Cellulose and Solvents.--Cellulose is soluble in certain solutions containing zinc, copper, or similar metallic salts.

Zinc chloride. Vulcanised fibre.-Ten parts of cellulose stirred into a solution of fifty parts zinc chloride in eighty parts of water, carefully heated at 80 ̊C., and subsequently evaporated on a water bath give a clear syrupy solution of cellulose. Several important commercial applications of this reaction are known. When the syrup is forced under high pressure through small tubes into alcohol, it yields a thread which hardens on expose to air. This thread when carbonised gives the carbon filament used for incandescent electric lamps. The manufacture of vulcanised sheets also depends upon this property of cellulose.

Copper oxide and ammonia. Willesden goods.-A mixture prepared by forcing air through a solution of copper oxide in ammonia dissolves cellulose readily. The strong solution is somewhat gelatinous, and when treated with acid the cellulose is reprecipitated as a white jelly-like mass, which hardens on drying.

Advantage is taken of this behaviour of cellulose in the manufacture of Willesden goods, such as roofing, and other fabrics which are thus rendered waterproof.

Cellulose and Weak Alkaline Solutions. Textile treatment.-Weak solutions of caustic soda, containing 2-3 per cent. of caustic have very little action upon cellulose even at 212° Fahrenheit.

The inertness of cellulose in this respect is of the greatest value in the textile trades, since a slight alkaline treatment removes fatty matter from the fibres or from textiles without affecting the goods.

Paper.-Solutions containing 4 to 10 per cent. of caustic soda when used for digesting vegetable fibres at high temperatures, brought about by heating in closed vessels under pressure, dissolve out non-cellulose constituents from the complex plant substance and set free the cellulose in a fibrous condition ready for paper-making.

Cellulose and Strong Alkaline Solutions. Mercerised cotton.--Strong caustic soda acts upon cellulose to produce an effect known as “Mercerisation,”

a term applied to a process for treating cotton, after the name of the inventor, Mercer. When cotton is immersed in strong caustic soda in the cold, it shrinks and becomes silky in appearance. The chemical changes are very remarkable, the soda entering into combination with the cellulose in the early stages of mercerisation, and being liberated in the later stages. Textile cotton goods are now treated on a large scale for the production of the well-known silky, lustrous mercerised fabrics.

Oxalic acid.-Cellulose heated with concentrated solutions of soda or potash and evaporated to dryness is converted into oxalic acid. On a practical scale sawdust is largely utilised for the manufacture of oxalic acid.

Cellulose and Weak Acids. Dyeing.-Acetic acid has very slight action upon cellulose either in the cold or at a high temperature. This fact is utilised commercially when textile goods are dyed and made up into coloured fabrics.

Bleaching. Mineral acids, such as hydrochloric and sulphuric, when used cold and in dilute solution, do not act rapidly upon cellulose. On account of this the operations of bleaching and dyeing can be effected readily. Additions of dilute acids to vats containing textile goods or paper pulp in a solution of chloride of lime aids the process of bleaching.

Separating cotton from wool.-Mineral acids in dilute solution act upon cellulose when heated, destroying the fibre and rendering it soft. The cellulose can then be broken and rubbed into a powder. Acids do not act upon wool in this way. Advantage is taken of this difference in behaviour to remove burrs

from wool and cotton from woollen goods when the latter are mixtures of cotton and wool, and so bring about a separation of vegetable from animal fibres.

Disintegration of Cellulose.-Mineral acids in dilute solution allowed to remain in contact with cellulose tissues under ordinary atmospheric conditions bring about a gradual disintegration of the fibre into a powdery non-fibrous condition, the substance produced being termed hydro-cellulose. Hence paper in which any traces of free acid are present slowly breaks up entirely.

Cellulose and Strong Sulphuric Acid. Glucose and alcohol.--Concentrated sulphuric acid of specific gravity 160 to 170 dissolves dry cellulose, forming a pale yellow solution which, on addition of water and prolonged boiling, yields glucose. On fermentation the glucose can be converted into alcohol.

On a commercial scale it is possible to convert certain forms of cellulose, and allied substances, such as starch, into glucose and alcohol.

Parchment paper.-Cellulose in the form of rag or wood paper passed through a bath of sulphuric acid of suitable strength is converted into parchment paper.

Cellulose and Nitric Acid.-A large number of commercial products are obtained by the action of nitric acid upon cellulose.

