
DR GEORGE WILSON ON NEW PROCESSES FOR FLUORINE, dc. 487 
hydrochloric acid and water; the product of distillation was tested by the less 
perfect potassium-process ; and the lines etched by the hydrofluoric acid were 
drawn too fine. Experience has taught my assistants that the wax should be 
spread thin, and the lines through it be made with a broad point, if a distinct 
etching is to be obtained. But, withal, the results with coal-ashes are sufficiently 
marked. 
I have further tested the sufficiency of the ammonia process in the following 
stringent way. A fossil bone from the Himalayas, which I had already ascer- 
tained to contain a fluoride, and which was full of crystals of carbonate of lime, 
was reduced to powder, and mixed with powdered glass so as to add to it excess 
of silica. It was then subjected to the ammonia process, and has yielded an 
etching as deep as the purest fluorspar could have given with oil of vitriol. 
The result is so marked, that I should recommend the deliberate addition of 
silica to bodies suspected to contain fluorine, as a provision for permitting such 
substances to be analysed in glass vessels, in which the largest quantities may be 
subjected to examination without risk of missing the element in search, or per- 
mitting it to escape. 
Five points call for further notice. 
1st, When a silicated fluoride, as I may, for the sake of brevity, call it, is distilled 
with oil of vitriol, the whole of the fluoride of silicon comes away as gas, as soon 
as the oil of vitriol has reached its boiling-point. It is not necessary, accordingly, 
to subject a body supposed to contain fluorine to any lengthened ebullition ; and, 
in the case of plant-ashes, it is desirable to arrest the boiling as soon as all the 
fluorine has been evolved, for protracted ebullition only occasions evolution of 
sulphurous acid. Besides the ultimate glass-etching, the escape of fluorine is 
rendered manifest by the appearance of a white gelatinous body in the water, 
through which the gas evolved (Si F,) is passed ; and by the production of a 
gelatinous, flocculent precipitate, when the solution of this gas is neutralised with 
potass. The coal-ashes gave all those results. 
2d, It appears exceedingly probable, that much of the silica occurring in the 
forms of quartz, chalcedony, opal, sinter, and the like, which is generally sup- 
posed to have been deposited from aqueous or alkaline solution, has owed its origin 
to the decomposition of fluoride of silicon by water, or has otherwise been related 
to fluorine as its solvent or transferring agent. This, or rather the less precise 
notion of fluorine conveying silica, has been suggested by my friend Mr A. Bry- 
son, and by Dr H. Bucuanay, E.1.C.S. 
3d, The occurrence of fluorspar in drusy cavities in greenstone, along with 
silica, as in the specimens obtained from Bishopton, on the Clyde; the similar 
occurrence of apophyllite in the cavities of trap; the association of topaz, pyc- 
nite, lepidolite, and most of the other compound fluorides, with granite, gneiss, 
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