Lime Cement

This is made of caustic lime mixed with white of egg, glue, blood, milk, or similar matters. See Parolic Cement.

The lime should be freshly burned, slaked with just enough water to make it fall to powder and still be quite dry; and then it may be kept in a closely stoppered bottle. When white of egg is used, it should be beaten as is done by cooks in making cake, etc. It may then be diluted with an equal bulk of water, and the powdered lime added until the whole, when well mixed, forms a thin paste. This is spread on strips of cloth and wrapped round the joint. Faraday tells us that this lute will bear a heat approaching to visible ignition without injury.

Rubber Cement

Dissolve 1 part of india-rubber in 2 parts of linseed-oil, by heat, and work into a stiff paste with 3 parts, or as much as sufficient, of white clay.

Water Glass Cement

A concentrated solution of silicate of soda, made into a paste with powdered glass.

Wax Lute

Beeswax melted and mixed with sufficient linseed-oil to render it pliable at a blood-heat.

Soft Cement

This is made of beeswax melted with its weight of turpentine, and colored with a little Venetian red. When cold it has the hardness of common yellow soap, but at a blood-heat it is soft and easily molded. Its great use is to make tight the joints of apparatus used for preparing gases, etc., at common temperatures.

Bottle Lute

Ordinary bottle-wax is used for closing the pores of corks and ornamenting their tops; but where it is desirable to hermetically seal a bottle containing matters which are to be kept for some time, the following preparation is to be preferred: -

Take equal parts of common resin and beeswax and enough red ochre and turpentine to bring the whole to a proper consistency. These must be melted over a fire in the following manner; and the vessel in which it is made should be capable of holding three times the quantity required, to allow ample room for boiling up. An earthenware pipkin with a handle is the best thing for the purpose, and a lid must be made of tin to fit it. The luting will be rendered more or less brittle, or elastic, as the red ochre prevails. The wax is first melted, and then the resin; the ochre is then added in small quantities, and stirred quickly with a spatula each time. When all the ochre has been added, it must be allowed to boil six or eight minutes; the turpentine is then added, and briskly stirred with the spatula, and continued boiling. There is considerable risk of the mixture taking fire. Should it do so, the lid must immediately be put on the vessel to extinguish it.

If the bottles are to be kept a very long time, a little linseed-oil added to this mixture will prevent it becoming brittle by the evaporation of the turpentine.

For making joints that are to remain tight at high temperatures, we have found nothing better than good fire-clay well beaten to a paste with water and mixed with fine clean sand. For example, in making oxygen (which is now freely used in the arts), we use a retort consisting of a small castiron pot, with a lid rudely fitted. It is of no use to grind the lid carefully into its seat, for the process is not only too troublesome, but the joint soon becomes imperfect from the oxidation of the metal. The casting is left rough, the groove in the edge of the pot is filled with clay and sand prepared as described, and the lid is forced down so that the projection is forced into the lute. Such a joint, made with moderately stiff clay, may be placed in the fire at once, and will withstand a pressure of many pounds to the square inch. A retort of this kind is the most convenient article for all kinds of distillation and gas-making at high temperatures, as it is easily put together, easily taken apart, easily changed, and easily cleaned.

It is sometimes necessary to coat glass and metal apparatus that is to be exposed to a hot fire. This prevents the burning of the one and the melting of the other.