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



On reviewing these experiments, it appeared, 



1 . That chlorine, and substances readily yielding it, such as chlorides of lime 

 and antimony, totally destroy the colours of all the metallic compounds tried, 

 except one — the beautiful blue precipitate obtained on adding chloride of anti- 

 mony of the shops to the prussian alkali. This substance remains unchanged 

 when precipitated on the prepared paper B, though immersed in chlorine, oxalic 

 acid, or in diluted sulphuric, nitric, and hydrochloric acids ; but it is instantly 

 destroyed by potassa and ammonia. The intensity of the colour of this sub- 

 stance, induced me to try it as a substitute for ultramarine in oil-painting ; but 

 though its hue be exceedingly brilliant when ground with oil, I fear that it is not 

 sufficiently permanent. 



2. Oxalic acid totally effaces inks made of gallate of iron, of prussian blue, 

 of iodides of lead and mercuiy, of chromate of lead, and of sulphate of indigo ; 

 but ^vriting with this last fluid on some of the prepared papers was not wholly 

 discharged by it. 



3. Chloride of antimony destroys or weakens all the metallic inks tried, ex- 

 cept the blue antimonial one ; but writing with sulphate of indigo on paper pre- 

 pared with hydriodate of potassa is not easily effaced by this agent. 



4. The caustic alkalis weaken or destroy almost all the metallic inks, except 

 one — ^the salt formed by adding nitrate of cobalt to the prussian alkali ; but this 

 ink is effaced by chlorine and the stronger acids. 



Series VI. Mixtures of Salts of Antimony and of Cobalt. 



The mixture of the two salts of antimony and cobalt, found to be most per- 

 sistent, seemed to promise success, and became the subject of many experiments. 

 The rich golden-yellow liquid formed by mixing nitrate of cobalt and chloride of 

 antimony soon becomes solid, and gives out nitro-muriatic acid. When gi-ound 

 up with gum- water, it formed an ink, which, applied to paper prepared with 

 prussian alkali, produces dark brown letters, which, though Aveakened in colour, 

 are not destroyed by the application of an acid or an alkali ; but soaking the 

 paper first in one, and then in the other, effaces the characters entirely. 



In short, I found that none of the dark coloured salts of the metals, nor their 

 iodides, nor their sulphurets, were capable of withstanding all the chemical agents 

 tried : most of them were destructible by a single agent, and none of them were 

 capable of resisting two applied in succession. I was therefore constrained to 

 turn my attention to inks with a basis of carbon. 



The ^sXav of the Greeks, and the atramentum of the Romans, was employed 

 to denote not only writing-ink, but various carbonaceous substances used as pig- 

 ments. The ancient writing-ink, as exhibited in the Herculaneum MSS., in Egyp- 

 tian MSS. found in mummy cases, and other ancient papyri, by its qualities may 

 be proved to be carbonaceous ; even had we not the direct testimony of Vitruvius, 



