Another line of experimenting that is interesting, and that will yet produce good results, although so far it has not amounted to much, is in the use of cellulose. A very simple formula is of French origin and calls for the treating of cellulose with sulphuric acid, washing, drying, granulating, treating with resinate of soda—which is afterwards precipitated by sulphate of alumina—then drying and molding under pressure. As a matter of fact, the resultant mass would not be mistaken for rubber. An English formula is more like it. This consists of


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


Cellulose......... 15 pounds

Pitch............ 25 pounds

Asphalt.......... 20 pounds

Silica............ 20 pounds

Mastic........... 5 pounds

Bitumen......... 5 pounds

Rosin............ 10 pounds

Coal tar.......... 12 pounds

This makes a thick gummy varnish which is of little use except as for its waterproof qualities. Allen's formula for a cellulose substitute might have a value if it were carried further. It is made up of 100 pounds of rosinous wood pulp treated with animal gelatin, 100 pounds asphalt, and 10 pounds asphalt oil, all heated and molded.

The Greening process, which is English, is more elaborate than Allen's, but seems a bit laborious and costly. This process calls for the treatment of the cellulose by a mixture of sulphuric acid and nitrate of potash, and, after drying, a treatment to a bath of liquid carbonic acid. When dry again, it is mixed in a retort with refined rosin, gum benzoin, castor oil, and methylated alcohol. The distillate from this is dried by redistilling over anhydrous lime.

Another curious line of substitutes is that based upon the use of glue and glycerine. Some of these have uses, while others, that look very attractive, are of no use at all, for the simple reason that they will absorb water almost as readily as a dry sponge. The first of these is more than 30 years old and is said to be of French origin. The formula is: 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


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° P.