A solution of indiarubber in twice its weight of raw linseed-oil, heated, and mixed with an equal weight of pipe clay, yields a plastic mass which will long 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 sulphuric acid boils. This cement is not at all attacked by hydrochloric, and but very little by nitric acid. When heated it softens but very little. It does not easily dry upon the surface. If this cement is mixed with 1/5 of its weight of litharge, or minium, it dries up in the course of time, and becomes hard. This is known as "Benicke's Cement."
Melted indiarubber alone answers well for securing joints against chlorine and some acid vapours.
A mixture of China-clay and boiled linseed-oil, in the proportions needed to produce the right consistence.
Quicklime and linseed-oil, mixed stiffly together, form a hard cement, resisting both heat and acids.
A stiffly mixed paste of pipeclay and coal tar. A cement which, according to Dr. Wagner, is proof against even boiling acids, may be made by a composition of indiarubber, tallow, lime, and red lead. The indiarubbei must first be melted by a gentle heat, and then 6 to 8 per cent, by weight of tallow is 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.
A concentrated solution of silicate of soda, formed into a paste with powdered glass. This simple mixture will sometimes be found invaluable in the operations of the laboratory where a luting is required to resist the action of acid fumes.
1 part rosin, 1 sulphur, 2 brickdust; the whole is melted after careful mixing. This lute is proof against the attacks of nitric and hydrochloric acid vapours.
A luting which will resist acid vapours and chlorine, even at a high temperature, and is thus applicable to chlorine and hydrochloric apparatus, may be prepared by mixing three parts by weight of fine dry clay with one part by weight of the residue left from the distillation of glycerine. This mixture does not lose its plastic properties even at a high temperature, but is not suited for use where it might be exposed to atmospheric changes, since the glycerine which it contains absorbs moisture. Hence it should be prepared immediately before use.