Vitreous lavas

Numerous processes have been proposed for extracting potash from felspar, leucite, alunite, and other minerals rich in this substance, but the cost is so great that very few proposals yet made ofier promise of successful competition with the Stassfurt deposits. This is even the case with alunite, where mere calcination to 1000° drives off water and sulphuric acid, leaving water-soluble potassium sulphate, and alumina. Humphry Davy in his paper On Some Chemical Agencies of Electricity (1807), indicated in Cap. Ill, found that when water was electrolyzed in cavities contained in celestine, fluorspar, zeolite, lepidolite, basalt, vitreous lava, agate, or glass, the bases separated from the acid and accumulated about the cathode. It is therefore probable that if water with finely divided potash minerals in suspension were electrolyzed, the alkali would be separated in a convenient simple way. 

If the analyses of different glasses previously given liad not solved the question, these last two would suffice to demonstrate that all the glasses are silicates in definite proportions, or, at least, mixtures of different definite silicates, dissolved the one by tl e other.. Hence it may be inferred, that by sufficiently prolonging the time of the solidification of a vitreous mass, it would be possible to separate successively compounds more and more fusible, the alkaline base concentrating more and more in the successive residues. And hence, also, may be conceived what takes place in the solidification of lavas, which have so much analogy with the pro. ducts now under consideration, and an explanation may be given of the formation of natural crystals, so diversified as they appear in their mass. 

---