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plished during the past four years rested most heavily and how well they have borne i t is not generally known and therefore should be given special mention. The dean of these men is Dr. R. C. R. Taggesell, chief chemist. of the National Aniline & Chemical Company, Inc., whom the writer has worked with and known intimately for a long period of years. I can state frankly that i t is my opinion that without his superior knowledge and untiring efforts the industrywouldnot stand where it does to-day. I am glad the opportunity has presented itself to publicly proclaim this fact, knowing full well that the modesty of the man would prevent it from becoming known in any other way.
APPLICATION OF DYESTUFFS IN COTTON DYEING By J. MERRITTMATTHEWS Consulting Chemist, New York City
Cotton has become one of the principal textile fibers of the world and now ranks alongside of wool and silk as the three great sources of clothing material to meet the needs of the human race. A great many will probably consider that cotton has always been in a very important position in this respect, but this is not the case. It has been only during the last century that cotton has come to the front, and this has been brought about by the mechanical improvements in ginning, spinning, and weaving, and t o a great extent also by the manufacture of dyestuffs capable of readily dyeing the cotton fiber. Before the introduction of the coal-tar dyestuffs, the dyeing of cotton, like the dyeing of wool or silk or linen, was dependent on the use of the natural dyes and certain mineral pigments. As most of the natural dyes require to be combined with a metallic mordant before they yield useful and serviceable colors, and as the cotton fiber has very little power of combination, or so-called affinity, for metallic salts, the dyeing of cotton was attended with many difficulties which were not present in the case of wool, as this latter fiber readily combines with many metallic salts that serve as useful mordants. In order t o prepare the cotton with a satisfactory mordant of metallic salt i t was frequently necessary to carry out very devious and complicated operations, the very complexity of which caused the results to be uncertain and exceedingly difficult to maintain uniform. This is readily manifest on referring to some of the old recipes employed for the dyeing of cotton with the vegetable dyes. With the advent of the coal-tar dyes i t was soon discovered that many of them could be applied t o cotton by relatively simple and effective methods. The basic colors which were first introduced, it is true, still required a mordant in their application t o cotton, in this case the mordant consisting of tannic acid fixed in the fiber by the use of a metallic salt, such as tartar emetic. However, even this method of dyeing was a great advance in simplicity and a person of average intelligenceand resourcefulness could soon master the art of dyeing by this means. The acid colors which soon came into the market, i t is true, were only adapted t o wool and silk, and found little application to cotton, but when the benzidine or direct cotton colors were introduced a new field in cotton dyeing was opened up and the widespread use of dyed materials was much stimulated. These colors, however, though varied and pleasing, were limited in fastness, and this naturally restricted the utilization of cotton fabrics. The introduction of aniline black as a specialized feature in cotton dyeing, however, greatly helped to extend the use of dyed cotton materials by providing an extremely fast color. The later introduction of various sulfur dyes also stimulated the use of cotton material by providihg a number of fast shades. With the advent of the so-called vat dyes, however, permitting of the production on cotton of a wide range of beautiful shades of the highest possible qualities of fastness, cotton fabrics were lifted out of their previous rather low-grade class and elevated
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t o the rank of fabric aristocracy. At the present time, therefore, it may be said that cotton materials are used for highgrade fabrics, and in consequence demand the application of high-grade colors. I n the application of dyestuffs to cotton we must consider several factors of prime importance. In the first place, the form in which the cotton is dyed will have much influence in the selection of the dyestuff. Cotton may be dyed in the form of raw stock or loose unspun fiber,as cotton sliver; or in a partially manufactured condition, as yarn (either as skeins or hanks), as warps, or as yarns on cops or tubes. Or the cotton may be dyed in the fabric form, either as a woven piece or as a knitted fabric. Dyestuffs that are suitable for raw-stock dyeing may not be suitable for dyeing woven cloth or knit fabrics, and vice versa. Cotton warp dyeing requires special consideration as t o dyestuffs. Cops and tubes are dyed in special machines and the method of dyeing imposes certain restrictions on the kind of dyestuffs to be used. It will be seen, therefore, that the man who contemplates manufacturing and marketing cotton dyestuffs must be more or less familiar with the processes of cotton manufacture to be in a position t o properly select the products that are the more desirable. Another consideration that is important in selecting cotton dyes