159 



VI. — Use of the Sulpho-Purpuric Acid, (or Red Sulphate of 

 Indigo,) in the Dyeing of Worsted and Silk. 



By Mr. Edward Haeffely, of Mulhouse. 



[Read December I4lh, 1852.] 



I TAKE the liberty of drawing the attention of the Society 

 to a new fact, demonstrated in the successful application 

 on worsted and silk of the red sulphate of indigo, (the 

 phenicine of Mr. Walter Crum.) 



This chemical compound is produced by the action of 

 sulphuric acid upon indigo, and by throwing the mixture 

 thus obtained into a large quantity of water a few minutes 

 after the contact. By this means a red-coloured precipitate 

 is formed, which, when well and thoroughly washed on a 

 filter, represents the red compound in question, a very dif- 

 ferent production from the blue sulphate of indigo in its 

 composition, properties, and as regards the shades produced 

 by it. 



I have been able to produce with this red sulphate of 

 indigo, shades superior in all respects to those obtained by 

 the employment of the indigo extract, imitating the prussian 

 blue, and likewise purple shades bearing an imitation of 

 those produced by the use of logwood and cudbear, which 

 shades, I should observe, cannot be produced from the 

 commercial indigo " carmine ;" I have been induced there- 

 fore to communicate the results of the experiments I have 

 made in this matter, and at the same time I have the 



