484 DR GEORGE WILSON ON NEW PROCESSES FOR FLUORINE, &c. 
The processes at present in use for the separation of fluorine from silica, are 
in many respects satisfactory ; but they imply the rejection of glass apparatus, 
and the use of vessels of platina, which, from their costliness, cannot be employed 
of any considerable size, and, from their opacity, render the observation of phe- 
nomena occurring within them impossible. They are thus inadmissible for opera- 
tions where large quantities of material must be dealt with ; and to the impossi- 
bility of employing glass and porcelain vessels, must be largely attributed the 
comparatively limited extent of our information as to the distribution of fluorine. 
The following processes, which, in the meanwhile, are offered only as qualita- 
tive (although I hope to succeed in rendering the second of them quantitative), 
may be carried on in the ordinary glass and porcelain vessels of the laboratory, and 
admit of everything visible being observed. They are applicable to all siliceous 
compounds or mixtures containing fluorine, provided it be present in the form of a 
fluoride which admits of decomposition by oil of vitriol at its boiling point. The 
first stage of the process consists, in both cases, in heating the silicated fluoride 
in a flask along with strong sulphuric acid, so as to occasion the evolution of the 
fluoride of silicon, Si F,. This gas is conducted by a bent tube into water, where 
it deposits a portion of gelatinous silica; and the liquid, after filtration (which, 
however, is not essential), is treated as follows :— 
In the first process, I adopted one of Berzeius’ well-known methods for the 
isolation of silicon. The filtered liquid was neutralised with potass: and the 
resulting gelatinous precipitate of fluoride of silicon and potassium (2 Si F, +3 KF), 
after being washed, was dried, and transferred to a small metallic crucible, in 
which it was heated with potassium, so as to separate and set free the silicon, 
and convert the whole of the fluorine into fluoride of potassium. This fluoride 
was then dissolved out by water, evaporated to dryness, and treated in the ordi- 
nary way with oil of vitriol, so as to evolve hydrofiuoric acid, which could be 
made to record its evolution by the etching which its vapour occasioned on a 
plate of waxed glass, with lines written on it through the wax. 
This process is necessarily tedious, and is liable to several objections. The 
most serious of these is the impossibility of effecting the complete decomposition 
of the fluoride of silicon and potassium, by potassium, so as to liberate the whole 
of the silicon; and the risk of the latter undergoing oxidation into silica during 
the washing of the ignited mass. Accordingly, though this method gives good 
results, and has enabled me to detect fluorine in coal, in which I could not pre- 
viously detect more than the faintest traces of it, yet it almost unavoidably neces- 
sitates a loss of the element in question, and is much inferior in simplicity and 
certainty to the process which I am about to describe. 
In the second process, as in the first, the substance under examination is 
heated with oil of vitriol so as to yield fluoride of silicon, which is conducted into _ 
water. The resulting solution (with or without filtration) is neutralised with 
