J?5 Metallic Solution which forms a "Yelhiv Ink. 



In 'England, Mr. Wilkinfon has employed feveral years, 

 for fufing iron ore by coke, furnaces oF lefs height than ihofe 

 which he ufed before, and he fupplies wind by three tuyeres 

 placed at equal diftances in the circumterence of the furnace. 



XIII. On a metallic Solution, which forms a,Tellow Inky 

 that appears and Jijappears like that of Hellot. Read 

 before the French National Infiitute, by C. GlLLET- 

 Laumont, AJJociate*. 



I^OME time ago, having thrown into the fire a folulion of 

 a mixture of fulphate of copper and muriate of ammonia^ 

 where it produced very agreeable colours, fome of it fell upon 

 a piece of paper placed in the chimney, which became of 

 a briiiht yellow colour. Having taken the paper from the 

 chimney, I was much aftoniflied, fome moments after, to 

 find that it was no longer coloured : on again expofing it to 

 heat the colour reappeared, and difappeared in like manner 

 on cooling. 



I tried lately to repeat this experiment; and I obtained 

 from thefe two falts, mixed nearly in equal parts, a folution 

 of a bright yellow colour when warm, and of a beautiful 

 emerald green when cold, which at firft gave cryftals in 

 oblique prifms with rhomboidal bafes, and then blue cryftals 

 in flat o6taedra. 



This liquor and the folution of the cryftals gave a yellow 

 ink, which appeared yellow with heat, and difappeared with 

 cold, but ftill bolter with moifture. 



I obferved that thefe folutions are indebted for this pro- 

 perty only to the muriate of copper, which when employed 

 alone does not produce the fame effeft. 



On comparing this ink with that given by the muriate of 

 cobalt, known under the name of the fympathetic ink of 

 Hellot, it is feen that all thefe kinds of ink are indebted for 

 the property which they have of difappcaring, only to metallic 

 muriates, which powerfully altratl the moifture of furround- 

 ing bodies. . 



The yellow ink produced by the muriate of copper and the 

 folutions which contain it (very different from thofe which, 

 being at firft invifible, remain fixed after they have appeared) 

 gives by its colour a variety very diftinft from that of Hellot, 

 which IS of a fea green : with the latter it forms varied tints 

 of an emerald green. 



• From the Journal des Mines, No, 58. 



They 



1 



