Gum-dextrine, or gum substitute, is made from roasted flour. It forms, mixed with water, a gum not much inferior to gum-arabic, for which it is, as the name denotes, a substitute. It is very extensively used in many manufactures, and may be obtained of any chemist. It sometimes happens that it is too brittle after drying, and does not hold. In such case add four or five drops of glycerine to a teacupful of the dextrine in solution.

Mouth Glue (Mundleim) or Solid Cement.—This is sold by stationers in thin, flat sticks or tablets, and is used by wetting and rubbing it, chiefly for paper. It is made as follows for labels:—

Sturgeon’s bladder25
Sugar12
Water36
Carbolic acid

The sturgeon’s bladder is first dissolved, the sugar then added, also a few drops of carbolic acid, which causes it to set more firmly, and also to resist mould in dampness, induced by the presence of sugar. This cement is applicable to glass, wood, or metal. Like the following, it has the advantage of being always ready to use, and requires no boiling. If it becomes too hard to use freely, let so much of it as is required steep for a time in water. Many think, from merely dampening it in the mouth when it is hard, and using it immediately, that it is a very weak adhesive, which is a mistake. A great deal of that sold by the stationers is, however, of very inferior quality, and made with very common glue.

Mouth glue in tablets:—

Transparent glue, No. 124
Sugar13
Gum-arabic5
Water50

The glue, sugar, and gum are boiled in the water until a drop let fall on a slab hardens. It is then rolled and cut into flat cakes.

To mend or make Meerschaum Pipes.—Dissolve caseine in silicate of soda; stir into the cement fine calcined magnesia. By the addition of meerschaum powder a close imitation of meerschaum in the mass can be made.

Turkish cement of the strongest kind, and such as is used to attach gems to metal, is made as follows:—

Sturgeon’s bladder cement30
Mastic (best)2
Gum-ammoniac1
Spirits of wine10