184 Memoir upon the Mordants 



portion of precipitate, held in solution by excess of muriatic 



acid. 



Very pure '\hite wool, treated with the ordinary propor- 

 tioi.s of solution of tin and creanj of tartar employed in 

 dyeing scarlet was washed <i groat number of times in boil- 

 int!; waier, which carried off all the. substances combined 

 with if. These washings, collected and evaporated, afforde4 

 us the same principles we had before obtained from the 

 precipitate formed by the solution of tin and cream of tar- 

 tar; we also examined, in ihe same wav, the action of co- 

 phineal, and found no difference in the results. From 

 these facts we are to a certainty convinced, that the fine 

 scarlet colour is produced bv the wool being combined with 

 colouring matter, tartarous acid, muriatic acid, and peroxide 

 of till. But we are mistaken, if we think the bath has no 

 influence on the colour; for wool combined with the mor- 

 dants we shall presentlv mention, and dved with cochineal, 

 never take the scarlet hue unless some acid be added, which 

 causes the colour to pass from yellowish to red, and at 



. length to a bright colour. This last experiment, and some 

 others we shall relate towards the close of this memoir, 

 proved to us that the wool is not coloured yellow by the 

 combination it forms with the nitric acid in excess in the 

 solution of tin, for this wool comes oiit perfectly white 

 from all the boiiinos it undergoes with the tin, when no 

 colouring matter is employed. 



Art. 3. — Of Tarir'ites of Tin, and some other Metallic 

 Solutions. 



The prof)f;5 we have already given of the formation of 

 scarlet, appear to us so decisive, that we should not have 

 thought of increasing the number, had not the importance 

 of the question induced us to extend further our labours on 

 this subject. 



We tried upon wool, in the usual proportions for dyeing 

 scarlet, all the sulphates and muriates of antimony, bis- 

 muth, zinc, and arsenic. Some of these solutions afforded 

 very asretable colours, but very different from that we wore 

 seeking to obtain. We were more fortunate in our at- 

 tempts with the tartrite of tin obtained from tartrate of 

 potass and soda, and a highly oxidized muriate of tin. 

 This salt dissolved in muriaFic acid, and used in the opera- 

 tion of dyeing, afforded us a scarlet colour as beautifnl and 

 bright as those obtained by cream of tartar and a solution 

 of Tin. The tatlrite of tin, also, dissolved in an excess of 

 its own acid, produced very good effects; however, as this 



n)ethod 



