l application in the
production of parchment paper; unsized paper is immersed in strong acid
of the proper strength for about a minute, and then immediately rinsed
in water. The acid acts upon the surface of the paper and forms the
cellulose-sulphuric acid which remains attached to the surface. On
passing into the water this is decomposed, the acid is washed away, and
the cellulose is deposited in an amorphous form on the paper, filling up
its pores and rendering it waterproof and grease-proof. Such papers are
now largely used for packing purposes.

ACTION OF HYDROCHLORIC ACID.

Dilute hydrochloric acid of from 1 deg. to 2 deg. Tw. in strength, used in the
cold, has no action on cellulose. Cotton immersed in acids of the
strength named and then well washed in water is not materially affected
in any way, which is a feature of some value in connection with the
bleaching of cotton, where the material has to be treated at two points
in the process with weak acids. Boiling dilute hydrochloric acid of 10 deg.
Tw. disintegrates cellulose very rapidly. The product is a white very
friable powder, which if viewed under the microscope appears to be
fragments of the fibre that has been used to prepare it. The product has
the composition C{12}H{22}O{11}, and is therefore a hydrate of
cellulose, the latter having undergone hydrolysis by taking up the
elements of water according to the equation 2C{6}H{10}O{5} + H{2}O
= C{12}H{22}O{11}. By further digestion with the acid, the
hydrocellulose, as it is called, undergoes molecular change, and is
converted into dextrine. In composition hydrocellulose resembles the
product formed by the addition of sulphuric acid which has received the
name of amyloid. It differs from cellulose in containing free carboxyl,
CO, groups, while its hydroxyl groups, HO, are much more active in their
chemical reactions.

Hydrocellulose is soluble in nitric acid, 1.5 specific gravity, without
undergoing oxidation. Nitrates are formed varying in composition.

The formation of hydrocellulose has a very important bearing in woollen
manufacture. It is practically impossible to obtain wool free from
vegetable fibres, and it is often desirable to separate these vegetable
fibres. For this purpose the goods are passed into a bath of
hydrochloric acid or of weak sulphuric acid. On drying the acid converts
the cotton or vegetable fibre into hydrocellulose which, being friable
or powdery, can be easily removed, while t