320,842. Dreyfus, H. April 18, 1928. Cellulose carboxylates.-Cellulosic materials are acylated with chlor- or brom-aliphatic acid anhydrides to prepare halogen substituted cellulosic derivatives, which may be used to prepare cellulosic derivatives of amino- and substituted amino-aliphatic acids or of hydroxy aliphatic acids. Any chlor- or brom-substituted aliphatic acid anhydrides corresponding to acids containing only one atom of chlorine or bromine as for example chlor- or brom-acetic acid or a or #-chlor- or brom-propionic acid, or two or more such atoms may be employed. Mixed esters may be prepared by employing another anhydride, for example acetic anhydride or its homologues, in addition to the halogen aliphatic anhydride, for example by first treating with the halogenated anhydride and then with the fatty acid anhydride. As initial cellulosic materials, there may be employed cotton or other celluloses or near conversion products thereof, or bamboo, esparto, or wood pulps from which the lignin, pentosan, resin, and like constituents have been substantially removed, as for example in sulphite, soda, or sulphate, pulps. The cellulosic materials may be treated, prior to acylation, with organic acids particularly formic or acetic acids or mixtures thereof. Chemical pulps are preferably subjected to an alkaline purifying treatment as described in Specification 249,173 followed by the treatment with organic acids. The pretreatment with organic acids may be conducted in any convenient manner, for example with concentrated or dilute acids or with the vapours of the acids as described in Specification 268,938, the vapours being employed alone or mixed with air or other inert gas. Alternatively the cellulosic materials may be pretreated with hydrochloric or other hydrohalide acid or mixtures thereof as described in Specification 312,098, particularly when hydrochloric or other hydrohalide acid is employed in the subsequent acylation. The metallic halide catalysts referred to below for use in conjunction with hydrohalide acid in the acylation may moreover be used alone or together with the acid pretreating agents and the pretreatment with hydrohalide acids may be combined with a pretreatment with organic acids or alternatively the organic acids may be employed with other mineral acids, for example sulphuric acid. The acylation may be conducted in presence of suitable catalysts, for example sulphuric acid, benzene sulphonic acid, bisulphates e.g., sodium bisulphate, zinc chloride, phosphoric acid, or sulphuryl chloride. Metallic halides, particularly chlorides of iron, tin, manganese, copper, nickel, or cobalt may he employed in conjunction with hydrochloric or other hydrohalide acids, while ferric and stannic chlorides may be employed alone. The acylation processes may be carried out in presence of solvents for the cellulose, derivative produced or in presence of non-solvents or mixtures thereof or substantially in absence of liquid solvents or diluents by employing vapours of the anhydride. In examples, cotton linters are pretreated with formic acid of about 75-85 per cent strength and after hydroextracting or washing, centrifuging, and drying are acylated in a mixture of chloracetic acid, chloracetic anhydride, and sulphuric acid or in a mixture of chloroform, cbloracetic anhydride, and sulphuryl chloride. In another example, cotton fibre is pretreated as in the first examples and then acylated in a mixture of chloracetic acid, benzene, chloracetic anhydride, and sulphuric acid, so that the cotton fibre is converted into chloracetate without losing its fibrous form. The halogen substituted cellulose derivative may be converted into other derivatives by wholly or partly replacing the halogen by treatment with hydrolysing agents, for example dilute caustic soda solution, some of the derivatives thus obtained corresponding to the derivatives obtained by treating cellulosic materials with hydroxy aliphatic anhydrides as. described in Specification 316,160. The hydroxycontaining derivatives may be further esterified, for example with acetic anhydride to produce acidyloxyalkacyl derivatives or mixed alkacylacidyloxyalkacyl derivatives of cellulose. Further, the halogen substituted cellulose derivatives may be converted into other derivatives by treatment with ammonia or organic amines, for example methylamine, dimethylamine, ethylamine, diethylamine, aniline, or methyl- or ethyl-aniline, for instance in presence of an inert solvent or diluent or in gas or vapour form. The cellulose derivatives containing amino- or substituted amino groups have an affinity for acid dyestuffs. In examples, cellulose chloracetate is treated with alcoholic caustic soda and the cellulose glycollate produced is separated and washed; chloracetylated cotton fibres are treated with ammonia; cellulose chloracetate is treated with a solution of diethylamine or aniline in absolute alcohol and the product separated, washed with alcohol, and dried. The Provisional Specification refers also to the employment of zinc chloride in conjunction with hydrohalide acid, for example hydrochloric acid, or halides of phosphorous, antimony, or arsenic with or without hydrohalide acid as catalysts in the acylation processes.