600 



SCIENCE 



[N. S. Vol. XXXII. No. 826 



tests, based on chemical composition, for 

 genera and divisions and subdivisions and sec- 

 tions, for careful study with the spectroscope 

 in a dark room, to determine vrhether a dye- 

 stufE is a triphenyl methane or a nitro deriva- 

 tive. The sample is taken up, the class de- 

 termined and noted. It is found, for instance, 

 to be a salt color, on cotton, unmixed, a rather 

 dark shade of red. Out come the well- 

 thumbed sample books, Cassella, Metz, 

 Badische, Elberfeld, perhaps one or two 

 others, who have a good line of those colors. 

 The page of red salt colors on cotton is 

 reached, the sample is compared. In a minute 

 or two more it is cheeked off — probably Dia- 

 mine Fast Red B, Cassella — or Dianil Eed 

 BB, Metz ; then these are looked up in Schultz 

 & Julius, last edition, one or two simple tests 

 are made — probably a dab. or two of acid on 

 each — and the color is identified. 



In many cases the experience of the labora- 

 tory will fix on the color, and the sample 

 books, like the chemical tests, will only be 

 needed as confirmation. The sample, for in- 

 stance, is red worsted yarn, used in stockings. 

 The tests show an unmixed acid color, not 

 after chromed. It must, to be satisfactory, be 

 fast to washing and to perspiration. Only 

 one or two colors of this class answer these re- 

 quirements. The chemist knows, then, at 

 once, that it must be this, or that, or the 

 other. A few simple tests, and the particular 

 one is determined. 



A specially unfortunate result of the purely 

 theoretical character of the tests in this book is 

 the extraordinary way in which colors of en- 

 tirely different classes and shades, come out to- 

 gether in the final separations. The sections, 

 into which the compounds are finally classified, 

 after being broken up into genera, divisions 

 and subdivisions, are based on the shades 

 given on wool. Every dyeing chemist, when 

 he first sees that, will recognize it as a natural 

 and useful method of final classification. 

 Imagine his astonishment, then, when he in- 

 spects the colors forming one of these sec- 

 tions, as, for instance, one taken at random 

 on page 64, headed " Section of Yellow Orange 

 Colors on Wool," and finds among the eight 



colors there set down, Indian yellow J (an 

 acid yellow used on wool and silk), six salt 

 colors, dyeing cotton various shades of orange, 

 and a leather hlach! In almost every section 

 can be found acid and basic, salt and vat col- 

 ors mixed together in almost inextricable 

 confusion, and, thanks to the strange way in 

 which the dyeing tests on wool are made, in- 

 stead of the red colors being by themselves, 

 and the blues and violets and oranges all sep- 

 arated, as they would have to be for any use- 

 ful purpose, every color of the spectrum may 

 be brought together in the same class. 



A Color Standard. — There is, however, one 

 feature of Professor Mulliken's book which, 

 so far as we know, is new, and which might be 

 made extremely useful. In a pocket in the 

 back cover of the book are placed three card- 

 board sheets, containing a very carefully con- 

 structed color standard of nearly 150 different 

 shades, most conveniently arranged for com- 

 parison and identification. This color stand- 

 ard is constantly referred to, in the book, and 

 wherever possible every single one of all the 

 manythousands of tests set down in the tables 

 has the color reaction carefully and accurately 

 classified to correspond to its place in the 

 standard. 



This suggests an idea which might be de- 

 veloped into a treatise on modern dyestuffs, 

 which would be of real interest and value to 

 dyeing chemists all over the world. The diffi- 

 culty with " Schultz & Julius," and with 

 " Knecht, Eawson and Loewenthal," is that 

 they do not give sample dyeings of the colors 

 they describe, and so must be supplemented, 

 for practical use, by collections of sample 

 cards of the great dyehouses, or by home-made 

 collections of dyed samples, carefully noted 

 and indexed, in order to get a good idea of the 

 color produced by each dyestuff. 



On the other hand, Lehne's large and val- 

 uable book, published in 1893, containing 

 dyed and printed samples of the colors de- 

 scribed in the last Schultz & Julius catalogue 

 of that time, was so exceedingly difficult and 

 expensive to prepare that it has proved im- 

 possible to keep it up to date. 



But, by using these very excellent color 



