TRANSACTIONS OF SECTION B. 799 
According to this formula curcumine should require 4H for reduction to its leuco 
compound and 2H for conversion to the azine— 
N 
CoH(SONAK > CH80.Na) 
This latter formula would therefore represent the constitution of the pure Mikado 
orange, which dissolves in concentrated sulphuric acid with a blue colour; and, in 
agreement with this view, it has been found that 2H are required by this colour 
for reduction to the leuco compound. 
The progressive reduction is accordingly shown by the following formule :— 
O 
is pete + ee =N= 
—_—- 
+ + 
| | | | 
CH sas CH CH——_———-CH 
Curcumine Mikado orang: 
“Ae NH, 
+ = if NH, 
—p es ea 
5 jace “8 ar 
| i: | | 
Leuco compound Diamidostilbenedisulphonic acid 
(readily reoxidised in air) ; (stable in air) 
[N.B.—The crosses indicate the position of the HSO, groups.] 
The above formulz would explain the difficulty found in reducing curcumine to 
diamidostilbene disulphonic acid, also the extreme oxidisability of the leuco com- 
pound in air, a property characteristic of all azines, oxazines, thiazines, &c.; and, 
moreover, by representing these compounds as derivatives of an ortho-quinone, 
would account for their dye-stuff properties. 
It is probable that a similar constitution must be assigned to chloramine orange, 
which is formed by oxidation of diamidostilbene disulphonic acid with sodium 
hypochlorite, and to Chicago orange obtained by caustic soda condensation of 
paranitrotoluene sulphonic acid with benzidine. 
An analogous constitution is also suggested in the case of another class of 
colours—namely, the yellow, direct-dyeing, cottcn-colouring matters which are 
obtained by the oxidation of amidothiazols such as primuline and dehydrothioto- 
juidine sulphonic acid. These colouring-matters, known in commerce as oxyphenine, 
chloramine yellow, chlorophenine, &c., present great analogy with the curcumine 
colours .in their fastness to light, acids, and alkalies and in their chemical properties. 
In order to determine the amount of oxygen required for their formation pure 
dehydrothiotoluidine sulphonic acid was oxidised with a known quantity of sodium 
hypochlorite both in the cold and at 80° C. The excess of hypochlorite was deter- 
