1870.] 



Mr. G. Gore on Fluoride of Silver. 



235 



January 12, 1871. 



General Sir EDWARD SABINE, K.C.B., President, in the Chair. 



Prof. Benjamin Peirce (elected Foreign Member in 1852) and Col. J.T. 

 Walker, R.E., were admitted into the Society. 



The following communications were read : — 



I. " On Fluoride of Silver.— Part II." By George Gore, F.R.S. 

 Received September 22, 1870. 



(Abstract.) 



This paper contains an exhaustive account of the behaviour of argentic 

 fluoride in vessels of platinum, carbon, and various fluorides in contact 

 with chlorine, bromine, and iodine at various temperatures. When argentic 

 fluoride is completely decomposed by chlorine in platinum vessels at a red 

 heat, the reaction agrees with the following equation : 



4AgF + 4Cl + Pt=4AgCl, PtF 4 . 

 Vessels of cryolite and of fluor-spar were found incapable of retaining 

 argentic fluoride in a melted state. Other vessels were also made by melt- 

 ing and casting various mixtures of earthy fluorides at a high temperature ; 

 and although forming beautiful products, probably capable of technical 

 uses, they were not capable of retaining silver fluoride in a state of fusion. 

 Numerous vessels were also made of seventeen different fluorides by 

 moulding them in the state of clay and baking them at suitable tempera- 

 tures ; these also were found incapable of holding melted fluoride of silver. 

 Argentic fluoride was only superficially decomposed by chlorine at 60° Fahr. 

 during thirty-eight days. When heated to 230° Fahr. during fifteen days 

 in a platinum vessel in chlorine, it was very little decomposed. Chloride 

 of silver heated to fusion in a platinum vessel in chlorine corroded the 

 vessel and formed a platinum-salt, as when fluoride of silver was employed. 



An aqueous solution of argentic fluoride agitated with chlorine evolved 

 heat and set free oxygen, in accordance with the following equation : — 



8 AgF + 8 C1 + 4 H a = 5 AgCl -f 3 AgCIO + 8 HF + O, 



or 



7 AgCl + AgC10 3 + 8 HF + O. 



Dry hydrochloric acid gas completely decomposed argentic fluoride in a 

 melted state, but only acted upon it superficially at 60° Fahr. A satu- 

 rated aqueous solution of argentic fluoride was not precipitated by chloric 

 acid. 



Perfectly anhydrous fluoride of silver was only superficially decomposed 

 by contact with bromine in a platinum vessel during thirty-six days at 

 60° Fahr., or during two days at 200° Fahr. At a low red heat in vessels 

 of platinum, argentic fluoride was completely decomposed by a current 



