ink on this principle. 
It must, however, be observed, that by this method of sepa- 
rating the mncilage from the colouring matter of the galls, a 
considerable portion of the latter will be also taken away and 
lost ; and there is room to suspect, that the remainder, by its 
having been kept so lung in a fluid state, will have suffered some 
degree of deterioration, tending to render the colour of the 
ink, when made with it, less durable. And, therefore, know- pmbably less 
ing that the mucilaginous part of the galls does not combine durable, 
with the iron and colouring matter in the formation of ink, 1 
thought it might be practicable and advantageous to separate the 
former from the latter, by adding just enough of caustic potash 
to the ink to neutralize the sulphuric acid, and throw down 
the black compound of iron and vegetable colouring matter j 
and after separating this last by a filtre, or fine strainer, re- 
dissolving, converting it again to ink with sulphuric acid, suffi- 
ciently diluted, or with distilled vinegar, avoiding that which 
had not been distilled, as it would restore other mucilage almost 
as hurtful as that which this process might separate. And, 
having produced an ink in this way, I found it quite unobjec- 
tionable, and free from all disposition to become mouldy. 
Newman formerly recommended the adding of cloves to Oil of cloves 
ink, in order to counteract its disposition to mouldiness j and 
the late Dr. Black adopted this recommendation, advising only, 
that the cloves should be powdered, and rubbed in a mortar 
with the mucilage of gum arabic, to render their essential oil 
luiKible 
