Cellulose derivative compositions suitable for use in the manufacture of artificial leather and the like comprise a fatty substance having a normal iodine number below 135 and, as a rancidity inhibitor for the fatty substance, a phenol with two aromatic nuclei separated in the ortho or para position by oxygen or carbon, or a monohydric phenol having one aromatic nucleus and not more than two reactive positions, such as a monoalkyl ether of hydroquinone, an o- or p-alkyl phenol, or a dialkyl phenol. The fatty substance may be castor oil, olive, rapeseed, cod-liver, corn, peanut, cocoa-nut, cottonseed, palm, lard, or neatsfoot oil, or butter fat, lard, beef tallow, or wool fat. The fatty substance is of the semi-drying or non-drying type. It may comprise fatty glycerides or other fatty esters such as those of ethyl, butyl, ethoxy-ethyl, or benzyl alcohol, or of ethylene glycol, propylene glycol, diethylene glycol, or pentaerythritol. The cellulose derivative may be cellulose acetate, nitrate, or propionate, or ethyl, benzyl, lauryl, or crotyl cellulose. The rancidity inhibitor may be present to the extent of 0,25--5 per cent of the weight of the oil. Coatings of white or pale blue colour are obtained by the addition of lithopone and ultramarine. The rancidity inhibitor may be diphenylolpropane, diphenylolethane, dihydroxy-o-tolyl dimethyl methane, ortho or para hydroxy diphenyl ether, diphenylol propane formaldehyde condensation product, phenol-dipentene condensation product or a similar product obtained from cresol or guaiacol, mono methyl ether of hydroquinone, ortho or para cyclohexyl phenol, o-cresol, carvacrol, 1 : 2 : 4-xylenol, or an ethyl, propyl, butyl, amyl, lauryl, or cyclohexyl ether of hydroquinone, or an ethyl, propyl, butyl, or heptyl phenol. The inhibitor may contain chlorine in the aromatic nuclei or it may be a naphthol derivative. In an example, a composition for making artificial leather comprises cellulose nitrate, ethyl alcohol, ethyl acetate, a pigment, castor oil, and a small proportion of rancidity inhibitor. A measure of the resistance to rancidity is obtained by placing a piece of fabric coated with the composition in a stoppered flask maintained at constant temperature and exposed to the light from a carbon are. The odour developed is compared with that from a piece of fabric coated with a composition not containing the rancidity inhibitor. The compositions are also resistant to the discolouring effect of light and moisture. The Specification as open to inspection under Sect. 91 comprises the application of the process to the manufacture of films and other materials. This subject-matter does not appear in the Specification as accepted.ALSO:For preventing semi-drying or non-drying fatty substances from going rancid there is mixed therewith a phenol with two aromatic nuclei separated in ortho or para position by oxygen or carbon, or a monohydric phenol having one aromatic nucleus and not more than two reactive positions, such as a mono-alkyl ether of hydroquinone, an o- or p-alkyl phenol, or a dialkyl phenol. The fatty substance is one having an iodine number below 135, e.g. castor, olive, rapeseed, cod-liver, corn, peanut, coconut, cottonseed, palm, lard, or neatsfoot oil, or butter fat, lard, beef tallow, or wool fat. It may be a glyceride or other fatty ester such as one from ethyl, butyl, ethoxy-ethyl, or benzyl alcohol, or ethylene glycol, propylene glycol, diethylene glycol, or pentaerythritol. The rancidity inhibitor may be diphenylol ethane or propane, dihydroxy-o-tolyl dimethyl methane, o- or p-hydroxy diphenyl ether, diphenylol propane formaldehyde, phenol-dipentene or similar condensation product from cresol or guaiacol, hydroquinone mono methyl ether, o- or p-cyclohexyl phenol, o-cresol, carvacrol, 1.2.4. xylenol, or an ethyl, propyl, butyl, amyl, lauryl, or cyclohexyl ether of hydroquinone, or an ethyl, propyl, butyl, or heptyl phenol. It may contain chlorine in the aromatic nuclei or it may be a naphthol derivative. The resistance to rancidity is measured by comparing the odour developed on exposure to carbon-arc light of coatings containing the fatty substance and inhibitor, with the odour developed under similar exposure by coatings containing the fatty substance without the rancidity inhibitor.