432 On Indigo. 
It is observable that the results of Dr. Ure 
and Mr. Crum present no remarkable differ- 
ences, except in regard to hydrogen; whilst 
Dr.'Tbomson finds no hydrogen; and remark- 
able differences between his results and those 
of the other two are found in the articles 
carbone and oxygen. 
The atomic constitution of indigo by the 
above authors is as follows: 
Dr. Thomson Dr. Ure Mr. Crum 
Carbone 7 atoms......... 16 atoms......... 16 atoms 
Oxyruw? Gs do. wee ZB) do. Le. 088 SU 
Azote Pi done Laos Bi ndoiwtadseunte 1 do. 
HydrogenO do. .......+ G) adn. acho pe ve A ms: 
14 25 23 
I am inclined fo think the analysis of Mr. 
Crum as likely to be an approximation to 
the constitution of pure indigo as either of 
the other two: and I should adopt his atomic 
constitution if he would modify it so as to 
adopt my weight of the atom of azote instead 
of its double, which has somehow got into 
common reception as a substitute without any 
sufficient reason that I can find. If we adopt 
my weight for azote, Mr. Crum’s atoms will 
become 16, 2, 2, and 4; which being all 
devisible by 2, become 
8 atoms carbone 
1 atom oxygen 
1 atom azote 
2 atoms hydrogen 
r2 
