" ia a solution of silicate of potash. Without the aid of any other substance, it will securely unite fragments of stone, marble, wood, &c., and forms a valuable cement for repairing statuary. It suffices to brush the surfaces with the solution, and to press them firmly together.
Stonemasons'.—Clean river sand, 20 lb. ; litharge, 2 lb. ; quicklime, 1 lb. ; linseed oil, aufficient to form a thin paste. This cement is used for uniting fragments of stone ; after a time, it becomes exceedingly hard and strong.
Universal—Skimmed rnilk is curdled with rennet or vinegar, the whey is pressed out, and the curd is dried as quickly as posaible by a gentle heat. When quite dry, it is ground in a coffee or pepper mill, and triturated in a mortar till it is reduced to a very fine powder. This powder is mixed with 10 per cent. of new dry quicklime, also in very fine powder, and,to every ounce of this mixture, is added 5 or 6 grains of powdered camphor The whole is well triturated together, and kept in well corked, wide-mouthed bottles. When required for use, it is made into a paste with a little water, and applied immediately. It is employed to join glass, earthenware, &c.
Water, unalterable in.—(a) Good grey clay, 4 parts ; black oxide of manganese, 6 parts ; Erne. stone, reduced to powder by sprinkling it with water, 90 parts ; mixed, calcined, and powdered. (b) Manganese iron ore, 15 parte; lime, 85 parts ; calcined and powdered. Either of these cements requires to be mixed with a little sand for use; thrown into water, they harden rapidly. (c) Fine, clean sand, I cwt.; powdered quicklime, 28 lb., bone ash, 14 lb. Beaten up with water for use. (d) Quicklime, 5 parts ; fresh cheese, 6 parts ; water, 1 part. The lime is slaked by sprinkling with the water ; thereupon it is passed through a sieve, and the fresh cheese is added. The latter is prepared by curdling milk with a little vinegar, and removing the whey. The cement thus formed is very strong ; but it requires to be applied immediately, as it sets very quickly. (e) Fresh curd, as before, I part ; quicklime, 1 part ; Roman cement, 3 parte. Used for joining stone, metals, wood, &e. (f) A paste composed of hydraulic lime apd soluble glass.
Lutes. (Fs., Lut ; GER., Kitt.) A lute ia a tenacious and ductile composition, becoming solid on drying, employed to secure the joints of vessels intended to be subjected to a corrosive influence, such as heat, water, steam, acids, gases, and to prevent the escape of liquid or volatile bodies. Lutes differ in their ingredienta and modes of preparation according to the nature of bhe substance to be confined, and the degree of heat to be borne. The most useful are the following :— Acid-proof.—(a) A solution of caoutchouc in twice its weight of raw linseed oil, heated, and mixed with an equal weight of pipeclay, yields a plastic mass which will loug remain soft under cover, and never completely hardens, so that it may be easily removed at pleasure. It resists most acids and bears the heat at which aulphinic acid boils. (b) Melted caoutchouo alone will answer well for securing joints against chlorine, and some acid vapours. (c) A mixture of china-clay and boiled linseed oil, in the proportions needed to produce the right consistence. (d) Quicklime and linseed oil, mixed stiffly together, form a hard cement, resisting both heat and acids. (e) A stiffly mixed paste of pipe-clay and coal-tar. ( f ) A cement which, according to Dr. Wagner, is proof against even boiling acids, may be made by a composition of caoutchouo, tallow, lime, and red-lead. The caoutchouc must first be rnelted by a gentle heat, and then 6 to 8 per cent. by weight of tallow added to the mixture while it is kept well stirred ; next, dry slaked lime is applied, until the fluid mass assumes a. consistence similar to that of soft paste ; lastly, 20 per cent, of red-lead is added, in order to make it harden and dry. (g) A concentrated solution of silicate of soda, formed into a paste with powdered glass. (h) Rosin, 1 part ; sulphur, .1 part ; brickdust, 2 parts ; the whole is melted after careful mixing. This lute is proof against the attacks of nitric and hydrochloric acid vapours.
Algerian.—Wood-ashes, 2 parts ; lime, 3 parts ; sand, 1 part ; mixed, passed through a sieve, moistened with water and oil, and beaten up with a wooden mallet till the compound has acquired the right consistence.