simplest imaginable way. Tissue paper, that is, cellulose, is treated
with nitric acid in the presence of sulfuric acid. The nitration is not
carried so far as to produce the guncotton used in explosives but only
far enough to make a soluble nitrocellulose or pyroxylin. This is pulped
and mixed with half the quantity of camphor, pressed into cakes and
dried. If this mixture is put into steam-heated molds and subjected to
hydraulic pressure it takes any desired form. The process remains
essentially the same as was worked out by the Hyatt brothers in the
factory they set up in Newark in 1872 and some of their original
machines are still in use. But this protean plastic takes innumerable
forms and almost as many names. Each factory has its own secrets and
lays claim to peculiar merits. The fundamental product itself is not
patented, so trade names are copyrighted to protect the product. I have
already mentioned three, "parkesine," "xylonite" and "celluloid," and I
may add, without exhausting the list of species belonging to this genus,
"viscoloid," "lithoxyl," "fiberloid," "coraline," "eburite,"
"pulveroid," "ivorine," "pergamoid," "duroid," "ivortus," "crystalloid,"
"transparene," "litnoid," "petroid," "pasbosene," "cellonite" and
"pyralin."

Celluloid can be given any color or colors by mixing in aniline dyes or
metallic pigments. The color may be confined to the surface or to the
interior or pervade the whole. If the nitrated tissue paper is bleached
the celluloid is transparent or colorless. In that case it is necessary
to add an antacid such as urea to prevent its getting yellow or opaque.
To make it opaque and less inflammable oxides or chlorides of zinc,
aluminum, magnesium, etc., are mixed in.

Without going into the question of their variations and relative merits
we may consider the advantages of the pyroxylin plastics in general.