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Updated: May 13, 2025
The glass funnels selected for use with paper filters should have an angle as near 60° as possible, and a narrow stem about six inches in length. The filters employed should be washed filters, i.e., those which have been treated with hydrochloric and hydrofluoric acids, and which on incineration leave a very small and definitely known weight of ash, generally about .00003 gram.
Sulphurous acid, we may add, is the predominant smell in a copper-work; but arsenic acid, hydrofluoric acid, and even arseniuretted hydrogen, are not at all unfrequent. Melting the Calcined Ore. This is a totally different operation from the last: in place of roasting, it is one of fusion.
It is tested by volatilisation of the silica as silicon fluoride after solution in hydrofluoric acid, and, if the analysis has been properly conducted, the residue, after treatment with the acids and ignition, should not exceed 1 mg.
The hydrogen-fluorine combination is what passes for combustion here: the result is hydrofluoric acid, the local equivalent of water. The subsurface hydrogen is produced when the acid filters down through the rock, combines with pure metals underneath." The door at the rear of the control-cabin opened, and Juan Murillo, the seismologist, entered, followed by an assistant, who was not human.
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