| IX.— | Glue | 4 pounds |
|---|---|---|
| Glycerine | 8 ounces | |
| Nutgall | 3 ounces | |
| Acetic acid, 1 pound in 5 pounds of water. | ||
Ten years later this was approached by an English formula in which in place of {620} the nutgall and acetic acid, chromic and tannic acids were substituted, and a modicum of ground cork was added as a cheapener probably. Some four years later an ingenious Prussian gave out a formula in which to the glue and glycerine and tannic acid were added Marseilles soap and linseed oil. None of the above have ever had a commercial value, the nearest approach being the glue and glycerine compound used as a cover for gas tubing.
The substitutes that have really come into use generally are made either from linseed, cottonseed, or maize oil. Scores of these have been produced and thousands of dollars have been spent by promoters and owners in trying to make these gums do just what crude rubber will. A German formula which was partially successful is
| X.— | Linseed oil, in solution | 80 pounds |
|---|---|---|
| Lime-hardened rosin, in solution | 50 pounds | |
| Add to above | ||
| Sulphur | 8 pounds | |
| Linseed oil | 42 pounds | |
Add 20 pounds sulphur and heat to 375° F.
Rubber And Rubber Articles.
To prevent rubber tubes from drying up and becoming brittle, they should be coated with a 3 per cent aqueous solution of carbolic acid, which preserves them. If they have already turned stiff and brittle, they can be rendered soft and pliant again by being placed in ammonia which has been made liquid with double the amount of water.
In France rubber tubes are used as a core for casting pipes from cement and sand. In order to construct a connected pipe conduit in the ground, a groove is dug and a layer of cement mortar spread out. Upon this the rubber tube is laid, which is wrapped up in canvas and inflated. The remaining portion of the channel is then filled up with cement mortar, and as soon as it has set, the air is let out of the rubber hose and the latter is pulled out and used as before.
To cover cloth with rubber, there are chiefly employed for dissolving the rubber, naphtha, alcohol, and benzol. They are mixed with purified solid paraffine, and ground together.
Rubber boots and shoes are rendered waterproof by melting 4 parts of spermaceti and 1 part of rubber on a moderate fire, adding tallow or fat, 10 parts, and lastly 5 parts of copal varnish or amber varnish. This mixture is applied on the shoes with a brush. It should be stated that the rubber used for this purpose must be cut up very small and allowed 4 to 5 hours to dissolve.