Mercerizing

Mercerizing Piece Goods.

For pieces stentering machines are used. In these two endless chains carry clips which run in slotted grooves in the horizontal frame of the machine which is about 4oft. in length. The clips nip the cloth automatically on either side as it is fed into the machine from an impregnating bath and tension rollers (warp), at the same time the two rows of clips diverge and when the cloth has travelled about one-third of the length of the machine it is stretched slightly beyond its original width. At this point the cloth meets a spray of water from spurt pipes. The tension slacks and the mercerizing is effected. When the piece arrives at the end of the machine the clips open and release it. It is most economical and satisfactory to mercerize before bleaching, but the recovery and concentration of the caustic soda (usually carried out in multiple effect evapo rating plant) is not attained without difficulty for it is always con taminated with impurities, the constituents of the cotton which has been treated. The action of caustic soda on bleached cotton is complete in 3o seconds, but in the case of unbleached cotton an appreciable time is taken in wetting out the material. In order to save this time, or boiling out to some extent before mercer izing or the risk of uneven treatment, some people make use of certain agents for the purpose of effecting rapid wetting. The product Prestabit is stated by Rath (1928) to be very efficient in this respect. Cotton mercerized under tension has a greater affinity for colouring matters than ordinary cotton but not quite so much as that mer cerized without tension. Mercerized cotton which is dried before dyeing takes up less colour than that dyed in a moist or air dried condition. Air dry untreated cotton contains 7.8% moisture, air dry mercerized cotton 12.6%.

The action of caustic soda on cotton was regarded by Mercer as a chemical reaction in which one molecule of cellu lose combined with one of caustic soda; by washing with water the radicle is replaced by In 1852 J. H. Gladstone found that the composition corresponded to 2Co11,005.Na0H. This is in agree ment with the moisture content of the washed and air dried mer cerized cotton. Since 190o many workers have attempted to deter mine the composition of alkali cellulose and some have cast doubt on the chemical nature of the action but it is evident that beyond a certain .concentration (about 32°Tw) there are distinct signs of chemical action and the amount of caustic soda (of usual mercerizing strength) taken up by cotton agrees closely with Gladstone's formula. Knecht and Platt (1925) conducted a series of nine experiments using solutions of caustic soda from 20°—Ioo°Tw. The amount of caustic soda taken up was 12.3% at 4o°Tw and above that strength it was practically constant. Ermen and Jenkins (1927), using a similar method with certain modifica tions, found 25.7% caustic soda absorbed between 35° and 5o°Tw caustic soda, but after that an increasing amount of caustic ab sorbed (25%) with 82°Tw. It is very difficult quantitatively to manipulate small experiments with caustic soda above 7o°Tw. The space lattice of mercerized ramie cellulose as developed from X-ray data has been the subject of investigations by 0. L. Sponsler and W. H. Dore (July 1928), who find definite evidence of action above a critical concentration of 13% caustic soda. With hot caustic soda a greater concentration is required and ice cold caustic may be of a lower concentration for mercerizing.

The colouring matter benzopurpurine may be utilized in test ing for mercerization, by dyeing the cotton a full shade of red and then destroying the colour with titanous chloride in dilute hydrochloric acid solution. Just before the colour entirely dis

appears mercerized cotton shows a pink colour, untreated cotton remains blue until the colour vanishes. The ratio of the amount of benzopurpurine 4B taken up by untreated and mercerized cot ton supplies a means of estimating the extent of mercerization. A test with a solution of iodine in potassium iodide together with a zinc chloride solution depends upon the indication of a blue colour in the case of mercerized cotton. Treatment with a mixture containing 32o cu.cm. sulphuric acid, 12o°Tw and 26o cu.cm. for maldehyde 40% for 2min. and washing increases the affinity of mercerized cotton for chlorazol sky blue to such a great extent that it is still more easily distinguished from ordinary cotton treated with the reagent.

Many other reagents besides caustic soda modify the properties of cotton in a similar manner. Some of these were known to Mer cer, sulphuric acid of I05°Tw and zinc chloride 145°Tw being included in the first patents. Nitric acid of 83°Tw acts very simi larly to caustic soda and Knecht has shown that a compound with one molecule of nitric acid per molecule of cellulose is formed. It is decomposed by washing with water. Marshall finds that the lustre of China grass is improved by treating with nitric acid 83°Tw without tension. The lustre of linen is improved by mer cerizing. Viktorov (1925) showed that in mercerizing linen there was a fall in strength which might amount to io% but with 53°Tw caustic soda a 40% increase in dyeing affinity for direct colour was observed. (E. Hi.) MERCHANDISE MARKS. The first attempt to make the falsification of trade marks a criminal offence was in the British Merchandise Marks act 1862. After the international conven tion for the protection of industrial property, made at Paris in 1883, to which Great Britain acceded in 1884, the Merchandise Marks act 1887 was passed generally to make better provision for the protection of merchandise. It was amended in 1891, and 1911. By these statutes, a person is guilty of an offence, punishable on indictment or summary conviction by fine or im prisonment, who does any of the five following acts, unless he proves as regards the first four of them that he acted without intent to defraud (there is a special defence to No. v. which is noted below) : (i.) forges any trade mark, or makes, disposes of, or has in his possession for such purpose any die or instrument; (ii.) falsely applies any trade mark or a colourable imitation of any trade mark to goods; (iii.) applies any false trade descrip tion to goods ; (iv.) causes any of the above i offences to be com mitted; (v.) sells or exposes for sale, or has in his possession for sale, trade or manufacture, any goods or things to which any forged trade mark or false trade description is applied, or any trade mark or colourable imitation of a trade mark is falsely ap plied, unless the defendant proves that, having taken all reason able precautions, he had no ground to suspect the genuineness of the mark, etc., and also that on demand he gave to the prosecutor all the information in his power as to the person from whom he obtained the goods, or proves that he acted "innocently." "Trade description" is defined as any descriptive statement or other indication as to the number, quantity (not quality, it should be observed), or weight, place or mode of production, or the ma terial of the goods, or as to their being subject to an existing pat ent, privilege or copyright. The test of what is a trade description depends upon the understanding of the trade and not on scientific correctness (Fowler v. Cripps, 1906, I K.B. 16).