244 
MR. GEORGE GORE ON FLUORIDE OF SILVER. 
filmed; the excess of silver-salt employed had made the reaction complete. The 
enclosed gas was colourless, heavy, fumed in the air, had no odour of chlorine, but a 
peculiar characteristic dusty odour very distinctly, similar to that evolved when bisul- 
phide of carbon is digested with iodine and a large excess of dry argentic fluoride. The 
gas did not attack mercury or dry glass. It was freely absorbed by purified plumbago ; 
the boat of graphite absorbed 2'88 grains of it at 60° Fahr. The retort and contents 
had gained 12-90 grains (including the 2-88 grains of gas absorbed by the boat). The 
saline residue weighed 125-62 grains=8Tl grains gain of weight=17 - 448 grains, or 
379-27 cub. centims. of effective chlorine = 9 *33 8 grains of expelled fluorine ; it contained 
undecomposed fluoride of silver freely. The boat was corroded all over its inner surface 
only, and smelt strongly of the residuary gas. By heating it nearly to redness in a 
nearly closed platinum tube during half an hour, the gas was expelled, and it lost 2-88 
grains in weight. Its final weight was 117-72 grains;=TG8 grain lost by the heating 
in chlorine. The platinum apparatus was less corroded than in previous experiments, 
owing to the more rapid absorption of the chlorine by the excess of argentic fluoride, 
and had lost only 1-33 grain =*958 grain, or 20-53 cub. centims. of chlorine rendered 
non-effective. 
The general results of this experiment may be approximately explained as follows : — 
The apparatus, when ready for heating, contained 394-5 cub. centims. or 18-406 grains 
of chlorine, and 10-5 cub. centims. (or a little less) of air, and about 117*5 grains of 
silver-salt. Of this quantity of chlorine, about *958 grain was rendered non-effective; 
the remaining 17-448 grains united with the silver of the fluoride and expelled 9-338 
grains of fluorine, which united with 1-474 grain of carbon of the boat and produced 
10-812 grains of tetrafiuoride of carbon, of which 2-88 grains was in an absorbed state 
in the boat when the gas was measured, and the remaining 7 -9 32 grains occupied about 
123 cub. centims. in the apparatus. 
To obtain a still more accurate result I employed a still larger excess of the fluoride, 
and diminished the heated platinum surface by discarding a boat and cup I had pre- 
viously employed to contain the carbon boat, and also heated a less length of the retort. 
The same boat was used; it contained 153-1 grains of the fused salt. The boat and 
contents was heated during three hours, and then cooled during 1^ hour. On opening 
the receiver under mercury about 162 cub. centims. of residuary gas ( = a loss of about 
T48 grain of carbon from the boat) was found; it contained no free chlorine. On 
applying a red heat to the outer end of the retort the gas was considerably increased in 
volume, and returned only partly to its original bulk on cooling, showing that the boat 
or its contents absorbed some of the gas. Some of the gas was transferred to a glass 
vessel over mercury ; it was colourless, clear, and did not corrode mercury or glass in 
twenty days. On taking the retort off the receiver the gas exhibited the same proper- 
ties as in the last experiment, and contained no free chlorine. The amount of sublimed 
platinum salt was now very small, only -49 grain = - 20 grain of chlorine rendered non- 
effective. The total gain of the retort and its contents was only 7' 35 grains, chiefly in 
