123 Dr. Schunck on the Formation of Indigo-blue, 



a decoction of woad leaves with muriatic acid and boiling, gave 

 0'7635 grm. carbonic acid and 0'1510 water. 



0^1550 grm. gave 0"4!365 grm. chloride of platinum and am- 

 monium. 



IV. 0"3675 grm.j obtained by extracting finely-chopped woad 

 leaves with warm water^ adding sugar of lead to the extract, fil- 

 tering from the green precipitate, removing the excess of lead 

 mth sulphuric acid, filtering, adding more acid, and treating the 

 flocculcut deposit which was formed in the usual manner, gave 

 08950 grm. carbonic acid and 01635 water. 



0'5715 grm. gave 0*5855 grm. chloride of platinum and am- 

 monium. 



V. 0'3640 grm., prepared in a similar manner to the last, 

 gave 09020 grm. carbonic acid and 0"1640 water. 



0"4J.<70 grm. gave 0'5070 grm. chloride of platinum and am- 

 monium. 



These numbers correspond in 100 parts to — 



In passing the eye along these numbers, it will be seen that 

 the amount of oxygen decreases progressively from II. to V., 

 while that of the other constituents increases. These two ana- 

 lyses represent, in my opinion, the composition of the two ex- 

 treme members of a series, the intermediate members of which 

 consist of mixtures or compounds of the two. A number of 

 other analyses which I made, gave results which can only be ex- 

 plained on the supposition that tliere are two bodies having the 

 same general properties which I have ascribed to iudifuscine, 

 but a different composition. Of the above analyses, the first two 

 agree tolerably well with the formula C-* H>" NO^, whereas the 

 last leads to the formula C'^H'^NO^, as the following calcula- 

 tion will show : — 



^ 



It will be seen that the two formulae differ from one another 

 by two equivalents of carbonic acid, and hence the name of 



I 



