290 Dr F. Penny on the Valuation of Indigo. 





THIRD SERIES. 









Price, 



Alkalimeter 



Ash 



Water 



SPECIMENS. 



1852. 

 ». d. 



measures 

 consumed. 



per cent. 



per cent, 



Java . . . . 



5 6 



63i- 



5-4 



4.8 



Bengal . . . . 



4 10 



5H 



7-5 



50 



J? . . . . 



4 



56 



11.0 



53 



jj i 



3 4 



45J 



140 



7-2 



}j . . . . 



1 6 



24 



44-4 



4-4 



Manilla, . . . 



3 4 



35* 



28-0 



50 



(; 



2 



261- 



50-0 



5-4 



The results in these tables clearly shew the uncertainty, 

 and in several instances the positive inaccuracy, of the com- 

 mon methods at present employed by commercial men for 

 estimating the true value of this article. The indications of 

 quality afforded by colour, fracture, texture, coppery hue 

 when rubbed, cleanliness, weight, and other characters, should 

 always, in my opinion, be confirmed by the application of a 

 simple chemical process, such as I have here described. The 

 objection, on the score of the time consumed, so strongly 

 urged against many of the other methods, is certainly not 

 chargeable against this ; for, by steeping the indigo in the 

 acid over-night, twenty or thirty samples at least could be 

 easily tested in a day, and at a trifling expense. 



I may mention that there was recently sent me for exami- 

 nation, a specimen of indigo, offered in Glasgow as refined 

 indigo, at 10s. per lb. It gave 9 per cent, of ash, and 2J per 

 cent, of moisture ; and 10 grains, when dissolved in sulphuric 

 acid, consumed 82 measures of the bichromate of potash so- 

 lution. It is in very fine powder, with a deep coppery-blue 

 colour. Assuming its quality and purity to be uniform, it 

 would unquestionably be more economical, even at the high 

 price of 10s. per lb., than much of the indigo at present sold. 

 Its tinctorial powers could be relied on ; and, from the cir- 

 cumstance of its being finely pulverized, it obviously admits 

 of being rigorously tested by the bichromate process. 



The method here proposed is open, I am well aware, to 

 some of the many objections that have been advanced against 

 the well-known chlorine process. It is quite obvious, for in- 

 stance, that unless particular care is taken in dissolving the 



