PROFESSOR TRAILL ON THE COMPOSITION OF A NEW WRITING-INK. 421 



The paper was dried, and afterwards sized in the usual manner. Characters 

 traced on A with sulphate of iron were black ; with sulphate of copper, were yel- 

 lowish-brown. 



On B, with chloride of antimony, they were of a brilliant blue, which resisted 

 chlorine, but was effaced by ammonia ; with sulphate of iron, of a dark blue ; 

 with sulphate of copper, they were of a rich brown ; with nitrate of cobalt, of a 

 deep brown, which resisted alkalis, but was effaced by chlorine. 



On C, with nitrate of silver, they quickly passed from white to brownish- 

 black. 



On D, with nitrate of silver, they were of yellowish-green. 



On E, with acetate of lead, they were of a lively yellow ; with bichloride of 

 mercury, of a bright crimson. 



On F, with acetate of lead, they were of an intense yellow. 



These methods afforded no protection against some of the chemical agents ; 

 nor did the reverse of the process prove of any utility. I since find that a me- 

 thod very similar was proposed to the French Institute, and found equally un- 

 availing. 



Series II. Metallic Sulphurets. 



Metallic sulphurets were totally discharged from paper by chlorine, and the 

 substances yielding it. No advantage was derived from precipitating the sulphu- 

 rets on the paper by sulphureted hydrogen. 



Series III. Sulphurets mingled with Common Ink. 



One proposition made to the French Institute, and vaunted as affording a 

 durable ink, is the mixture of sulphur et of lead with common ink. A repetition 

 of the process shewed the idea to be erroneous ; and mixtures of other metallic 

 sulphurets with that liquid were found to be equally useless. 



Series IV. Sulphate of Indigo. 



Sulphate of indigo has its colour destroyed by chlorine, and its above men- 

 tioned compounds ; but this sulphate, precipitated by carbonate of potassa or of 

 soda, when mixed with common ink, gave a blue fluid, which resists powerful 

 chemical agents better than common ink. This mixed ink, however, is very easily 

 effaced by chlorine. The precipitated colouring matter from sulphate of indigo 

 appears to be the basis of the blue inks, which are now much in use ; but I have 

 found none of them capable of resisting chlorine. 



Series V. Iodides of the Metals. 



None of the metallic iodides, when united with many different vehicles, af- 

 forded durable inks. 