Gun-cotton. Cotton immersed for twenty-four hours at a low temperature of 8 to 10° C. in a solution of three parts of nitric acid (sp. gr. 1.5) and one part of sulphuric acid (sp. gr. 1.84) is converted into cellulose hexa-nitrate, commercially known as the most highly explosive gun-cotton.

The hexa-nitrate, when heated with nitric acid to 80 C., dissolves, and can be reprecipitated as a cellulose nitrate containing less nitric acid, viz., cellulose penta-nitrate, which is a less explosive gun-cotton.

Collodion. Cellulose nitrates of less complexity are formed when cellulose is heated for short periods of twenty to thirty minutes at higher temperatures with more dilute acid. These nitrates are soluble in ether-alcohol, and are of commercial value for photography as collodion pyroxyline, for surgical purposes in dressing wounds, and for making tips of matches waterproof.

Xylonite. The nitrates of cellulose, treated with alcohol-ether, acetone and other suitable solvents, and then mixed with camphor and suitable vegetable oils, yield such commercial produces as xylonite, celluloid, &c.

Artificial silk.-Nitrated cellulose, when dissolved in alcohol-ether to a syrupy solution, and forced under great pressure through small glass tubes into water, yields a solid smooth thread which can be wound up like silk on a bobbin. By subsequent treatment with ammonium sulphide, the combined nitric acid is removed, and the thread obtained possesses a fine lustre, being capable of taking any suitable dye. This is known as lustra-cellulose, or artificial silk.

Cellulose and Acetic Acid.-Cellulose is unacted upon by acetic acid even in a boiling solution, but it is converted into cellulose acetate by the use of acetic anhydride, and forms a thick viscous solution.

The acetates of cellulose can be used to replace the nitrates for many purposes, being non-explosive.

Cellulose and Carbon Bisulphide.

Viscoid.-Cellulose itself is not acted upon by carbon bisulphide, but when converted into alkali-cellulose, it may be worked up into some remarkable products.

Cellulose is treated with a solution containing 15 per cent. of caustic soda, squeezed until it holds about three times its weight of liquid. It is then shaken up in a closed vessel with about 50 per cent. of its weight of carbon bisulphide, and after three hours covered with water. A golden yellow solution is obtained. If this solution is allowed to stand it sets to a jelly, forming a hard mass of hydrated cellulose which gradually shrinks, the chemical by-products going into solution. The horny mass can be produced more quickly by heat.

The substance so obtained can be turned in a lathe for the manufacture of goods resembling ebony and xylonite. It is called viscoid.

Viscose. If the viscous solution is diluted with water, it can be used for sizing certain grades of paper, by the simple method of mixing it with the pulp in the beating engine and decomposing with sulphate of magnesia.

Smokeless gunpowder. The structureless, regenerated cellulose obtained by suitable treatment of viscose, when nitrated yields smokeless powder.

Cellulose nitrates produced in this way, as well as cellulose nitrates prepared from cellulose direct, are the principal ingredients of such explosives as cordite, ballistite, maximite, &c.

Cellulose and Ferments. Sugars. The complex celluloses which are found. as constituents of many seeds, and in cereals, possessing qualities quite distinct. from the fibrous celluloses of ordinary plant life, yield to the action of ferments, producing, for the most part, crystallisable sugars, and allied substances.

Ordinary fibrous cellulose is not susceptible to the action of ferments. Cellulose and Heat. Charcoal, acetic acid.-When certain complex celluloses, such as peat and wood, are submitted to dry distillation, valuable products are obtained, such as charcoal, wood spirit, and crude acetic acid. The utilisation of waste sawdust, wood shavings, &c., for the manufacture of these substances is now an important industry.

It is evident from this resumé of the derivatives of cellulose that many plants which may not be suitable for textile purposes or for paper-making would have some value for other industries. The chemical examination of raw fibres therefore becomes an essential and integral part of an investigation as to the utility of any plant.

The examination of raw fibres is usually carried out with one of two objects in view:

(1) The determination of suitability for papermaking, the yield of cellulose, and approximate cost of treatment.

(2) The more complete investigation into the chemical and physical properties of the fibre, as a measure of its probable value for industrial purposes, and not necessarily for paper-making alone.

Simple Analysis for Papermaking Fibre. The examination of the raw fibre in its simplest form involves digestion of a known weight of the air-dry substance in a closed vessel under pressure for a known period, the fibre being carefully washed, dried and weighed after treatment. The experimental autoclave usually consists of an upright copper cylindrical vessel, fitted with a removable lid, a safety-valve, steam-gauge, and oil cup for a thermometer. A convenient weight of fibre, cut into small lengths, is placed in the autoclave, covered with a measured volume of the chemical reagent made up to an exact strength, as experience may suggest, and heated gradually to a given pressure, which is then maintained for several hours.

