( 743 ) 
referred to above, that photo-chemical decomposition is accelerated 
by chemical sensitation only in an emulsion. 
If in the ease of preparation (7) the ether or carbon tetrachloride 
is allowed to evaporate in the dark room after exposure, then the 
bromine is liberated, which is distinctly perceptible by its smell 
and the potassium iodide starch reaction. 
Between the preparations (3), (4), (5) and (6) all intermediate 
tints from blue to red could be obtained by increase o1 decrease of 
the amount of water. 
The preparations (6) and (7) still contain a trace of adsorbed 
waiter. 
With the very rapid photo chemical decomposition already referred 
to, the preparations (1) and (2) show the violet colour anew. This 
may be accounted for by the fact that D was so small, that no 
constant equilibrium pressure was to be reached in the photo-chemical 
decomposition series. 
When the experiment was repeated a number of times, preparation 
(1) showed a different colour each time, probably through changes 
in D and the light intensity. In direct sunlight especially the yellowish 
brown colour appears; sometimes it was even blue-black through 
the silver separated out. The yellowish brown mixed colour points 
to the formation of a yellow subbromide with the ultimate products. 
Tests have been made by observing the same photo-chemical 
decomposition with weaker light intensities. Then (2) yielded a red 
colour, and (3), (4) and (5) showed a distinct shifting of the colour 
towards blue. Preparation (7) assumed a greyish green colour in 
direct sunlight. Further the red preparation rapidly developed a blue 
colour in bromine- water, which colour then entirely bleached into 
silver bromide, without my being able to observe the green sub- 
bromide with certainty. Of the green, blue, and red preparations, 
the size of the grain being the same, and free from binding sub- 
stance, the red one reacted most rapidly upon sodium thiosulphate, 
H,CrO,, HNO, and (NH,),5,O,, and especially the green preparation 
showed considerable resistance. By putting the a-subbromide in a 
neutral 10°/, sodium thiosulphate solution I was able, even by the 
light in the room, to observe distinctly a colour change through 
bluish green to blue. 
The colour sequence of series II is consequently in the case of 
subbromides : 
green, bluish green, blue, violet, red, ... yellow..... . (V) 
The silver subchlorides. In the following table the same arrange- 
ment has been observed as in the case of the subbromides. 
