ME. GEORGE GORE ON FLUORIDE OE SILVER. 
329 
effervesced freely and evolved much chlorine. The dried powder changed to a dirty 
grey colour in sunlight. I also heated 26-56 grains of the dry powder gradually to 
gentle redness in a deep platinum cup ; much effervescence occurred, and an odourless 
gas, proved to be oxygen, was evolved ; the residue was argentic bromide. The loss of 
weight was *80 grain; theory requires a loss of 1-095 grain if the reaction took place 
according to the following equation : — 
5Ag Br + 3Ag Br O, or 7Ag Br -(- Ag Br 0 ;5 = 8Ag Br + 30. 
The deficiency of loss is accounted for by the oxygen previously expelled by the heat of 
the reaction, and that expelled by the heat applied in drying the mixture. 
26-76 grains of earthy fluoride of silver was dissolved in a small amount of water in 
a deep platinum cup, an excess of bromine mixed with it, and repeatedly evaporated to 
dryness with water and an excess of bromine each time, and finally fused at a low red 
heat; the weight of argentic bromide found was 39"25 grains, theory requiring 39-39 
grains ; the deficiency was due to moisture in the fluoride. 
With Hydrobromic Acid. — An aqueous solution of fluoride of silver was instantly and 
completely precipitated by an excess of aqueous hydrobromic acid. 
With Bromic Acid. — Aqueous bromic acid produced a copious white precipitate in a 
dilute aqueous solution of argentic fluoride. 
With Iodine. — Kammerer* has already made an experiment of heating fluoride of 
silver with iodine. lie introduced iodine into a perfectly dry tube of glass along with 
a small stoppered glass tube filled with an excess of the fluoride f. 
After expelling all the air by vapour of iodine, he broke the inner tube, and heated 
the apparatus to about 70° to 80° C. ( = 158° to 176° Fahr.) for twenty-four hours. The 
contents of the glass tube were then colourless, the iodine had disappeared, and the 
glass was transparent. The tube was then opened under mercury, the gas transferred to 
a eudiometer, and rapidly absorbed by a fragment of potash. After this absorption 
no trace of silica or iodine could be found in the potash ; the oxygen (of the potash) 
displaced by the fluorine had combined either with potash or water to form peroxide of 
potassium or of hydrogen. The tube was not at all attacked. He considered he had 
isolated fluorine in this experiment, and mentioned Sir Humphry Davy’s statement that 
fluorine does not attack glass, and may be transferred over mercury. He also proposed 
to try bromine instead of iodine. 
To ascertain the effect of iodine upon argentic fluoride at moderately elevated tempe- 
ratures I made several experiments. 
A platinum cup containing 32-75 grains of pure and recently fused iodine was inverted 
within a second platinum cup, containing 34-26 grains of recently fused and still hot 
* Phil. Mag. 1863, vol. xxv. p. 213 ; Chemisches Centralblatt, August 1862, p. 523 ; Miller’s ‘ Chemistry,’ 
3rd edition, vol. ii. p. 159. 
t In all those of my preliminary experiments in which fluoride of silver was heated in contact with glass, 
serious interferences occurred ; and if the silver-salt was not thoroughly fused it contained moisture, which acted 
upon glass, and also greatly promoted the absorption of the iodine. 
2 z 2 
