M. C. Lea—Chloride, Bronude and Iodide of Silver. 361 
The reactions above described will serve to show under what 
a vast variety of conditions the photosalts are formed.‘ Most 
of the methods here described represent each a whole class of 
reactions, all resulting in the same general way, and these 
classes might doubtless be largely added to. Almost any 
silver solution brought into contact with almost any reducing 
agent and then treated with HCl, gives rise to the formation of 
photochloride. Almost any chlorizing influence brought to 
bear on metallic silver, has the same result. Or when silver is 
brought into contact with almost any oxidizing agent and HCl. 
It may be said without exaggeration that the number of reac- 
tions that lead to the formation of photochloride is much larger 
than that of those leading to production of normal chloride. 
Reactions of Photochloride. 
Exposed to ordinary diffuse light all the bright shades of 
silver photochloride quickly change to purple and purple black. 
The darker shades are more slowly influenced. 
Mercurie chloride gradually changes it to a dirty white. 
_ Mercurie nitrate dissolves it easily and completely, but ap- 
parently with decomposition, as it can only be recovered as 
white chloride. 
Potassic chloride seems to be without effect. 
Potassic bromide soon converts it to a dull lilac, which at 
the end of twelve hours, showed no further change. 
In contact with potassic iodide the color instantly changes 
to blue gray; this change is produced by a quantity of iodide 
too small to dissolve even a trace of silver; the filtrate is not 
darkened by ammonium sulphide. With a larger quantity 
silver is dissolved abundantly. By acting with renewed iodide 
solution, the substance continually darkens and diminishes until 
only a few black points, barely visible, are left. 
Treated with dilute solution of potassium chlorate and HCl, 
the red substance gradually passes to pink, to flesh color, and 
finally to pure white. 
The action of heat on the photochloride is very curious; its 
tendency is generally toward redness. Specimens appearing 
quite black, are rendered distinctly purple or chocolate by heat- 
ing to 212° F. in a drying oven. Often when the substance first 
separates by addition of HCl, it is pure gray; this gray will 
often be changed to pink by simply heating to 212°. (This 
happens when a gray form is produced; if the grayness is due 
to admixed metallic silver, it is only removed by boiling with 
nitric acid.) 
The somewhat surprising change of color which is often seen 
when the crude substance is boiled with nitric acid (sometimes 