is the kind of material into which the fabric will be manufactured and the eventual use t o which it will be put. This will determine the qualities of fastness of the dyestuff t o be employed. Cotton goods go into all kinds of materials at the present time; we have shirtings for men, blouse and skirt material €or women. These are more or less in fancy colors, but as a rule the amount of color is only a small proportion of t h e total fabric. These goods are subject to repeated washing and laundering, and they must also stand exposure to light and perspiration, so it can readily be seen that the colors must be fast to these agencies and a high class of dyestuff is required. Before the war the vat dyes were being largely used for these goods and the public was being educated t o expect a color t h a t would last even longer than the fabric under the severe conditions of laundering, especially as most modern laundries now employ strong bleaching agents, such as hypochlorite of soda, for the rapid whitening or bleaching of the cotton goods. Under the present conditions there are practically none of these v a t dyes available, as they are not being manufactured in this country and it is t o be presumed that all the old stocks on hand have been used up. We also have ginghams and fancy cotton goods which have become quite popular as dress fabrics during the past couple of years, replacing light weight woolens and worsteds, and even silk to a considerable degree. The dyeing in this case isalscs chiefly in fancy colors and should possess about the same degree of fastness as just related, for these are all wash fabrics. Next we have cotton denims used so extensively for overalls and similar garments. Though this class of fabrics is perhaps not so much before the eye of the general public as some others, it is one of the great staples of the cotton business and very large amounts of dyestuffs are used in them. The principal color used is blue, the fancy shades being negligible in amount, and the chief dyestuff used is indigo-in fact, this is where t h e great bulk of indigo is used. The color has t o withstand very severe usage and repeated washings. Logwood can be used t o approximate the shade, but the fastness is very inferior. Sulfur blues can be used with good advantage, and there are some who may be inclined to maintain that sulfur blue is as. satisfactory for this work as indigo. Hydron blue, which may also be classed as a sulfur dye, though in reality i t is a vat dye, is eminently satisfactory, in fact, in many respects it may be considered as superior to indigo. But the trade has long been accustomed to indigo and i t will probably stick to it for a long, time to come.
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goods are dyed with mineral or pigment colors to produce the khaki brown. This color is obtained with a mixture of chrome and iron salts by simple precipitation of the oxides in the fiber. Sometimes manganese salts are also used, but a t the present time these are scarce and of high cost. In respect to tonnage of cotton dyed, this mineral khaki brown forms a very important item, as the cloth dyed in this way is mostly heavy canvas for tent material, wagon covers, tarpaulins, etc. In the selection of dyestuffs for cotton from the dyestuff manufacturer’s point of view, the first consideration is the quantity of the dye consumed by the trade. If this is only small and represents but an insignificant turnover during the year, it does not appeal to the business sense as an attractive proposition. Before the war the various German dyestuff houses had on the market quite a large number of direct cotton colors-one would believe almost too many for profitable production. Many of these varied very little in shade and properties, and the consumption of many was relatively small. It is hardly to be presumed that our American manufacturers are going to bring out all these various brands of dyestuffs. The most sensible procedure would be to fix on those which offered the most advantages with respect to quality of color and fastness, and if there are several very near duplicates of one another, select for manufacture the one most economical to produce. We must also bear in mind that many of the direct cotton colors have a serious lack of fastness to washing, and while they are extremely simple and easy to apply and give good clear colors in combination, yet fastness to washing is being more and more required for colored cotton goods, and dyes which do not possess this fastness will have a very limited use. It is believed that in the dyeing of cotton the sulfur dyes will have a greater development in this country than they ever had before. It is true they are somewhat limited in range of shades, but blacks, blues, browns, yellows, green, and orange are within the list. They also have the limitation that they are rather dull in tone. But their good fastness t o washing is greatly in their favor; also their fastness to acids allow of their use in cross-dye work which much extends their field of application. A large number of useful shades can be obtained by combinations of the sulfur dyes, although the want of a satisfactory red and green dye in this class seriously limits the possibilities for the production of,fancy shades,
NATURAL DYESTUFFS-AN IMPORTANT FACTOR IN THE DYESTUFF SITUATION By EDWARD S. CHAPIN Consulting Chemist, Boston, Massachusetts
