ME. GEORGE GORE ON FLUORIDE OF SILVER. 
235 
Y arious aqueous solutions of the salt were also electrolyzed. In two of these expe- 
riments a saturated solution, not containing free acid, in a platinum dish as the cathode, 
and a slightly immersed thick platinum wire as the anode, was electrolyzed by means of 
six large Grove’s cells. Free conduction occurred. No gas or odour was evolved. A 
thick, hard, and strongly adherent crust quickly formed upon the anode, and a rapid 
deposit of loose brilliant yellow scales of silver upon the cathode. The crystals soon 
extended upwards and united the electrodes. By still less immersion of the anode 
sufficient heat was evolved to boil the liquid and set free metallic silver. In another 
experiment with a large platinum anode suspended inside an inverted funnel of gutta 
percha to collect evolved gas, no gas was evolved and a similar crust was formed. The 
black crust, after washing with Avater, effervesced with ozone-like odour in strong nitric 
acid, and formed a deep broAvn opake solution. With strong hydrochloric acid it effer- 
vesced and evolved an odour like that of an oxide of chlorine. In concentrated sul- 
phuric acid it evolved gas and an odour of ozone. It also evoTed gas in strong aqueous 
ammonia. Probably, therefore, it was a peroxide of silver, such as occurs in the electro- 
lysis of a solution of argentic nitrate. 13 - 2 grains of it (which had been kept a long 
time in a glass bottle Avitli but little corrosive effect upon the glass, and contained scales 
of free silver) Avas heated gradually to redness in a narrovv platinum tube-retort ; much 
acid fume was evolved at first, and then a gas Avhich repeatedly reinflamed a red-hot 
charcoal splint explosively. The loss of weight Avas T9 grain. If the substance was 
peroxide of silver, Ag 2 0 2 , the loss should have been 1-7 grain. Metallic silver Avas left. 
By the electrolysis of a more dilute solution a similar crust was formed, but gas was 
also evolved at the anode. 
Anhydrous hydrofluoric acid, artificially chilled, Avas electrolyzed by means of ten 
Smee’s elements Avitli a silver anode. The acid conducted more freely than with an anode 
of palladium, and still more so than with one of gold (see Phil. Trans. Eoy. Soc. 1869, 
p. 189). The anode corroded rapidly, and became covered, first with a little black 
powder upon its edges, and then with a grey powder (probably metallic silver) Avhich 
contained only a trace of soluble silver-salt. 
The following is the order of electrical relation of several metals in the fused salt at a 
barely visible red heat, the most positive being named first : — silver, platinum, charcoal 
of lignum-vitas, palladium, gold. The silver Avas rapidly corroded and apparently dis- 
solved. The charcoal emitted much gas Avhen first immersed. Silicon could not be tried 
because it decomposes the salt rapidly, setting free silver ; it is not, however, necessarily 
electro-positive to silver on that account, for I have met with substances which are 
electro-negative to silver in argentic solutions from which they liberate silver rapidly. 
For a similar reason the base metals could not be tried. 
Magnesium Avas rather strongly electro-positive, and silver, palladium, and a rod of 
charcoal of lignum-vitee weakly positive to platinum in a saturated solution of the salt 
at 16° C. 
The following is the order of electrical relation found with a moderately dilute solu- 
