232 On Improvements in Black Writing Ink. 



Ink, as it is usually prepared, is disposed to undergo certain 

 changes, which considerably impair its value. Of these, the three 

 following are the most important : its tendency to moulding — the 

 liability of the black matter to separate from the fluid, the ink 

 then becoming what is termed ropy — and its loss of coloui', the 

 black first changing to brown, and at length entirely disappear- 

 ing. Besides these, there are objects of minor importance to be 

 attended to in the formation of ink. Its consistence should be 

 such as to enable it to flow easily from the pen, without, on the 

 one hand, its being so hquid as to blur the paper, or, on the 

 other, so adhesive as to clog the pen and to be long in drying- 

 The shade of colour is also not to be disregai'ded ; a black, ap- 

 proaching to blue, is more agreeable to the eye than a bi'owner 

 ink ; and a degree of lustre, or glossiness, if compatible with the 

 due consistence of the fluid, tends to render the characters more 

 legible and beautiful. 



With respect to the chemical constitution of ink, I may re- 

 mark, that although, as usually prepared, it is a combination of 

 the metallic salt or oxide, with all the four vegetable principles 

 mentioned above ; yet I am inclined to believe that the last three 

 of them, so far from being essential, are the principal cause of 

 the difficulty which we meet with in the formation of a perfect 

 and durable ink. I endeavoured to prove this point by a series 

 of experiments, of which the following is a brief abstract. Hav- 

 ing prepared a cold infusion of galls, I allowed a portion of it 

 to I'emain exposed to the atmosphere, in a shallow capsule, until 

 it was covered with a thick stratum of mould ; the mould was 

 removed by filtration, and the proper proportion of sulphate of 

 iron being added to the clear fluid, a compound was formed of 

 a deep black colour, which showed no farther tendency to mould, 

 and which remained for a long time without experiencing any 

 alteration. 



Another portion of the same infusion of galls had solution of 

 isinglas added to it, until it no longer produced a precipitate ; 

 by employing the sulphate of iron, a black compound was pro- 

 duced, which, although paler than that formed from the entire 

 fluid, appeared to be a perfect and durable ink. Lastly, A por- 

 tion of the infusion, of galls was kept for some time at the boil- 

 ing temperature, by means of which, a part of its contents 



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