It appeared that the practice in different factories had included the
use of sulphuric acid varying from a 2½ per cent. solution to the
full commercial strength of the acid, but one of the defendant
companies based their case upon their use of acid of the strength of
28° to 30° Baumé, whereas the patent they were charged with infringing
specified a strength of 66°. Their tanks were lead-lined and provided
on the interior with steam pipes running down the sides and along the
bottom, the sections at the bottom being perforated and the steam
admitted at a pressure of 75 to 80 pounds. The chemical treatment
lasted from 2½ to 4 hours.

The sulphuric acid treatment, however, is confined mainly to scrap
containing cotton fiber. Where woolen fibers occur, which is much less
frequently, their disintegration is accomplished generally by the use
of caustic soda.

In the mechanical process of reclaiming rubber, the rubber is
separated from the fiber, after the whole has been finely ground, by
means of an air blast, the method being not unlike that practiced by
furriers for separating hair and fur from bits of pelt after skins
have been finely divided. As the powdered waste comes from the blower,
the rubber falls in a heap near the machine, while the particles of
fiber, being lighter, are carried far enough away to make the
separation complete. Devulcanization in this case is effected by
exposure to live steam at a high temperature. No oil is used in the
process, the sheeting of the product being facilitated by means of hot
friction rollers.

The cost of reclaiming rubber by the acid process is less than by