Cellulose is produced from lignocellulosic material by heating the material with a homogeneous mixture of (1) a halogenated organic compound (other than a chlorinated lower fatty acid) containing aliphatically bound halogen and also oxygen or sulphur, and (2) an organic diluent for the halogenated compound. The halogenated compound preferably has the formula X.R.Y.R1, where X represents chlorine or bromine, Y represents oxygen or sulphur, R is a hydrocarbon radical such that the link X-R is aliphatic in nature, and R1 represents hydrogen, a monovalent hydrocarbon group, a divalent hydrocarbon group bound by the second valency to R, or an acyl group. More particularly preferred are chlorhydrins (i.e. compounds containing one or more aliphatically-bound chlorine atoms and one or more aliphatically bound hydroxyl groups) and chlorinated mercaptans, especially such as contain 2 or 3 carbon atoms in the molecule; esters of the chlorhydrins, particularly with lower fatty acids; ethers and thioethers derived from the chlorhydrins and mercaptans, especially lower alkyl and chlorinated lower alkyl ethers and thioethers; chlorinated epoxides and chlorinated saturated and unsaturated cyclic ethers and thioethers. The term "lower fatty acid" denotes fatty acids containing 2-4 carbon atoms in the molecule, and the term "lower alkyl" denotes alkyl groups containing 1-4 carbon atoms. The halogenated compounds are best employed diluted with lower fatty acids, especially acetic acid. Other diluents may, however, be employed, e.g. aromatic or other saturated hydrocarbons such as ethyl benzene and the xylenes, normally liquid nitro-and halogeno-aromatic hydrocarbons, and fatty acid esters boiling above 110 DEG C. More volatile diluents such as ethyl acetate, acetone or chloroform may be used, but less conveniently. The proportion of diluent may be about 15-65 per cent and especially 25-45 per cent of the weight of the mixture. Mineral acids and water are preferably absent. Particularly good results are given by mixtures of ethylene chlorhydrin, 2-chloro-ethyl acetate, or epichlorhydrin with a lower fatty acid, especially acetic acid, or with xylenes or other hydrocarbons of similar boiling range. Other examples of halogenated compounds which may be used, diluted preferably with lower fatty acids, are 1- and 2-glycerol chlorhydrins, 1-chloro-2-hydroxy-propane, and 1-hydroxy-2,3-dichloropropane; methyl, ethyl, and 2-chloro - ethyl ethers of those chlorhydrins; 2 - chloro - ethyl mercaptan and 2 - chloro - ethyl methyl sulphide; 2 - chloro - furan (under pressure), 2,3-dichloro-1,4-dioxane, and 2 - chloro - thiophene. The lignocellulosic material may be cereal straws and particularly woods such as spruce, larch, pine, fir, poplar, beech and eucalyptus. After the treatment of the lignocellulosic material the cellulose produced may be filtered off and washed, preferably either with further quantities of the diluent, e.g. acetic acid, or with a more volatile solvent for the halogenated compound, e.g. acetone, or with xylene followed by acetone. If the cellulose has been washed with acetic acid it is washed free from acid with water. The washed cellulose may be bleached and whether bleached or unbleached, may be further refined by treatment with a warm solution containing 15-22 grams of caustic soda per 100 c.c. of water, as described in Specifications 640,490 and 679,832. In an example eucalyptus chips are boiled under a reflux with a mixture of equal parts by weight of ethylene chlorhydrin and glacial acetic acid. The cellulose produced is filtered off, washed with acetic acid, bleached, washed again and treated with warm 18 per cent by weight aqueous caustic soda solution to reduce its pentosan content. The filtrate and washings are either mixed with water to precipitate the lignin and treated to recover the halogenated compounds present, or re-used for treating further wood after fortifying with acetic acid. In other examples wood chips are similarly treated with mixtures of epichlorhydrin and glacial acetic acid, epichlorhydrin and xylene, and 2-chloro-ethyl acetate and glacial acetic acid, respectively. Specification 679,833 also is referred to.ALSO:Lignin is recovered from lignocellulosic material by heating the material with a homogeneous mixture of (1) a halogenated organic compound (other than a chlorinated lower fatty acid) containing aliphatically bound halogen and also oxygen or sulphur, and (2) an organic diluent for the halogenated compound. The halogenated compound preferably has the formula X.R.Y.R1, where X represents chlorine or bromine, Y represents oxygen or sulphur, R is a hydrocarbon radical such that the link X-R is aliphatic in nature, and R1 represents hydrogen, a monovalent hydrocarbon group, divalent hydrocarbon group bound by the second valency to R, or an acyl group. More particularly preferred are chlorohydrins (i.e. compounds containing one or more aliphatically bound chlorine atoms and one or more aliphatically bound hydroxyl groups) and chlorinated mercaptans, especially such as contain 2 or 3 carbon atoms in the molecule; esters of the chlorhydrins, particularly with lower fatty acids; ethers and thio-ethers derived from the chlorhydrins and mercaptans, especially alkyl and chlorinated lower alkyl ethers and thioethers; chlorinated lower alkyl ethers and thioethers; chlorinated epoxides and chlorinated saturated and unsaturated cyclic ethers and thioethers. The term "lower fatty acid" denotes fatty acids containing 2-4 carbon atoms in the molecule and the term "lower alkyl" denotes alkyl groups containing 1-4 carbon atoms. Corresponding bromine compounds can also be used. The halogenated compounds are best employed diluted with lower fatty acids, especially acetic acid. Other diluents may, however, be employed, e.g. aromatic or other saturated hydrocarbons such as ethyl benzene and the xylenes, normally liquid nitro- and halogeno-aromatic hydrocarbons, and fatty acid esters boiling above 110 DEG C. More volatile diluents such as ethyl acetate, acetone or chloroform may be used, but less conveniently. The proportion of diluent may be about 15-65 per cent and especially about 25-45 per cent of the weight of the mixture. Mineral acids and water are preferably absent from the mixture. Particularly good results are given by mixtures of ethylene chlorhydrin, 2-chloro-ethyl acetate, or epichlorhydrin with a lower fatty acid, especially acetic acid, or with xylenes or other hydrocarbons of similar boiling range. Alternatively there may be used (diluted preferably with lower fatty acids), 1- and 2-glycerol chlorhydrins, 1 - chloro - 2 - hydroxy - propane, and 1 - hydroxy - 2,3 - dichloropropane; methyl, ethyl and 2-chloro-ethyl ethers of these chlorhydrins; 2-chloroethyl mercaptan and 2-chloro-ethyl methyl sulphide; 2-chloro-furan (under pressure), 2-3-dichloro-1,4-dioxane, and 2-chlorothiophene. The ligno-cellulosic material may be cereal straws and particularly woods such as spruce, larch, pine, fir, poplar, beech and eucalyptus. In an example eucalyptus chips are refluxed with a mixture of ethylene chlorhydrin and glacial acetic acid the cellulose filtered off and further purified for use in artificial silk manufacture (see Group IV (a)). The filtrate is mixed with water to precipitate the lignin and treated to recover the solvents. The filtrate may be fortified with acetic acid and re-used for treating further wood before finally precipitating the lignin. In other examples wood chips are similarly treated with epichlorhydrin and acetic acid, epichlorhydrin and xylene and 2-chloro-ethyl acetate and acetic acid respectively. Specification 679,833, [Group IV (a)], is referred to.