384 M. C. Lea — Combinations of Silver Chloride 



Art. XLIT. — Combinations of Silver Chloride with other Metallic 

 Chlorides ; by M. Carey Lea. 



In a series of papers lately published, 1 have expressed the 

 view that the principal and characteristic product of the action 

 of light on the silver haloids is a combination of the haloid 

 with a small proportion of its own subsalt. Such was the result 

 of my analyses, and the opinion was supported by the tendency 

 which the silver haloids were found to have to unite with 

 foreign matters, such as many dyes and other organic com- 

 pounds, showing the existence in these silver haloids of a sin- 

 gular disposition to form compounds outside the laws of atomic 

 proportion. 



This opinion finds additional support from another argument 

 and a more nearly parallel case, for it appears that silver 

 chloride (and doubtless the other silver haloids) can unite with 

 small quantities of certain other metallic chlorides. That an 

 actual combination, though one quite outside of atomic pro- 

 portion, takes place, is proved by two facts ; first, that the 

 chloride with which the silver haloid unites, though soluble 

 in water, is not removable by water; again, that the properties 

 of the haloid are markedly„changed. 



This combination with another metallic chloride furnishes a 

 much nearer parallel case to the photosalts than does the com- 

 bination with a dye. For if silver chloride is found to be capa- 

 ble of taking up a small quantity of ferric or other chloride, and 

 of retaining it so firmly that it cannot be removed by washing, 

 and only with some difficulty by HC1, we are thereby justified 

 in admitting that the silver haloid may easily form a stable 

 combination with a small proportion of its own subsalt. 



In all these compounds the tendency seems always to the 

 combination of a large proportion of the silver haloid with a 

 small one of the other substance, whether the latter is a dye, 

 another chloride, or a silver subsalt — al! show the same dis- 

 position, so that I am justified in saying that my view of the 

 nature of the photosalt is supported by the existence of many 

 analogous bodies. 



These compounds of silver chloride and other metallic chlo- 

 rides form when the silver haloid is in presence of their solu- 

 tions at the moment of its precipitation. 



AgCl with Fe^Cl z . — When to dilute HC1 is added, first, ferric 

 chloride, then solution of silver nitrate, the silver chloride 

 thrown down is not white but buff-colored. The ferric chloride 

 which has united with the silver chloride cannot be removed by 

 washing. Agitating with HC1 dissolves out part, but not all. 

 It is very interesting that this small quantity of iron pro- 