The fibre may be treated in a copper or iron vessel with caustic soda (soda treatment) or by means of a solution containing bisulphite of lime and free sulphurous acid in a lead-lined copper or iron vessel (bisulphite treatment).

It is impossible to lay down a rigid scheme of treatment, as the condition of the raw fibre determines very largely the methods necessary for isolation of the cellulose.

In digesting a fibre with caustic soda, a preliminary trial will serve to show the conditions likely to give the maximum yield of cellulose with a minimum expenditure of time and chemicals. Thus 200 grammes of fibre boiled with 25 per cent. of its weight of caustic soda made up to a solution of 1.050 specific gravity, for four hours at 60 lb. pressure may be taken as a trial boil. The amount of soda not consumed by the fibre is then determined, and a second trial conducted with caustic soda just in excess of that consumed previously. Any necessary alteration in pressure and time of boiling can be determined by the general appearance of the boiled fibre.

The amount of caustic soda required for experimental as well as practical purposes is not altogether determined by measuring the active soda remaining in solution. There must be sufficient liquor to cover the fibre; this liquor must be of sufficient strength (i.e., specific gravity); so that light bulky fibres may require comparatively larger volumes of liquor.

The air-dried fibre is then bleached under suitable conditions, the amount of bleach being carefully measured, and the actual consumption determined. The conditions of treatment are by no means so rigid as the above table would appear to indicate, since the material can be boiled to give a hard strong fibre or a soft tender fibre as required, but the figures serve to illustrate the nature of the investigation.

The sulphite process requires digestion of the raw material with a solution of bisulphite of lime and free sulphurous acid in a lead-lined vessel. Small portions of liquor can be drawn off from the autoclave during the boiling operation and tested, so that the changes going on can be readily watched. In other respects the analysis closely resembles that made use of in the soda treatment.

Complete Analysis of a Fibre.-Under the scheme of investigation recommended by Cross and Bevan the analysis of a fibre should include the following details:

Moisture.-Determined by drying a weighed quantity of the fibre at 110° C., the loss in weight being calculated as moisture.

Mineral constituents.-Determined by burning a weighed quantity of fibre. to a white ash. The weight of ash obtained is a measure of the mineral constituents.

Hydrolysis. The action of caustic soda on fibre, resolving it into insoluble and soluble constituents, which is known as hydrolysis.

(a) Loss due to boiling fibre for five minutes in a solution of caustic soda containing 1 per. cent. Na,O.

(b) Loss due to boiling fibre under the same conditions for one hour instead of five minutes.

Cellulose. A weighed quantity of fibre is boiled for thirty minutes with dilute alkali containing 1 per cent. Na,O; thoroughly washed, squeezed out and exposed to the action of chlorine gas for one hour. It is then washed, thrown into a 2-per-cent. solution of sodium sulphite, which is gradually raised to the boiling-point. A small quantity of caustic soda is added (0-2 per cent. on the amount of solution) and the mixture boiled ten minutes.

The fibre is filtered off, washed with hot water, and bleached by immersion in a dilute solution of hypochlorite of soda (0.1 per cent. hypochlorite of soda). It is finally washed with water containing a little sulphurous acid, then with distilled water; squeezed, dried, and weighed.

This method gives a maximum yield of cellulose.

Mercerisation.-The fibre is soaked in a concentrated solution of caustic soda

(30 per cent. of Na,O) for one hour. It is then washed, dried and weighed. The loss of weight is carefully determined, and the action of the alkali on the fibre examined under the microscope.

Nitration. A weighed quantity of fibre dried at 100° C. is placed in a mixture of equal volumes of nitric acid (1.5 sp. gr.) and sulphuric acid (1.83 sp gr.) for one hour at the ordinary temperature. The increase in weight is noted, and the colour of the resulting product.

Carbon percentage.-A weighed quantity of the fibre is treated with chromic anhydride and sulphuric acid in a flask, and the products of the combustion which takes place carried over into a special gas apparatus for the measurement of the carbon monoxide and carbon dioxide produced. This analysis determines the exact percentage of carbon in the fibre.

Acid purification. A weighed quantity of fibre is digested in boiling acetic acid solution (containing 20 per cent. acetic acid), washed with alcohol, then with distilled water, dried and weighed. The loss in weight is taken as

a measure of impurities, and the fibre thus purified is used for determination of carbon percentage.