ME. GEOEGE GOEE ON FLUOEIDE OF SIEVES. 
327 
damp glass freely ; only traces of sublimate appeared. After the process the excess of 
bromine was expelled by heat. The short tube and its contents had gained 27*37 grains 
in weight. Neither of the tubes was visibly corroded : the long one, after being cleaned, 
had lost '5 grain, and the short one only -05 grain in weight. The boat containing the 
silver-salt was much corroded, but only where the saline matter touched it, as in similar 
experiments with chlorine; after removing nearly the whole (or 93T7 grains) of the 
saline residue, and cleaning the boat, 14*30 grains of platinum was found to have been 
removed by corrosion. The residuary salt was red, and evidently contained chemically 
combined platinum ; it also visibly contained a little metallic platinum ; soluble unde- 
composed fluoride was also present in it. The gain of weight of 27*37 grains may be 
accounted for thus: — 22*97 grains of bromine decomposed 36*46 grains of argentic 
fluoride, uniting with 31*00 grains of silver and displacing 5*455 grains of fluorine, 
which by uniting with 14*2 grains of the boat, formed 19*655 grains of tetrafluoride of 
platinum, which further united with the 53*968 grains of bromide of silver to form 
73*623 grains of a stable double salt; a further amount of 5*78 grains of bromine 
decomposed 9*17 grains of argentic fluoride, uniting with 7*80 grains of silver to form 
13*58 grains of argentic bromide, and expelling 1*37 grain of fluorine, either in the free 
state or united chemically with some of the excess of bromine — most probably the latter. 
According to this, 45*63 grains of argentic fluoride was decomposed, and 6*35 grains 
remained unchanged. I did not ascertain whether a portion of the 1*37 grain of fluorine 
was expelled in the form of hydrofluoric acid, in consequence of the presence of a very 
small amount of organic matter, which I afterwards found the ordinary bromine con- 
tained. 
In a second similar experiment with highly pure and anhydrous bromine, 26*6S grains 
of the fluoride was employed. A vapour was freely evolved, which corroded glass in the 
presence of damp air. The boat and its contents gained 11*30 grains in weight, theory 
requiring 12*81 grains if all the fluorine was expelled. The saline residue contained 
some red-brown platinum salt, and by analysis it yielded 30*67 grains of argentic 
bromide, 6*50 grains of undecomposed argentic fluoride, and 2*17 grains of metallic pla- 
tinum. The boat and short tube lost 3*12 grains by corrosion; the remaining *95 grain 
of platinum passed into solution, probably as 4 *316 grain of tetrafluoride. I consider, 
from the results of these two experiments, that bromine gradually expels a portion of 
the fluorine (probably in the form of pentafluoride of bromine) from argentic fluoride in 
platinum vessels at a red heat, whilst the remainder of the fluorine corrodes and unites 
with the platinum of the vessels to form a red salt, as it does when chlorine is employed. 
The vapour of ordinary bromine was also passed over fused argentic fluoride in a 
boat of Siberian graphite, which had been partially purified (see Phil. Trans. Roy. Soc. 
1870, p. 242) but was not heated immediately before use. The silver-salt weighed 
after fusion 47*62 grains, and was slightly reduced to metal upon its surface in con- 
sequence of impurities, or of moisture, in the boat. The boat was heated to incipient 
redness in the vapour of bromine during 1^ hour, in the same manner as in the last 
mdccclxxi. 2 z 
