On an Indelible Ink, and on Bistre. By JOHN MACCULLOCH, 

 M.D. F.E.S. F.L.S. and M.G. Communicated by the 

 A"thor 



DEAR SIR, Edinburgh, July 20, 1 822. 



^ JljB.perishable nature of our common ink is, as you well know 3 

 a frequent source of serious inconveniencies, particularly in 

 the case of records, which it is important to preserve, if pos- 

 sible, for ever. The cause is too well known to chemists to 

 require mention ; and they also know the processes that have 

 been recommended for the restoration of manuscripts which 

 time has rendered illegible or obscure. In a minor way, we 

 are often teased with the obliteration of our labels or memo- 

 randums of experiments, in our laboratories, where acid va- 

 pours are often let loose so as to affect the atmosphere of these 

 places. Mere damp, I need scarcely say, has the same effects 

 of rendering writing, made in common ink, brown and indis- 

 tinct ; and the same effect sometimes arises from using a bad^ 

 kind of this most indispensable substance. 



Numerous projects for an indelible ink have been brought 

 forward at different times ; but none of these are effectual 

 except where they contain powders that are exempt from the 

 operation of the destroying causes: The ancients used char- 

 coal in some form, as we have attempted to use lamp black, 

 whether in that of Chinese ink or in some other shape. This 

 is indelible, as is the ink of the cuttle fish, formerly used by 

 the ^flyf Tltg >ajAfr f - jl ' TT 1 "!"' 1 as a P amt by modern artists, 

 underthenameTf sepia. , 



But there are two objections to these powders, of Whatever 

 kind, which has hitherto prevented them from coming into 

 general use. It is necessaryVhat they should be mixed with 

 glue or gum, witHout which they will not adhere to the paper. 

 These substances, as well as the powders themselves, prevent 

 inks of this nature from flowing freely through the pen, par- 

 ticularly in warm rooms, or hot weather ; and hence the pro- 

 cess of writing becomes tedious and irritating. They have 

 another fault, of no small weight, namely, that in damp situa- 

 tions, they become mouldy, and are at length destroyed, so 

 as to permit the powders to get loose, and the writing to be 

 obscured or obliterated. 



The substance which I have sent you is free from all these 

 faults at least ; although it still labours under some defects, 

 which may perhaps prevent it from being generally introduced 

 as an ink. Yet, as it is absolutely indelible, by acids as well 

 as by time, it is worthy of attention., particularly in the case& 



jT&asiuLs 



