The action of acids on cellulose is a very varied one, being dependent
upon several factors, such as the particular acid used, the strength of
the acid, duration of action, temperature, etc. As a rule, organic
acids--for example acetic, oxalic, citric, tartaric--have no action on
cellulose or cotton. Solutions of sulphuric acid or hydrochloric acid of
2 per cent. strength have practically no action in the cold, and if
after immersion the cotton or cellulose be well washed there is no
change of any kind. This is important, as in certain operations of
bleaching cotton and other vegetable fibres it is necessary to sour
them, which could not be done if acids acted on them, but it is
important to thoroughly wash the goods afterwards. When the acid
solutions are used at the boil they have a disintegrating effect on the
cellulose, the latter being converted into hydrocellulose. When dried,
the cellulose is very brittle and powdery, which in the case of cotton
yarn being so treated would show itself by the yarn becoming tender and
rotten. The degree of action varies with the temperature (the higher
this is the stronger the action), and also according to the strength of
the acid solution. Thus a 10 per cent. solution of sulphuric acid used
at a temperature of 80 deg. C. begins to act on cotton after about five
minutes' immersion, in half an hour there is a perceptible amount of
disintegration, but the complete conversion of the cotton into
hydrocellulose requires one hour's immersion. A dilute acid with 8
volumes of water, used in the cold, takes three hours' immersion before
any action on the cotton becomes evident.

ACTION OF SULPHURIC ACID ON COTTON.

When cellulose (cotton) is immersed in strong sulphuric acid the cotton
becomes gradually dissolved; as the action progresses cellulose
sulphates are formed, and some hydrolytic action takes place, with the
formation of sugar. This fact has long been known, but only recently has
it been shown that dextrose was the variety of sugar which was formed.
On diluting the strong acid solution with water there is precipitated
out the hydro or oxycelluloses that have been formed, while the
cellulose sulphates are retained in solution.

By suitable means the calcium, barium, or lead salts of these
cellulose-sulphuric acids can be prepared. Analysis of them shows that
these salts undergo hydrolysis, and lose half their sulphuric acid.

The action of strong sulphuric acid has a practica