Crucible

A mixture of powdered clay and brickdust, made up with water, or a solution of borax. Used to join crucibles which are exposed to a strong heat. When mixed up with borax solution, the lute becomes a compact vitreous mass in the fire.

Curd

(1) Skimmed milk is curdled by the addition of vinegar or rennet, and beaten to a paste with powdered quicklime. (2) 1/2 pint skimmed milk, | pint vinegar, mixed with the whites of 5 eggs; the whole is well beaten, and sufficient quicklime is added to form a paste. These cements are used for mending glass and earthenware; they resist water, and a moderate degree of heat.

Cutlers'

This is the name given to various'kinds of cement used for fastening knives, etc, in their handles. (1) A very firm cement is made of 4 parts resin, 1 of beeswax, into which, when melted, 1 part of fine brickdust is stirred. It adheres with great firmness. (2) Take powdered resin, and mix with it a small quantity of powdered chalk, whiting, or slaked lime. Fill the hole in the handle with the mixture, heat the tang of the knife or fork, and thrust in. When cold, it will be securely fastened. (3) Take 1 lb. resin and 8 oz. sulphur, melt together, form into bars, or when cold reduce to powder; 1 part of the powder is to be mixed with 1/2 part of iron filings, brickdust or fine sand; fill the cavity of the handle with the mixture, and insert the tang, previously heated. (4) Pitch, 4 parts; resin, 4; tallow, 2; brickdust, 2. Melt the first three ingredients, and add the brickdust hot and finely powdered. (5) Chopped hair, flax, hemp or tow, mixed with powdered resin and applied as above. (6) 16 oz. rosin, 16 oz. hot whiting, 1 oz. wax. (7) 5 parts pitch, 1 wood-ashes, 1 hard tallow, melted together. (8) 4 lb. black rosin melted with 1 lb. beeswax, and 1 lb. red hot whiting added.

Dextrine

This is prepared from starch by the action of heat, diastase, or acids, and is sometimes called starch gum and British gum. As usually sold, it is a whitish, insipid powder, having a pleasant odour of cucumbers. It is soluble in cold and hot water, and in very dilute alcohol, but it is insoluble in strong alcohol and ether. In France it is largely employed by pastrycooks and confectioners, and by surgeons, as a stiffening for the splints used for fractured limbs. It has also been made up into roundish masses and sold for gum arabic. It is said to be used for " gumming " postage stamps, but careful trial convinced Phin that the best specimens in market are not equal to good gum arabic. It is cheaper, however, and for ordinary purposes is strong enough. Dextrine is easily prepared for use. It may be mixed with cold water and stirred or beaten for a few moments, when it will dissolve very completely. It may be used immediately, or it may be boiled. This latter improves it. For details of manufacture, see Spons' ' Encyclopaedia.'

Egg

A number of very cohesive cements, impervious to water and most liquids and vapours for a short time, are made by the union 'of quicklime with many of the vegetable and animal mucilages and glues. The following is said by Aiken to have been extensively employed by chemists for centuries under the name of " egg cement": - (1) Take some white of eggs with as much water, beat them well together, and sprinkle in sufficient slaked lime to make the whole up to the consistence of thin paste. This cement sets or becomes hard very quickly, and must be used at ouce. It is employed to mend earthenware, china, glass, marble, alabaster, spar ornaments, etc. Although waterproof to a certain extent, it does not resist moisture long unless it has been exposed to heat. (2) Freshly burnt plaster-of-Paris, 5 parts; freshly burnt lime, 1; white of egg, as much as may be needed. Reduce the two first ingredients to a very fine powder, and mix them well; moisten the surfaces to be united with a small quantity of white of egg, to make them adhesive; then mix the powder very rapidly with white of egg, and apply the mixture to the broken surfaces. If they are large, two persons should do this, each applying the cement to one portion.

The pieces are then firmly pressed together, and left undisturbed for several days.

Elastic

Zenker's. Indiarubber, 5 parts; chloroform, 3; dissolve and add powdered gum mastic, 1. Elastic and transparent. (2) Cut indiarubber into fine shreds and dissolve together 1 oz. of the rubber, 4 oz. of bisulphide of carbon, 2 dr. isinglass, and 1/2 oz. guttapercha; in using this, the parts to be joined must be covered with a thin coat of the solution, and be allowed to dry a few minutes; then heat to melting, place the parts together and compress until cold; this is useful for cementing leather or indiarubber. (Doubtful according to Phin). (3) Guttapercha, 1 lb.; caoutchouc, 4 oz.; pitch, 2 oz.; shellac, 1 oz.; linseed oil, 2 oz.; melt together. Must be heated when applied.

Engineers'

(1) Ground white lead is mixed with as much red lead as will give the mass the consistence of putty. (2) Equal weights of white and red lead and sufficient boiled linseed oil to produce the proper consistence. These compounds are applied by smearing them on a washer of hemp yarn, placed between metallic joints which are to be screwed up. They also answer well for luting the joints between stones, e. g. in cisterns, etc, and dry as hard as stone.

Fat

(1) Clay is dried, powdered, sifted, placed in an iron mortar, and incorporated with drying oil, added gradually, the whole being well beaten up till the mass assumes the consistence of a fine paste. It should be preserved under a coating of oil, to prevent it drying up. It resists the action of corrosive gases, but inconveniently softens by exposure to heat. (2) Plaster-of-Paris mixed with water, milk, or weak glue. Stands a dull-red heat.

French

Mix thick mucilage of gum arabic with powdered starch; a little lemon juice is sometimes added. Used by naturalists in mounting specimens; by artificial flower makers, and by confectioners to stick paper ornaments, wafers, papers, etc, on their fancy cakes.