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Attempts have been made to correlate the use of organic solvents as alternatives to water in textile processing with the ‘solubility parameter’ concept. Chlorinated hydrocarbons prove suitable for scouring and some finishing operations since their solubility parameters are ideal for such operations. In dyeing, however, the solubility parameter of polyester fibres, dyes and perchloroethylene are very similar, resulting in poor exhaustion of conventional disperse dyes. New solvent dyeing systems and new dyes, with high partition coefficients in polyester fibres, must be developed for solvent dyeing to become of practical consideration. Other solvents have been examined for solvent assisted dyeing. It has been shown that when benzyl alcohol and 2-phenoxy ethanol are used in dyebaths at concentrations at which these solvents are not completely in solution, both the rate of dyeing and penetration of dye into the fibre can be markedly increased in comparison to normal aqueous dyeing with polyester, nylon and acrylic fibres.

The reaction of flax yarn with acrylonitrile, chloroacetic acid, and β–propiolactone in presence of sodium hydroxide as catalyst has been studied. The results are compared with those obtained with cotton in earlier work. Under the experimental conditions used, measurable differences in reactivity between the two fibres are apparent. The cause of this difference in reactivity has been investigated and is explained by consideration of the effect of different concentrations of sodium hydroxide solutions on the two fibres. In general, for a given alkali concentration flax absorbs more sodium hydroxide and water than does cotton. This gives a greater change in the fine structure of the flax fibre produced by mercerising strengths of alkali. The effect of mercerising–strength sodium hydroxide on the nodes present in flax fibre, which act as major points of entry to the fibre, is also pointed out.

The decomposition of sodium chlorite during the bleaching of flax has been studied at different pH values and various temperatures. Bleaching with sodium chlorite should be accompanied by maximum formation of sodium chloride and minimum formation of sodium chlorate and chlorine dioxide. The oxidising power of the bleaching agent is discussed. Whilst there is a good margin of safety with sodium chlorite under normal bleaching conditions, extreme conditions must be avoided, in order to prevent chemical damage. The effect of sodium chlorite on the impurities present in cotton and flax is discussed. The use of hot, weakly acid oxidising solutions permits shortened bleaching processes. The main problems in practical sodium chlorite bleaching are (1) choice of a suitable method of activation of the bleaching agent, (2) selection of corrosion-resistant materials for construction of bleaching plant, and (3) design of the equipment to be used.

Presented at a Symposium on ‘Processing Textiles on Perforated Beams in the Dyehouse’ held by the Manchester Region at the Manchester College of Science and Technology, on 26 th March 1965, Mr M. R. Fox in the chair. Also presented at meetings of the Midlands Region, held in the King's Head Hotel, Loughborough, on 18th November 1964, Mr G. Whitehead in the chair; of the West Riding Region, held in the Victoria Hotel, Bradford, on 26th November 1964, Dr F. F. Elsworth in the chair; of the London Region, held at the Royal Society, Burlington House, London Wl, on 4th December 1964, Mr C. Barnett in the chair; of the Scottish Region, held in the St Enoch Hotel, Glasgow, on 15th December 1964, Mr B. W. Mills in the chair; and of the Bradford Junior Section, held at the Bradford Institute of Technology, on 18th January 1965, Mr V. L. Elsworth in the chair Laboratory methods are described for simulating high–temperature and atmospheric beam–dyeing conditions by means of the high–temperature dyeometer and a modified package–dyeing machine. Details are given of the rate–of–dyeing and migration behaviour of disperse dyes on polyester, cellulose triacetate, acrylic and polyamide fibres, of basic dyes on acrylic fibres, and of acid dyes on poly–amide fibres. Particular attention is drawn to the necessity for accurate temperature control during dyeing. A thorough knowledge of rate–of–dyeing and migration behaviour can be used to select dyes for three–colour mixtures and to determine their optimum application conditions.

The fundamental principles of radio-frequency heating are discussed. Microwave frequencies have been selected for a special study because of the availability of efficient magnetron valves for industrial use. The applications of this source of heat for the continuous fixation of dyes on textile fibres have been investigated.