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CHEMICAL NEWS, April 8, 1909

CA

THE CHEMICAL NEWS.

VOL XCIX., No. 2576.

THE THEORY OF DYEING.

By S. H HIGGINS, M Sc.

PERHAPS there is no part of chemistry concerning which so many speculations have been made, and so few really quantitative experiments carried out than that portion dealing with the actions taking place during dyeing operations. Many observations have been made and deductions drawn, but yet there is a surprising lack, in this branch of applied chemistry, of the large amount of accurate work which is so characteristic of practically all other branches of chemical science. The art of dyeing is very old, for Pliny observed polygenetic colour dyeing and the application of different mordants; nevertheless, we have not progressed very far towards a true explanation of the phenomena observed during the dyeing of textile fibres.

The different theories which have been advanced may be divided into (1) The Chemical Theory; (2) the Solution Theory; (3) the Mechanical Theory. It is true that other theories also exist of the nature of chemicomechanical, but the above are the definite classes of opinion. The chemist with pardonable pride attempts to explain the process by saying that chemical combination takes place during dyeing, and that the product is mainly the result of chemical action between the fibre and the dye-stuff. He is imbued with the all-embracing nature of his science, and resembles the apostle of electrolytic dissociation who is busy attributing all chemical actions to the whims of those mysteries-the ions.

It is evident from the literature which is issued from time to time that most investigators of the dyeing process support the chemical theory; but it is also noticeable that most of their conclusions are based upon investigations of animal fibres, as silk and wool, whereas the actions taking place during the dyeing of vegetable fibres, as cotton and linen, have been left almost entirely without elucidation. It is maintained that silk and wool are capable of entering into definite chemical reactions with dye-stuffs, but whereas it is realised that cellulose, which is the chief constituent of vegetable fibres, cannot exhibit strong acidic or basic properties, yet the vegetable kingdom is left alone, and broad generalisations are made from experiments on the other fibres mentioned. At the outset it must be recognised that any theory of dyeing must include all classes of dyeing operations.

The solution theory was advanced in 1890 by Witt, and was the attempted application of the solid solution theory of physical chemistry to explain the phenomena observed during dyeing operations. This theory displayed the genius of its author, and afforded plausible explanations of many experiments, but in other respects it was found lacking. Witt drew attention to the fact that wool dyed with magenta was of the same colour as a water solution of magenta, and not the dark green colour of the magenta crystals. He said that this observation supported his contention that the magenta was dissolved in the wool. It was shown by Von Georgevics, however, that if magenta crystals are only made fine enough they also exhibit the red colour of the solution in water. Further, Walker and Appleyard, working with picric acid, made observations which were incompatible with Witt's conclusions, and thus the new theory of dyeing was shaken at its foundations.

The formation of theories is usually left to the greatest minds, to those of a philosophical turn, and it is possible that in this selection long experience of practical dyeing has seldom entered into the formulations.

The mechanical theory is to the effect that the dye-stuff is drawn from solution and held in some peculiar physical

169 manner by the fibre. Walter Crum gave a splendid exposition of this view in the sixties, but since that time

chemical theory has been so much in evidence and chemical explanations so plausible that the process of dyeing has had to fall in and submit to the popular explanation. Nevertheless, on reading Crum's work one cannot help being struck with its merit, and one marvels that, in spite of this well-known work, the chemical theory of dyeing has gained so many adherents.

In support of the mechanical theory of dyeing some papers have recently been issued, e.g., Hübner, "Experimental Investigation of the Process of Dyeing" (Trans. Chem. Soc., 1907). It is well known that charcoal and other solids possess the property of extracting dye-stuffs from solution; in the case of charcoal the tinting effect is not noticeable, but if a white substance, as China clay, be used, then it is seen that the solid is dyed. It has been stated that in such cases the dye-stuff can be wholly washed out by water, but Hübner showed that these solids behaved either like wool or like cotton during the treatment with water to remove the dye-stuff. Thus it was found that charcoal behaved similarly to wool during every treatment to which wool is submitted in commercial dyeing, and likewise graphite was found to fall in with the usual methods of dyeing cotton; in both cases the fastness to washing was similar.

In pursuance of this line of research the present writer has recently issued (Higgins, Journ. Soc. Chem. Ind., 1909, xxviii., 188) an account of experiments which further support the mechanical theory of dyeing. Wool was beaten in a beating engine to five different states of division, and the samples obtained were dried. They were then allowed to absorb dye-stuff from solution and moisture from the air. It was found that the maximum absorption of dye-stuff and of moisture took place during, approximately, the same time, and that this maximum amount in both cases was practically constant for all states of division. Samples of cotton mercerised, bleached, and unbleached, were found to absorb iodine from weak potas. sium iodide solution in proportion as they absorbed moisture from the air. A striking result was obtained by plotting the moisture contents of cotton-yarn mercerised with dif ferent strengths of caustic soda solution. The moisture curve was found to closely resemble the dye trial curve obtained when a substantive cotton dye-stuff was used; in short, the mercerised cotton samples only absorbed more dye-stuff in so far as they absorbed more moisture. The experiments bring out a marked similarity between the absorption by textile fibres of a solid from a liquid medium, and of a vapour from a gaseous medium, and as the absorption of moisture from air is relegated to that class of little understood phenomena known as surface attraction, it must therefore be taken that the dyeing of textile fibres also belongs to that class of physical action.

THE FRUIT OF VIBURNUM NUDUM.

By ROBERT H. LOTT.

