The more important general indications of the above results are—(1) The mercerisation action commences with a lye of 10°B., and increases with increased strength of the lye up to a maximum at 35°B. There is, however, a relatively slight increase of action with the increase of caustic soda from 30-40°B. (2) For optimum action the temperature should not exceed 15-20°C. (3) The duration of action is of proportionately less influence as the concentration of the lye increases. As the maximum effect is attained the action becomes practically instantaneous, the only condition affecting it being that of penetration—i.e. actual contact of cellulose and alkali.

(d) The question as to whether the process of 'mercerisation' involves chemical as well as physical effects is briefly discussed. The author is of opinion that, as the degree of lustre obtained varies with the different varieties of cotton, the differentiation is occasioned by differences in chemical constitution of these various cottons. The influence of the chemical factors is also emphasised by the increased dyeing capacity of the mercerised goods, which effect, moreover, is independent of those conditions of strain or tension under mercerisation which determine lustre. It is found in effect that with a varied range of dye stuffs a given shade is produced with from 10 to 30 p.ct. less colouring matter than is required for the ordinary, i.e. unmercerised, goods.

In reference to the constants of strength and elasticity, Buntrock gives the following results of observations upon a 405 twofold yarn, five threads of 50 cm. length being taken for each test(Prometheus, 1897, p. 690): (a) the original yarn broke under a load of 1440 grms.; (b) after mercerisation without tension the load required was 2420 grms.; (c) after mercerisation under strain, 1950 grms. Mercerisation, therefore, increases the strength of the yarn from 30 to 66 p.ct., the increase being lessened proportionately to the strain accompanying mercerisation. Elasticity, as measured by the extension under the breaking load, remains about the same in yarns mercerised under strain, but when allowed to shrink under mercerisation there is an increase of 30-40 p.ct. over the original.

The change of form sustained by the individual fibres has been studied by H. Lange [Farberzeitung, 1898, 197-198], whose microphotographs of the cotton fibres, both in length and cross-section, are reproduced. In general terms, the change is from the flattened riband of the original fibre to a cylindrical tube with much diminished and rounded central canal. The effect of strain under mercerisation is chiefly seen in the contour of the surface, which is smooth, and the obliteration at intervals of the canal. Hence the increased transparency and more complete reflection of the light from the surface, and the consequent approximation to the optical properties of the silk fibre.

The work concludes with a section devoted to a description of the various practical systems of mercerisation of yarns in general practice in Germany, and an account of the methods adopted in dyeing the mercerised yarns.

RESEARCHES ON MERCERISED COTTON.

A. Fraenkel and P. Friedlaender (Mitt. k.-k. Techn. Gew. Mus., Wien, 1898, 326).

The authors, after investigation, are inclined to attribute the lustre of mercerised cotton to the absence of the cuticle, which is destroyed and removed in the process, partly by the chemical action of the alkali, and partly by the stretching at one or other stage of the process. The authors have investigated the action of alcoholic solutions of soda also. The lustre effects are not obtained unless the action of water is associated.

In conclusion, the authors give the following particulars of breaking strains and elasticity:—

Treatment Experiments Breaking strain
Grammes		 Elasticity Elongation in mm.
Cotton unmercerised. 1 360 20
2 356 20
3 360 22
Mercerised with Soda 35°B. 1 530 44
2 570 40
3 559 35
Alcoholic soda 10 p.ct. cold 1 645 24
2 600 27
3 610 33
Alcoholic soda 10 p.ct. hot 5 740 33
2 730 38
3 690 30