4. Dissolve 20 parts of glue in an equal weight of hot water, then cautiously pour in, stirring constantly, 4 parts of strong nitric acid, warm until the nitrous fumes have been driven off, filter, if necessary, through fine shavings, and allow to cool.
5. Dissolve 3 parts of glue in small pieces in 12 to 15 parts of saccharate of lime. By heating, the glue dissolves rapidly and remains liquid, when cold, without loss of adhesive power. Any desirable consistency can be secured by varying the amount of saccharate of lime. Thick glue retains its muddy color, while a thin solution becomes clear on standing.
The saccharate of lime is prepared by dissolving 1 part of loaf sugar in 3 parts of water, and after adding one-fourth part of the weight of sugar of slaked lime, heating the whole to between 149° and 185° F., and allowing it to macerate for several days, shaking it frequently. The solution, which has the properties of mucilage, is then decanted from the sediment.
The solution of the glue in saccharate of lime is readily accomplished, even old gelatine, which has become insoluble in water, dissolving without difficulty. This variety of liquid glue possesses great adhesive power, and admits of many uses.
6. Dissolve 8 parts of glue in 16 parts of hot water, then add ½ to 1 part of hydrochloric acid, and 1½ parts of sulphate of zinc. Keep the mixture for 8 hours at 158° F., then filter through fine shavings, and allow to cool.
Steam glue. Under this name several varieties of liquid glue are brought into commerce. They are prepared as follows:—
1. Russian steam-glue. 100 parts of a good quality of glue, 100 to 110 parts of warm water, and 5.5 to 6 parts of commercial nitric acid of 36° B.
2. Pale steam-glue. 100 parts of glue, 200 of water, and 12 of nitric acid of 36° B.
3. Dark steam-glue. 100 parts of glue, 140 of water, and 16 of nitric acid of 36° B.
Soak the glue in cold water, then pour the necessary quantity of warm water over it, and heat gently on a water-bath until all the glue is dissolved. Next add gradually the nitric acid with constant stirring, and to the Russian steam-glue 6 parts of finely pulverized sulphate of lead, which will impart to it the white color.