236 THE JOURNAL O F THE SOCIETY O F DYERS AND COLOURISTS. Sept., 1005.

(8 ) If several competitors have at the eame time solved the same problem satisfactorily, the prize may be divided amongst them in equal or unequal parts, according to the respective value of the work sub- mitted, at the sole discretion of the Adjudicating Committee.

Every competitor has the right to take out a patent for his process or invention, but the Society reserves to itself the right of puhlication. either wholly or in part, of the work submitted. According to the law in force in most countries, no diecovery is patentable which has boon made public previous to the date of the patent application. Consequently competitors who desire to patent their inventions should do so before submitting them to the Society, the latter declining all responsibility on this subject. In cases where an inventor has been awarded a prize hy the Society before i t is patented, he may reqiiest that the publication of his paper Ge adjourned for any period not exceeding six months.

The Society s i l l endeavour, as f a r as possible, t o return unsuccessful papers to the competitors, but they accept no responsibility under this head.

The Hon. Secretary of the Society will be glad to communicate with anyone desiring to include further problems in the above list.

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FORTHCOMING PAPERS.

WEST RIDING SECTION. October.-" Production of a Permanent Finish on Cotton

LONDON SECTION. October.-" The Dyeing of Wool 'hats," by Mr. J. W. LAMB. November.-"Notes on Garment Dyeing," by Mr. F. E.

Cloth," by Prof. E. KNECHT, Ph.D., &c.

ROBERTSON, F.C.S. _-

COMMUNICATIONS.

The Identification of Dyestuffs on Animal Fibres.

By ARTHUR G. GREEN, M.Sc., F.I.C., F.C.S., assisted by

H. YEOMAN and J. R. JONES (Department of Tinctorial Chemistry,

The University, Leeds). INTRODUCTORY.

The ready identification, by an examination of a textile material, of the dyestuff or dyestuffs with which it has been dyed or printed, is a problem which presents a t the present day great difficulties. Twenty or thirty years ago the number of dyestuffs was so small that their identification by an expert was a simple enough matter, for the shade alone would usually give a Sufficient indication. With the enormous increase both in individual colouring matters and in new groups of colouring matters their detection has been rendered both more necessary and greatly more difficult, since it is now possible to produce any shade in a large variety of ways. The fact that the fastness of such a shade for the purpose in view will depend upon a suitable choice of the dyestuff or dyestuffs, renders it particularly important for the dyer in matching II sample submitted, to b%able not only to match

Ihe shade, but, if necessary, to select the same or 3imilar dyestuffs. It is also a desideratum for the merchant to be able to ascertain whether the colour of the material dyed for him is always of constant composition, whether the shade dyed by one firm is or is not a chemical match €or that dyed by another, and other similar problems. Although an extensive series 0f tables has been published by Lange, Knecht and Lowenthal, Rawson, Lunge, Gnehm, Heermann, and others, giving the reactions of the individual dyestuffs on the fibre towards acids, alkalies, and stannous chloride, there yet exists a want for a systematic scheme of analysis, without which such tables are of little use. A scheme of this kind should be capable of referring the dyestuff to its chemical group, aIter which the particular brand may, if necessary, be ascer- tained by comparing the individual reactions with the published tables. In very many cases, however, sufficient information for the practical dyer would be gained by knowing the group to which the dyestuff belongs, the precise identi- fication of the particular individual not being always necessary.

Although for the present moment we shall leave out of consideration the identification of mixtures, which is often a most difficult and intricate problem, and shall limit ourselves to the consideration of single dyestuffs or mixtures of dyestuffs of the same class, yet it appears to be an absolute essential for any scheme of analysis that it should also be capable of extension to all the mixtures which may be encountered in practice. For this reason only such chemical properties can be employed as group reactions as depend not upon individual peculiarities, but upon general differences in chemical structure, so that dyestuffs of the same family shall be grouped together irrespective of shade. Another reason why only such a principle can prove satisfactory is that the scheme must be capable of referring to their respective chemical and dyeing groups the many new colouring matters which are constantly appearing and whose in- dividual reactions are still unknown.

Dyestuffs may be classified in two ways, either according to their dyeing properties, viz., whether basic, acid, salt,* mordant, vat, &c., or according to their chemical structure, that is, according to the chromophor they contain, viz., whether they belong to the nitro, nitroso, azo, triphenylmethane, azine, oxazine, thiazine, acridine, pyrone, anthracene, or other groups. In the scheme of analysis which we have to submit, we have made use in the first place of methods for ascertaining the dyeing property of the dyestuff on the fibre, such tests (so-called " stripping tests ") being an inversion of the respective dyeing process. In the second place, in order to ascertain the chemical relationship of the dyestuff, we have employed a modification of the method suggested

The 1.erm " salt " dyestuq: proposed by ,yeor$iwim, is employed in preference to the terms substantive or direct," both of which are open to objection.