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MB. E. HAEFFELY ON THE USE OF SULPHO-PUEPTJBIC ACID, ETC. 



I incline to the opinion that it is a modification of indigo- 

 tine, or of the acid colouring substance ; for I found that 

 this sulpho-purpuric acid, in contrariety to the opinion gene- 

 rally entertained, is an intense red-coloured compound, when 

 DRY, and not an intense blue one. 



Nevertheless, upon examining the patterns dyed with this 

 red compound, it will be found that they are blue on these 

 fabrics, and not red; and those patterns passed through 

 alkali are purple, — an effect which is not produced by 

 indigotine. 



I have not yet completely solved this question, and for 

 the present only take the liberty of calling attention to the 

 new shades obtained by the employment, in the dyeing pro- 

 cess, of this sulpho-purpuric acid, viz., the blue, imitating 

 Prussian blue, and the indigo purple, imitating the shades 

 obtained by the use of logwood. 



