INDUSTRIAL , USES 2 3 5 



suberized walls are stained very deeply with a solution of 

 cyanin in 50 per cent alcohol to which an equal volume of 

 glycerol has been added. Lignified walls, on the other hand, 

 are not stained under these conditions. 



INDUSTRIAL USES OF CELLULOSE AND CELLULOSE 



PRODUCTS. 



One of the industries which consumes the largest amount 

 of cellulose is that of paper manufacture. Formerly the chief 

 sources of cellulose for this purpose were cotton or hemp fibres 

 but with the increased consumption of paper other sources had 

 to be found. Although straw contains cellulose which has 

 been only slightly lignified, it is found to be unsuitable for the 

 preparation of pure cellulose, owing to the fact that it contains 

 a considerable quantity of siHca. The employment of wood as 

 a source of cellulose became possible with the discovery of 

 chemical methods of destroying the non-cellulose constituent 

 lignin, i.e. the " encrusting substances," without affecting the 

 cellulose proper. 



In the manufacture of paper from linen rags or cotton 

 waste the material is cut up, cleaned, and disintegrated by 

 boiling successively with dilute sodium carbonate and caustic 

 soda under pressure ; the fibre is then bleached with chlorine, 

 the excess being subsequently removed ; it is then treated with 

 resin, soap, and alum, and spread in thin layers and dried, 

 whereby the fibres become felted together in a peculiar manner, 

 with the formation of paper. When wood is used the " en- 

 crusting substances " may be removed by boiling with calcium 

 bisulphite, whereby the lignin remains in solution and a fairly 

 pure form of cellulose, known as sulphite cellulose, is pro- 

 duced. In the preparation of inferior quality papers there 

 is no chemical treatment of the disintegrated wood pulp ; the 

 material is, therefore, known as mechanical pulp, and paper 

 made from it gives reactions for lignocellulose. Cellulose 

 used for the preparation of filter papers is, after the ordinary 

 methods of purification, treated with hydrofluoric acid to 

 remove silica. 



