Читать книгу A Text-book of Paper-making - C. F. Cross - Страница 20

Table of Contents

—It has been already stated that cellulose occurs in nature for the most part in a form different from that in which we have hitherto considered it, viz. either combined or mixed with other substances which are of such a nature that they may be removed by a chemical process, more or less simple. One of the most characteristic of these modified celluloses constitutes the jute fibre, the isolated bast of an Indian plant, {17} which has an enormous industrial application for the coarser textile purposes. The chemistry of jute throws light on the course of lignification, the process by which cellulose is modified into wood, and in studying it in preference to wood we have the advantage of studying a simple tissue.

Like cellulose, jute dissolves in cuprammonia, and is similarly acted upon by the concentrated acids. By nitric acids it is converted into nitric ethers, which are yellow coloured, but in other respects closely resemble the pyroxylins. They are entirely soluble in acetone.

Jute differs from cellulose in the following respects: its percentage composition (excluding ash) is

C	47·0	48·0	per cent.
H	5·9	5·7	„
O	47·1	46·3	„

It is harsher to the touch, and its colour varies from grey to brown; it combines directly with the greater number of the organic colouring matters, removing them from solution, i.e., becoming dyed with them; it is coloured deep yellow by immersion in a solution of aniline sulphate; moistened with a solution of phloroglucol and afterwards with hydrochloric acid, it gives a deep red coloration; with pyrrol also in presence of hydrochloric acid it gives a deep carmine colour; it is attacked and partially converted into soluble products by a number of reagents which have no action, under similar conditions, upon cellulose. Certain of these we must consider more in detail.