158 



Mr. G. Gore on Fluoride of Silver. 



[Jan. 13, 



tained in the various analyses establish the fact that pure fluoride of 

 silver consists of 19 parts of fluorine and 108 of silver. 



Argentic fluoride is usually in the form of yellowish brown earthy frag- 

 ments : but when rendered perfectly anhydrous by fusion, it is a black 

 horny mass, with a superficial satin lustre, due to particles of free silver. It 

 is extremely deliquescent and soluble in water ; one part of the salt dis- 

 solves in '55 part by weight of water at i5°"5 C. : it evolves heat in dis- 

 solving, and forms a strongly alkaline solution. It is nearly insoluble in 

 absolute alcohol. The specific gravity of the earthy-brown salt is 5*852 

 at 15 c *5 C. ; the specific gravity of its aqueous solution, at 15 3 '5 C, satu- 

 rated at that temperature, is 2*61. By chilling the saturated solution, it 

 exhibited the phenomenon of supersaturation and suddenly solidified, with 

 evolution of heat, on immersing a platinum plate in it. The solution is 

 capable of being crystallized, and yields crystals of a hydrated salt ; the 

 act of crystallization is attended by the singular phenomenon of the remain- 

 der of the salt separating in the anhydrous and apparently non-crystalline 

 state, the hydrated salt taking to itself the whole of the water. The fused 

 salt, after slow and undisturbed cooling, exhibits crystalline markings upon 

 its surface. 



The dry salt is not decomposed by sunlight ; it melts below a visible 

 red heat, and forms a highly lustrous, mobile, and jet-black liquid. It is 

 not decomposed by a red heat alone ; but in the state of semifusion, or of 

 complete fusion, it is rapidly decomposed by the moisture of the air with 

 separation of metallic silver ; dry air does not decompose it. In the fused 

 state it slightly corrodes vessels of platinum, and much more freely those 

 of silver. 



The salt in a state of fusion with platinum electrodes conducts elec- 

 tricity very freely, apparently with the facility of a metal, and without 

 visible evolution of gas or corrosion of the anode ; a silver anode was 

 rapidly dissolved by it, and one of lignum-vitae charcoal was gradually cor- 

 roded. A saturated aqueous solution of the salt conducted freely with 

 electrolysis, crystals of silver being deposited upon the cathode, and a 

 black crust of peroxide of silver upon the anode ; no gas was evolved ; 

 with dilute solutions gas was evolved from the anode. By electrolysis of 

 anhydrous hydrofluoric acid with silver electrodes, the anode was rapidly 

 corroded. 



The electrical order of substances in the fused salt was as follows, 

 the first-named being the most positive : silver, platinum, charcoal of lig- 

 num-vitae, palladium, gold. In a dilute aqueous solution of the salt, the 

 order found was : aluminium, magnesium, silicon, iridium, rhodium, and 

 carbon of lignum-vitae, platinum, silver, palladium, tellurium, gold. 



The chemical behaviour of the salt was also investigated. In many 

 cases considerable destruction of the platinum vessels occurred, either in 

 the experiments themselves, or in the processes of cleaning the vessels 

 from the products of the reactions. 



