96 Mr. Crum on Indigo. [Feb. 



water, and throw it upon a filter. By continuing to wash the 

 filter with distilled water, the liquid which at first passes through 

 colourless becomes more and more blue, and alter some time, 

 all the indigo which has been changed, passes through. The 

 colourless washings must be thrown away. The blue liquid con- 

 tains the new substance in solution, and does not differ in appear- 

 ance from a solution of cerulin. On the addition of muriate of 

 potash, the new substance precipitates of a most beautiful 

 reddish-purple colour, exactly similar to the colour of the vapour 

 of indigo. Let this precipitate be thrown upon a filter, and 

 washed with distilled water, till the liquid which passes through 

 forms no longer a whitish, but a red precipitate with nitrate of 

 silver. It may then be dried. 



If instead of precipitating by means of muriate of potash, we 

 take the blue liquid which passes through the filter after all the 

 sulphuric acid has been washed away, but while it is still deeply 

 coloured, and evaporate this to dryness, we obtain the new sub- 

 stance, not purple coloured, but blue, like cerulin ; and but for 

 the difficulty of separating entirely the sulphuric acid, this would 

 be the best method of preparing it. Indeed in no other way is it 

 obtained free from saline matter. 



From the property possessed by this substance of becoming 

 purple-coloured on the addition of a salt, I have called it 

 Phenicin, from the Greek word poiwt, purple ; and, to prevent 

 circumlocution, I shall hereafter make use of this terra. 



This substance, prepared with muriate of potash, is, when 

 dry, of a brownish- black colour. Heated in a crucible, it gives 

 off a little vapour of indigo. I was at first uncertain whether this 

 might not proceed from indigo formed by the decomposition of 

 part of the phenicin by the heat ; but I shall state a fact which 

 shows that the indigo may have another source, and that it may 

 exist in a small quantity in the purple substance. After the 

 filter is washed, till the washings are very slightly blue coloured, 

 the liquid that passes through is precipitated blue, instead of red, 

 by muriate of potash, and the precipitate consists of indigo with 

 a little phenicin. Thus it appears that even indigo is, in certain 

 circumstances, capable of dissolving in water. By drying the 

 phenicin, prepared as I have stated, and redissolving it, a small 

 quantity of indigo remains; but still the phenicin yields a little 

 purple vapour when heated. 



When the purple substance is burnt, it leaves about 15 per 

 cent, of ashes, which dissolve in water, and consist of sulphate 

 and muriate of potash. 



Phenicin dissolves both in water and alcohol, and the solution 

 in both cases is blue. It is precipitated again of its original 

 purple colour by all saline substances whatever. Different salts, 

 however, possess different powers of precipitation. Thus muriate 

 of ammonia, chlorate and prussiate of potash, and muriate of 

 soda, precipitate the phenicin entirely from about 60 times their 