THE fruit of Viburnum nudum was gathered in the swampy portions of the territory around Sylvan Beach, New York, August 27 to September 5, 1907. It grows on shrubs four to seven feet in height. The species is common in swampy regions from the New England States to Florida. The portion gathered August 27 was comparatively green, while on the 4th and 5th of September it had become quite ripe. It was then a beautiful cardinal red, very abundant in the neighbourhood of Sylvan Beach, and the most gorgeous object in the early autumn landscape.

The dried fruit of this viburnum consists of berries that resemble commercial currants. They differ in that their colour is bluish black instead of brownish black, and they are more elongated. The odour of the berries is also similar to that of currants.

to be cholesterol.

After separating the ethereal layer the remaining liquid was acidified with sulphuric acid and slightly heated, whereupon the fatty acids liberated by saponification collected upon the top of the liquid. These were separated and boiled with distilled water for several hours. They were afterwards separated from the water, dried on the water-bath, and found to weigh 3.6033 grms., more than the amount of oil at first taken. The increase in weight is due, doubtless, to the oxidation of the acids. Two distinct acids appeared, one very clear and odourless which crystallised in a freezing mixture to fine needles and melted at about 4°; the other was a yellow limpid liquid, with an odour resembling lard. This last crystallised at a low temperature, but we did not succeed in finding the meltingpoint. Judging from the descriptions given in the literature the clear acid seems to be oleic, and the yellow one linoleic. Both reacted acid to litmus-paper.

An attempt was made to obtain the weight of the soluble fatty acids. The acidified liquid first separated from the insoluble fatty acids, and the distillate exactly neutralised by normal caustic soda, using phenolphthalein as an indicator. The washings from the insoluble acids were now added to the contents of the flask and again distilled to a small bulk. This distillate also was neutralised with normal caustic soda. The two distillates were evaporated to dryness to constant weight. The number of centimetres used in the neutralisation was multiplied by 0.022 and the product subtracted from the constant weight. The result was unsatisfactory. Each fruit bears a single flat stone which undoubtedly contains the oils.

The Proteins.

Some of the berries were crushed and boiled in distilled water for a short time. A small amount of this solution was heated with nitric acid, giving a yellow colour, which became an orange-red when made alkaline. This showed the presence of albumen.

A portion of the fruit was heated with an excess of soda-lime in a dry test-tube. The fumes reacted alkaline to litmus-paper. A similar effect was produced by heating the berries alone at a high temperature.

The nitrogen was determined by the Kjeldahl method. 2'0933 grms. of the berries gave o‘0112 grm. of nitrogen, equivalent to 0.53 per cent.

A quantity of solution which resulted from boiling the berries in distilled water was tested to learn if the albumen contains sulphur. We treated a solution of lead acetate with caustic soda until the precipitate which first forms is re-dissolved. The fruit solution was now added to this and heated to boiling. A dark coloured precipitate of lead sulphide formed, which indicated the presence of sulphur,

RECENT RESEARCHES IN RADIO - ACTIVITY.* By Prof. ERNEST RUTHERFORD, M.A., LL.D., D.Sc., F.R.S.

IN 1904 I had the honour of giving an Address at the Royal Institution on the subject of radio-activity. In the interval steady and rapid progress has been made in unravelling the In the present tangled skein of radio-active phenomena. lecture I shall endeavour to review very shortly some of the more important advances made in the last few years, but as I cannot hope to mention, even briefly, the whole additions to our knowledge in the various branches of the salient facts in the development of which I have taken subject, I shall confine my attention to a few of the more

some small share.

active phenomena on the disintegration theory put forward In my previous lecture I based the explanation of radioin 1903 by Rutherford and Soddy, which supposes that the atoms of the radio-active bodies are unstable systems which break up with explosive violence. This theory has stood the test of time, and has been invaluable in guiding the experimenter through the maze of radio-active complications. In its simplest form, the theory supposes that every second a certain fraction (usually very small) of the atoms present become unstable and explode with great violence, expelling in many cases a small portion of the disrupted atom at a high speed. The residue of the atom forms a new atomic system of less atomic weight, and possessing physical and chemical properties which markedly distinguish it from the parent atom. The atoms composing the new substance formed by the disintegration of the parent matter are also unstable, and break up in turn. The process of degradation of the atom, once started, proceeds through a the successive disintegrations of the parent matter are in most number of distinct stages. These new products formed by cases present in such extremely minute quantity that they cannot be investigated by ordinary chemical methods. The radiations from these substances, however, afford a very delicate method of qualitative and quantitative analysis, so that we can obtain some idea of the physical and chemical properties of substances existing in an amount which is far below the limit of detection of the balance or spectroscope.

The law that governs the breaking up of atoms is very simple and universal in its application. For any simple substance the average number of atoms breaking up per second is proportional at any time to the number present. In consequence, the amount of radio-active matter decreases in a geometrical progression with the time. The "period of any radio-active product, i.e., the time for half the matter to be transformed, is a definite and characteristic property of the product which is uninfluenced by any of the laboratory agents at our command. In fact, the period of any radio-active product, for example, the radium emanation, if determined with sufficient accuracy, might well be taken as a definite standard of time, independent of all terrestrial influences.

The law of radio-active transformation can be very simply and aptly illustrated by an hydraulic analogy. Suppose we take a vertical cylinder filled with water, with an opening near the base through which the water escapes through a high resistance. (A short glass tube in which is placed a plug of glass-wool is very suitable). When the discharge is started, the amount of water escaping per