There are two different cements which go by the name of Sorel'ss: namely, the "oxychloride of zinc " and the "magnesia " cement.

(1) Oxychloride Of Zinc

A solution of chloride of zinc is prepared by dissolving zinc in hydrochloric acid, so that some metallic zinc always remains undissolved. The solution is filtered and concentrated until it has the sp. gr. 1.800. Commercial oxide of zinc is mixed with water containing 2 per cent, of nitric acid to a stiff paste, which, after being dried, is heated in crucibles to a white heat, after which it is reduced to an impalpable powder. The object of this baking is to reduce the oxide to as small a bulk as possible, in which condition it has more binding power. The powder must be kept from contact with the air, to prevent access of moisture and carbonic acid gas. On bringing together the oxide and solution of chloride of zinc, the whole solidifies in a few minutes to a very hard mass. If it is desired to retard the hardening, the zinc solution may be diluted to about 1.500-1.600 sp. gr., and the oxide of zinc may be mixed with 2 to 3 per cent, of borax or chloride of ammonium.

(2) Magnesia

This was originally prepared by Sorel, of Paris, from magnesite (chiefly native carbonate of magnesium), by making a paste with powdered magnesite, 10 to 20 per cent, of hydrochloric acid, and a sufficient quantity of water, forming the mass into bricks, then burning them at a strong heat, and finally grinding them. This yields a very hard, bright-coloured cement, which bears large dilution with sand, but is not entirely waterproof. Since the immense saline deposits at Stassfurt have been worked, this cement is prepared from kieserite (a native hydrated sulphate of magnesium), many thousand tons of which are annually obtained. Kieserite is mixed with calcium hydrate, in the proportion of two molecules of the former to one of the latter, with addition of water; the mass is formed into bricks or cakes, dried, and "burnt," and powdered. The powdered mass when moistened solidifies to a marble-like mass, which does not, however, permanently resist moisture, and is best used only in the interior of buildings.

(3) The following composition forms an excellent material for moulding or for uniting stone, etc. Mix commercial zinc white with 1/2 its bulk of fine sand, adding a solution of chloride of zinc of 126 sp. gr., and rub the whole thoroughly together in a mortar. The mixture must be applied at once, as it hardens very quickly.

Making Steam-Tight Joints with Lutes

The lutes usually employed for making steam-tight joints are composed of white lead and litharge in various proportions. See Lead. (1) A steam-tight cement which is said to be superior to the ordinary white-and-red lead cement, is obtained by mixing 6 parts of finely pulverized graphite, 3 of slaked lime, 8 of sulphate of barytes, and 7 of boiled linseed oil. These ingredients must be intimately mixed. (2) Dried and powdered clay, 6 lb.; iron filings, 1 Iby, made into a paste with boiled linseed oil; used for stopping cracks and leaks in boilers, stoves, etc. (3) Litharge in fine powder, 2 parts; very fine sand, 1; lime that has been allowed to slake spontaneously in a damp place, 1; mixed, and kept from the air; made into a paste with boiled oil, and used to mend cracks, and secure steam joints. (4) Good linseed-oil varnish ground with equal weights of white lead, oxide of manganese, and pipeclay. (5) Dry, powdered clay, 1 part; clean, sifted iron filings, 2; acetic acid, sufficient to make a paste. (6) Dry, powdered clay, 8 to 10; iron filings, free from rust, 4; peroxide of manganese, 2; sea-salt, 1; borax, 1; water, sufficient to make a paste. (7) Sulphate of baryta, 1 part; clay, 2; made up with solutions of silicate of potash, and borax; it resists a very high temperature. (8) Iron filings, free from rust, 50 parts; flowers of sulphur, 2; pulverized hydrochlorate of ammonia, 1; these substances are mixed with water or urine, so as to make a solid and homogeneous paste, which is used in the joints of steam boilers.

The lute swells, becomes very, solid, and perfectly closes the joints. (9) Iron filings, 4 parts; loam, 2; powdered sandstone, 1; made into a paste with salt water; becomes very hard on setting. (10) A thick paste, composed of silicate of soda and iron filings; the latter substance may be replaced by a mixture, in equal parts, of powdered oxide of zinc and peroxide of manganese. (11) Sand, 84 parts; Portland stone, 166; litharge, 18; pulverized glass, 0.90; red lead, 0.45; sub-oxide of lead, 0.90; the whole rubbed up with oil.

Stone

(1) Sulphur, 1 part; yellow wax, 1 part; rosin, 1 part; the sulphur and rosin are melted, and the wax is then added. It is necessary to heat the surfaces to be united; the cement is applied while still hot, and pressure is exerted till it is cold. (2) Powdered gum arabic, 2 parts; finely ground white lead, 2 parts; pulverized sugar-candy, 1 part; the three substances are placed in a small bottle with a wide mouth, a little hot water is poured on them, and the whole is stirred by a stick into a homogeneous paste. The cement must be kept in a closed vessel, and a little water may be added if it becomes dry. Before use, it must be well stirred, to prevent the white lead collecting at the bottom. It is employed for joining fragments of minerals, fossils, etc.

Turners'

(1) Melt 1 lb. resin in a pan over the fire, and when melted, add a 1/2 lb. of pitch. While these are boiling add brickdust until, by dropping a little on a cold stone, you think it hard enough. In winter it may be necessary to add a little tallow. By means of this cement, a piece of wood may be fastened to the chuck, which will hold when cool; and when the work is finished, it may be removed by a smart stroke with the tool. Any traces of the cement may be removed from the work by means of benzine. (2) The heat necessary to melt the ordinary turners' cement is liable to warp thin plates of brass, and in some cases, as for example circles of mathematical instruments that require to be graduated, this is very objectionable, in such cases plaster-of-Paris is the best cement to use. (3) 1/2 oz. rosin, 1/2 oz. pitch, 1 oz. beeswax; melted together, sufficient fine brickdust added to produce desired consistence. (4) 2 lb. rosin, 2 lb. Burgundy pitch, 2 lb. dried whiting, 2 oz. yellow wax; melted and mixed together. (5) 1/2 lb. black rosin, 1 oz. yellow wax; melted together, and poured into a tin canister.