Werner, four hydrated chromium chlorides exist, namely the green and violet salts, CrC1 3.6H 2 O, a hydrate, CrC1 3.10H 2 O and one CrC1 3.4H 2 0.
The simplest of all pozzuolanic cements would be a mixture of pure lime and hydrated silica, but though the latter is prepared artificially for various purposes, it is too expensive to be used as a cement material.
The process goes on until a relatively small quantity of water has by instalments dissolved and hydrated the 2CaSO 4 H 2 O, and has deposited CaSO 4.2H 2 O in felted crystals forming a solid mass well cemented together.
Manganese may be estimated quantitatively by precipitation as carbonate, this salt being then converted into the oxide, Mn 3 0 4 by ignition; or by precipitation as hydrated dioxide by means of ammonia and bromine water, followed by ignition to NIn 3 0 4.
Pertantalic acid, HTaO 4, is obtained in the hydrated form as a white precipitate by adding sulphuric acid to potassium pertantalate, K 3 Ta0 5.
Sodium sulphate, Na2S04, known in the hydrated condition (with ioH 2 O) as Glauber's salt, is manufactured in large quantities for conversion into the carbonate or soda (see Alkali Manufacture).
The hydrated salt loses water on heating, and partially decomposes into hydrochloric acid and magnesium oxychlorides.
A hydrated tin trioxide, Sn03, was obtained by Spring by adding barium dioxide to a solution of stannous chloride and hydrochloric acid; the solution is dialysed, and the colloidal solution is evaporated to form a white mass of 2Sn03 H20.
The pure salt is dissolved in hot water and decomposed with ammonia to produce a slightly ammoniacal hydrated oxide; this, when ignited in platinum, leaves pure TiO 2 in the form of brownish lumps, the specific gravity of which varies from 3.9 to 4.25, according to the temperature at which it was kept in igniting.
This salt is also formed by dissolving tin in strong hydrochloric acid and allowing it to crystallize, and is industrially prepared by passing sufficiently hydrated hydrochloric acid gas over granulated tin contained in stoneware bottles and evaporating the concentrated solution produced in tin basins over granulated tin.