245,719. Meyerhofer, A. F. Jan. 10, 1925, [Convention date]. Alkali carbonates and hydrates; ammonia; ammonium chloride; hydrochloric, nitric, phosphoric, hydrofluoboric, hydrofluosilicic, and other acids. - Sodium fluoride, obtained by heating sodium silicofluoride or borofluoride, may be reacted with calcium cyanamide to produce ammonia, soda, and calcium fluoride, the calcium fluoride being treated with sodium chloride and silicon or boron fluoride, with or without an acid, to re-form the sodium silicofluoride or borofluoride and calcium chloride, and the calcium chloride is treated with ammonia and carbon dioxide to produce ammonium chloride and calcium carbonate. The calcium carbonate is converted into calcium carbide and then into calcium cyanamide in the known manner, with liberation of carbon, and this carbon appears associated with the calcium fluoride produced from the cyanamide as above described. Carbon dioxide may therefore be obtained by calcining the fluoride and used for the production of ammonium chloride as above described. Preferably, little solvent is employed, insufficient to dissolve all the reaction products, or in some cases solvent may be dispensed with. High temperature and pressure may be employed. Specifications 219,971, 222,838, 226,490, [Class 1 (iii), Oxides &c., Metallic], 226,491, and 235,588 are referred to. The Specification as open to inspection under Sect. 91 (3) (a) includes also the following matter : Various compounds are produced by reacting upon a metal, oxide, carbonate, or salt with a complex hydrofluoric acid or materials capable of producing such acid (such as hydrofluoric acid and an oxide, fluoride or other compound of the other element) to obtain a complex fluoride, and reacting this with a salt to obtain a second complex fluoride (from which the complex acid is regenerated) and the desired compound. Preferably little solvent is used, insufficient to dissolve all the reaction products, or in some cases without any solvent. In examples, zinc oxide is reacted with hydrofluosilicic acid, the zinc silicofluoride is reacted with sodium chloride, and the sodium silicofluoride is treated with sulphuric acid to recover hydronuosilicic acid or is heated to obtain sodium fluoride and silicon fiuoride. The sodium fluoride may be reacted with calcium carbonate or oxide to obtain sodium carbonate or hydrate, in the former case carbonic acid or a bicarbonate being present if desired to facilitate the reaction which may be effected under pressure. Sodium chloride or nitrate is reacted with hyclrofluosilicic acid or with hydrofluoric acid and silicon fluoride or silica to obtain hydrochloric or nitric acid and sodium fluosilicate which may be used as above described. The calcium fluoride obtained as above described is reacted with the silicon fluoride and sulphuric acid to recover hydrofluosilicic acid. Barium silicofluoride may be obtained by treating barium fluoride with silicon fluoride; or barium chloride with calcium and silicon fluorides; or monobarium hydrogen phosphate with hydrofluosilicic acid, phosphoric acid being obtained at the same time. Barium nitrate may be obtained from barium fluoride and calcium nitrate; barium fluoride by heating barium silicofluoride; barium hydrate from barium fluoride and calcium hydrate; barium peroxide from barium hydrate or oxide and oxygen; and barium oxide and nitrogen pentoxide by heating barium nitrate. Hydrofluosilicic acid may be obtained from calcium fluoride, silicon fluoride, and sulphuric acid, or from calcium silicofluoride and sulphuric acid. Sodium carbonate and calcium silicofluoride may be obtained from calcium carbonate and sodium silicofluoride. Lead silicofluoride, obtained from lead oxide and hydrofluosilicic acid, may be reacted with arsenic acid to obtain lead arsenate and hydrofluosilicic acid. Potassium borofluoride may be obtained from potassium and boron fluorides, the potassium fluoride being reacted with calcium carbonate to obtain potassium carbonate and calcium fluoride, the latter being treated with potassium chloride and boron fluoride in presence of acid to regenerate the potassium boroffuoride. This subject-matter does not appear in the Specification as accepted.