( 736 ) 
constant for some time, is applied to the assumed subhaloids a, 9, y..., 
in which each subsequent subhaloid is poorer in halogen than the 
preceding one, and which with the same light intensity have respec- 
tively the equilibrium pressure D,, Ds, D,,..... then we get 
Die De > Dy eine eee If D= Ds, then the photo-chemical 
equilibrium will set in with the 2 subhaloid, recognizable by the 
colour of this subhaloid, that is to say, the photo-chemical decomposition 
does continue through tbe loss of halogen, but the state of decom- 
position will not proceed beyond the # subhaloid, as long as Dz does 
not decrease. Thus first a definite colour is seen to constantly increase 
with the photo-chemical decomposition till a maximum has been 
reached, after which, sometimes after a very long exposure, a change 
of colour becomes noticeable. In the case of Dz > D > D, a blend 
of the colours of the 3 and the y subhaloid will appear. Consequently, 
by giving to D a higher or a lower value, we have it in our power 
to determine the colour sequence of the subhaloid according to (II); 
by decreasing the quantity of chemical sensitizer or by preventing 
diffusion, subhaloids richer in halogen, in the opposite case subhaloids 
poorer in halogen are obtained. 
A , 
p" (eee 
A EERE ere 
| : | | | Ee 
| oeil til 
| ' \ | 
DD A 
| | 4 KH ce A a) | Re —> 9 
Tea FF x 
The graphic representation clearly shows this. If on the abscissa 
(see fig.) at mutually equidistant points A’, B, C’,.... we indicate 
the subhaloids a, B,y,...... in equal molecular quantities, and on 
the ordinate the equilibrium pressures A'A, B'B, C'C,...., corre- 
sponding to them with a definite light intensity, then the connection 
of the points A, B, C,.... must yield a line which approaches the 
abscissa from OQ in a positive direction. If we assume now that the 
amount of one of the subhaloids, say 3, decreases in such a way 
from B both in the positive and the negative direction on the 
il : 
abscissa, that at — of the distance from £' to A' or C' there is the 
Nn 
