322 
ME. GEOEG-E GOEE ON FLUOEIDE OF SILYEE. 
fluorine is accounted for by the continuous minute escape of that body during the 
heating process. Some of the excess of silver found is explained by the presence of a 
rather large amount of free silver in the original fluoride. The platinum boat and short 
tube had lost 24-94 grains by corrosion, and the outer tube had gained 15-33 grains of 
platinum by vapour of a salt of that metal having been transferred to it and decomposed 
by the heat; -80 grain of loose platinum was also found; the amount of platinum there- 
fore chemically combined in the red salt was about 8-81 grains (the analysis gave 9-046 
grains), theory requiring 9 -5 5 grains. The following explanation closely agrees with 
the results obtained. The 24-62 grains of fluoride of silver (including a little free silver, 
and containing about 3-683 grains of fluorine) gained about 6-882 grains of chlorine, 
forming therewith about 27-818 grains of argentic chloride. The 3‘683 grains of fluorine 
united with 9-551 grains of platinum to form tetrafiuoride, which united with the 
argentic chloride to form 41-052 grains of a double salt, which only very slowly evolved 
a small portion of its fluorine in a current of chlorine at a red heat*. The results of 
this experiment agree with those obtained with boats of platinum and gold in chlorine, 
in the retort-and-receiver apparatus (see Phil. Trans. Roy. Soc. 1870, p. 240). 
I heated some boats of cryolite and of fluor-spar very carefully to redness ; they all 
became full of minute cracks, and melted fluoride of silver passed freely through them. 
By melting argentic fluoride in boats of previously ignited alabaster it was completely 
decomposed. 
More than forty mixtures of the fluorides of glucinum, cerium, magnesium, calcium, 
strontium, lithium, and sodium, also cryolite and colourless fluor-spar, were made into 
boats by pouring them in a melted white-hot state into platinum boats immersed in red- 
hot gypsum, and either immersing a smaller platinum boat in the liquid and removing 
it after the mixture had solidified, to form the hollow part, or grinding out the hollow 
by the methods employed by lapidaries. Many of the cooled products formed beautiful 
enamel-looking substances, and might probably be used to form vessels for containing 
fluorides and for other technical purposes. The best mixtures were, 1st, the fluorides 
of calcium and magnesium in the proportion of their equivalent weights ; 2nd, 300 parts 
of fluoride of calcium, 6 of fluoride of magnesium, and 3 of fluoride of lithium. The 
mixtures fused at a strong red heat to a clear liquid like water. Some of the mixtures 
of the fluorides of magnesium and lithium, and of the fluoride of magnesium with cryolite 
or fluoride of strontium, yielded crystals (probably double salts) on solidifying. On 
melting argentic fluoride in any of these boats, it passed over their edges by capillary 
action. Boats were also cut out of pieces of caustic lime, and heated repeatedly to 
redness in a current of anhydrous hydrofluoric acid, but they did not become wholly 
converted into calcic fluoride. 
More than fifty boats were also made by moulding various fluorides in a state of wet 
paste and baking them : the fluorides tried were those of bismuth, copper, nickel, cobalt, 
lead, cadmium, zinc, manganese, uranium, chromium, cerium, magnesium, calcium, 
* The double salt absorbed about 11-70 grains of chlorine. See p. 321. 
