glucose from rags. Hydrochloric acid produces a friable
mass of "hydrocellulose," probably C12H22O11, insoluble in water, but
readily attacked by alkalis, with the production of soluble derivatives;
some dextrose is formed in the original reaction. Hydrobromic acid in
ethereal solution gives furfurane derivatives. Cold dilute acids have no
perceptible action on cellulose. The actions of such acids are an
important auxiliary to bleaching, dyeing and printing processes, but
they require careful limitation in respect of concentration and
temperature. Cellulose is extremely resistant to the action of dilute
alkalis: a 1-2% solution of sodium hydrate having little action at
temperatures up to 150 deg. hence the use of caustic soda, soda ash and
sodium silicate in bleaching processes, i.e. for the elimination of the
non-cellulose components of the raw fibres. Oxidation in acid solutions
gives compounds classed as "oxycelluloses," insoluble in water, but more
or less soluble in alkalis; continued oxidation gives formic, acetic and
carbonic acids. Oxidation in alkaline solution is more easily controlled
and limited; solutions of bleaching powder, or more generally of
alkaline hydrochlorites, receive industrial application in oxidizing the
coloured impurities of the fibre, or residues left after more or less
severe alkali treatments, leaving the cellulose practically unaffected.
This, however, is obviously a question of conditions: this group of
oxidants also oxidize to oxycellulose, and under more severe conditions
to acid products, e.g. oxalic and carbonic acids. Certain bacteria also
induce decompositions which are resolutions into ultimate products of
the lowest molecular dimensions, as hydrogen, carbon dioxide, methane,
acetic acid and butyric acid (Omeliansky) (_Handb. Techn. Mykologie_ [F.
Lafar] pp. 245-268), but generally the cellulose complex is extremely
resistant to the organic ferments. Cellulose burns with a luminous flame
to carbon dioxide and water; dry distillation gives a complicated
mixture of gaseous and liquid products and a residue of charcoal or
pseudo-carbon. Chromic acid in sulphuric acid solutions effects a
complete oxidation, i.e. combustion to water and carbonic acid.

_Ligno-celluloses._--These compounds have many of the characteristics of
the cellulose esters; they are in effect ethereal compounds of cellulose
and the quinonoid lignone complex, and the combination resists
hydrolysis by weak alkalis