334 
ME. GEOEGE GOEE ON FLUOEIDE OF SILVEE. 
To ascertain the effect of a carbon vessel, a boat of Siberian graphite weighing 48 - 36 
grains was employed ; it had been partially purified in the manner already described 
(Phil. Trans. Iloy. Soc. 1870, p. 242), and was heated to incipient redness in a nearly 
closed vessel immediately before use. It contained 48-91 grains of recently fused 
argentic fluoride slightly reduced to silver by impurities in the graphite. A gentle 
current of pure iodine vapour was maintained over the red-hot salt during two hours 
in the same apparatus and manner as in the experiment with bromine (seep. 327); 
a vapour apparently heavy was evolved, which fumed in the air, and was strongly acid 
to litmus paper without first bleaching it. After expelling the excess of iodine by a red 
heat, the tube and its contents had gained 40 ’00 grains, theory requiring 41-55 grains 
if all the fluorine was expelled and the boat had suffered no loss. The sublimed iodine 
was dry, and did not fume in the air. The boat and its contents weighed 137TS grains 
=a gain of 39-91 grains; and one end of the boat was a little corroded ; the salt adhered 
to the boat, and could not be separately weighed. The platinum articles were not cor- 
roded, but *38 grain of the silver-salt had been transferred to them. By melting the 
salt out of the boat, the latter was found corroded beneath. The salt was evidently 
argentic iodide. 9- 30 grains of it fused with an excess of alkaline carbonates yielded 
4-295 grains of metallic silver, =9-345 grains of the iodide. A second portion, weighing 
36’50 grains, digested with boiling water until all soluble salt was extracted, and the 
filtered solution precipitated, gave -24 grain of argentic chloride =*212 grain of argentic 
fluoride, or -523 grain of undecomposed fluoride in the total 90 grains of residue. I 
consider that in this experiment, as in similar ones with a graphite boat in bromine 
and chlorine, the fluorine of the salt was expelled in chemical union with the carbon of 
the boat. It did not appear to me necessary to repeat this experiment with a perfectly 
purified boat. 
On adding iodine to a saturated aqueous solution of argentic fluoride the mixture 
become yellow, and evolved some heat, but no visible bubbles of gas were liberated ; by- 
adding fragments of the fluoride to the mixture and stirring, a strongly acid odour was 
ultimately evolved. The reaction Avas probably similar to those with chlorine and bro 
mine, and according to the following equation-; — 
8AgF + 81 + 4H 2 0 = 5AgI + 3AgIO + SHF + O, or 7AgI + AgI0 3 + SHF + O. 
With Hydriodic Acid .- — An aqueous solution of argentic fluoride was instantly and 
completely precipitated by a brown solution of hydriodic acid, with evolution of heat. 
With Iodic Acid . — Aqueous iodic acid produced a copious white precipitate with a 
dilute solution of argentic fluoride. 
I am now examining the substance produced by the reaction of iodine and argentic 
fluoride under the influence of heat. 
Added June 3rd, 1871. — I have since determined the chemical composition of the 
volatile substance evolved by the action of argentic fluoride and iodine at red heat. 
