FIBRE, VEGETABLE 359 



The defect of all these fibres is, as it regards their use in weaving, that they break 

 the knot, and in all weaving processes the fibres require frequent joining. 



FIBRE, VEGETABLE, called also LIGNIXE (Ligneux, Fr. ; Pftanzenfaserstof, 

 Ger.), is the most abundant and general ingredient of plants, existing in all their 

 parts, the root, the leaves, the stem, the flowers, and the fruit ; amounting in the com- 

 pact wood to 97 or 98 per cent. It is obtained in a pure state by treating sawdust 

 successively with hot alcohol, water, dilute muriatic acid, and weak potash-lye, which 

 dissolve, first, the resinous ; second, the extractive and saline matters ; third, the car- 

 bonate and phosphate of lime ; and, lastly, any residuary substances. Ligneous 

 fibres, such as sawdust, powdered barks, straw, hemp, flax, linen, and cotton cloth, 

 are convertible by the action of strong sulphuric acid into a gummy substance 

 analogous to dextrine, and a sugar resembling that of the grape. 



Much attention has of late years been directed to the conversion of vegetable fibre 

 into paper. See PAPER. 



' Recognition of vegetable and animal fibres in spun and woven tissues. Kopp has 

 lately examined the chemical behaviour of animal and vegetable fibres with a view to 

 their detection in mixed fabrics. Cellulose (vegetable tissue of whatsoever origin) re- 

 sists boiling aqueous solutions of an alkali, but is readily attacked by sulphuric, nitric, 

 and hydrochloric acids. Cotton can be soaked without material injury in cold water 

 containing 5 to 10 per cent, of acid; but, if heated, the cotton is disintegrated, and 

 rapidly converted into gum and sugar. Fuming nitric acid and mixtures of concen- 

 trated sulphuric and nitric acids do not dissolve cellulose, but convert it into gun- 

 cotton. Ammonia has no action on cotton and hemp at any temperature. The cuprate 

 of ammonia, an ammoniacal solution of copper, sometimes spoken of as ' Schweitzer's 

 test,' dissolves cotton, hemp, and flax. Vegetable fibre has but little affinity for 

 artificial colours. If steeped in their solutions, it takes merely a stain, which is easily 

 removed by soap. Cellulose is not easily destroyed by chlorine or the hypochlorites. 

 If burnt, it yields no particular smell. Wool, on the other hand, resists acids, even 

 when strong and hot, but is dissolved by alkalis. As it contains sulphur, sulphide of 

 sodium is found on steeping it in soda, which gives a black precipitate with the acetate 

 of lead. Nitric acid turns it yellow. The effect of chlorine and the hypochloritcs is 

 very similar. Schweitzer's test has no action in the cold, but dissolves it when hot. 

 If burnt, it gives off the well-known smell of burnt horn. The affinity for artificial 

 colours is very great, even without the aid of mordants. Silk, if burnt, smells like 

 wool. It is attacked by strong and hot acids more readily than wool. Nitric acid 

 turns it yellow. Dilute acids have little immediate action. Alkalis dissolve it ; but, 

 as no sulphur is present, there is no formation of a sulphide, and the acetate of lead 

 does not yield a black precipitate. Dilute alkalis affect it, but without solution. 

 Ammonia has no action. In Schweitzer's test it dissolves like cotton. Its affinity 

 for colours is like that of wool. To detect cotton, hemp, flax, and jute in mixture 

 with wool and silk, boil the sample in an aqueous solution of soda containing 10 per 

 cent, of hydrate of soda. Wool and silk dissolve, while the vegetable fibres remain 

 unacted upon. The whole is thrown upon a cotton filter, and the undissolved matter 

 is then washed with hot water, and afterwards with water acidulated with 5 per cent, 

 of hydrochloric acid, to which, if the residue is black or dark-coloured, a few drops of 

 chlorine-water are added. Meantime, the original alkaline filtrate can be tested for 

 wool with the acetate of lead. If a white precipitate is formed, which dissolves on 

 stirring, silk alone is present. A black precipitate indicates wool. The nitro-peroxido 

 of sodium gives a violet colour if wool be present. If the tissue is deeply coloured 

 it may be cut up and steeped for fifteen to twenty minutes in a mixture of two 

 measures of concentrated sulphuric and one of fuming nitric acid. Wool, silk, and 

 colouring matters are destroyed, while the cellulose is converted into gun-cotton. 

 White and pale mixed tissues may be tested by their affinity for colours. Cleanse 

 and rinse thoroughly in water to remove starch and similar dressings ; boil for ten 

 minutes in water containing 2 per cent, carbonate of soda and a little soap ; then rinse 



