1823.] Mr. Crum on Indigo. 87 



proportions which form water. Hence the composition of 



indigo is 



Carbon 73-22 



Azote 11-26 



Oxygen 12-60 



Hydrogen 2-92 



100-00 

 These numbers correspond very nearly to 



1 atom of azote 1-75 or 10*77 



2 atoms of oxygen 200 12-3 1 



4 atoms of hydrogen 0*50 3*08 



16 atoms of carbon 12-00 73-84 



lti-25 100-00 



The gas remaining in the apparatus at the conclusion of the 

 experiment, was estimated by heating the same tube with an 

 equal quantity of peroxide of copper without organic matter, and 

 observing how much air was driven over into the receiver. The 

 difference between this and the whole air, as found in the sugar 

 experiment, is pretty nearly the bulk of gas remaining. The 

 temperature of the gas when measured was 58°, and the barome- 

 tric pressure 29*1 inches. 



I have also made several analyses of well-dried precipitated 

 indigo; and allowing for a minute portion of sulphate of lime 

 which it contained, 1 got results which agreed perfectly with the 

 analyses of sublimed indigo. I find too, that both these sub- 

 stances are acted upon in the same manner by other bodies. 

 The different effect of heat depends obviously, upon some differ- 

 ence in the mechanical arrangement of their particles. 



Brugnatelh has proposed to call this sublimate indigogen, 

 because, when united to the fecula of the plant, it forms common 

 indigo. But such a nomenclature is inadmissible in chemistry. 

 Upon the same principle, potash ought to be called potassogen, 

 because, when united to certain foreign substances, it forms 

 crude potash. The same chemist considers this substance as a 

 metal, because, as M. Von Mons informs us,* he found it might 

 be amalgamated with mercury. Dobereiner repeated this expe- 

 riment of Brugnatelli, and formed not only the amalgam, but 



41-55 per cent, of carbon, and in the other 4214. The mean* of these give the folio, v- 

 ing for the composition cf sugar : 



Carbon 41 H 



** ^en:::::::::::::::::::j-5 



1000 



It is needless to add that the sugar was in both cases dried at 212° in a vacuum. 

 • Annuls of Philosophy, vi. 15. 



