(732 ) 
of the stable silver haloid could not possibly be Ag Hal, but must 
be Ag, Hal,, in which » is a figure as yet unknown. 
Quite independently of K. Scuaum I *°) have arrived at the same 
result by the explanation of a few developing phenomena in the 
case of exposed silver haloid free from binding substance. 
Let us indicate the sensitiveness to light of a substance generally 
by placing the letter / before the name of it, thus: 
lAeJ > / AgBr 
This is also applicable to the substance of the latent image, the 
a silver subhaloid : 
| Ag. Jn a> ACD 
Now the remarkable case may occur that seemingly 
l Ag) 
/(AgJ AgBr) > and 
| / AgBr 
Le. the reducibleness, which is pretty generally erroneously identified 
with sensitiveness, increases by exposure more rapidly in the case 
of iodide silver bromide than in the case of silver iodide or of silver 
bromide. 
This is to be accounted for by the circumstance that iodide silver 
bromide produces a substance of the latent image less sensitive to 
light than is yielded by siiver iodide, while at the same time this 
substance is formed more rapidly than by silver bromide, in other 
words, while at the same time iodide silver bromide is really more 
sensitive to light than silver bromide. In the most favourable case 
the latent image may consist of Ag, Br. As iodide silver bromide 
was obtained from the synthesis of the subbromide with iodine, it 
follows that the formula of the silver bihaloid must be Ag, Br, Ja. 
On the analogy of this Ag, Br, is obtained, if bromine is taken 
instead of iodine, so that the general formula of silver haloid becomes 
Ag, Haln. 
If we now assume that the photo-chemical decomposition of silver 
haloid, resp. subhaloid, again and again forms a new subhaloid, 
each time by the loss of one halogen atom, we obtain the following 
series : 
Ag, Hal, —Ag,Haly_;—AgnHal,_»— ... ~Ag,Halo—>Ag,Hal—nAg . (I) 
it being, of course, not impossible that one or more of these sub- 
haloids do not exist. 
R. Luruer*’) observed no difference between the oxidation potentials 
of the subhaloids of the latent and of the visible ‘photo-chemical 
decompositions, and therefore assumed the formation of the same 
