their own reclaimed
rubber by the "acid" process. While several of the latter--rubber shoe
concerns controlled by the United States Rubber Company--have been
consolidated, there has been an increase in the number of rubber
manufacturers reclaiming their own rubber, since the end of the patent
litigation, so that the total number of reclaiming plants now probably
is twenty.

The first step in any process for reclaiming rubber is the grinding of
the waste, for which purpose several machines have been designed
specially, an early patent for disintegrating rubber scrap by
"subjecting it to the abrading action of grindstones" having failed to
meet with favor. The most usual chemical treatment is a bath in a
solution of sulphuric acid in lead-lined tanks. Generally heat is
employed to hasten the process, through the medium of steam, in which
case the tanks are tightly closed. The next step is the washing of the
scrap, to free it of acid and dirt, after which it is sheeted by being
run between iron rollers and hung in drying rooms. As soon as it has
become dry it is ready for sale.

In the extended litigation over the acid process patents, the points
at issue related to the strength of the acid named in the various
specifications and also to the methods of applying steam. Prof.
Charles F. Chandler, called as an expert in one case, testified that
the effects of acids, such as sulphuric or hydrochloric, upon rubber
and rubber compounds, under varying strength and temperature, had been
known at a period antedating all the patents then the basis of suits
for infringement; also that their effect upon cotton and woolen
fabrics had been equally well known. They had the same effect upon
fibers, whether the latter were combined with rubber or not, but very
strong acids would affect the rubber injuriously. The line of defense
in this case was that "no invention was required in selecting the
strength of acid; only the common sense of the manufacturer, aided by
his skill and experience, was necessary to bring about the proper
results." In support of this a factory superintendent testified that
varied stocks required skill and judgment in their treatment and more
or less variation as to the strength of acid, temperature, etc.

As to the use of steam, Prof. Henry B. Cornwall, of Princeton College,
called as an expert in another case, testified that, having put to a
test the specifications in all the patents involved, he had found it
ne