November 



f, I 



900] 



NATURE 



that theoretically possible being 70 per cent. Von 

 Baeyer also showed that, by acting upon ortho-nitro- 

 cinnamic acid with caustic soda and chlorine, ortho-nitro- 

 phenylchlorolactic acid was produced, which on treat- 

 ment with alcoholic caustic potash was converted into 

 ortho-nitrophenyloxyacrylic acid, and this on being fused 

 yields small quantities of indigo. Owing, however, to the 

 high cost of ortho-nitrocinnamicacid, indigo so produced 

 could not enter into competition with the natural dye. 

 In 1882 von Baeyer and Drewson brought out yet another 

 synthesis. They found that, by acting upon a mixture of 

 ortho-nitrobenzaldehyde and acetone with caustic soda, 

 indigo was produced, and, further, if the starting pro- 

 ducts were pure, that the yield of indigo was 80 per 

 cent, of that theoretically obtainable. In 1890 Heumann 

 discovered that when phenyl glycine was melted with 

 ' ' caustic soda, taking care that air was, so far as possible, 

 t excluded, a yellow-coloured fuse was obtained. This 

 fuse, on being dissolved in water and exposed to the 

 action of the air, produced indigo. 



Unfortunately, although the low price of the materials 

 employed should have caused this to be a successful 

 manufacturing process, the yield of the dye-stuff was very 

 poor. Heumann shortly afterwards showed that a very 

 much better yield could be obtained by employing 

 phenylglycine-ortho-carboxylic acid, but although the 

 yield was better the cost of production was higher, the 

 more expensive anthranilic acid taking the place of the 

 cheaper aniline as a starting product. Of late, however, 

 the price of anthranilic acid, owing to improved methods 

 of manufacture, has fallen very considerably, and, doubt- 

 less, will continue to fall. Indigo can also be obtained 

 by fusing bromacetanilid with caustic potash, the indol 

 so produced being oxidised by the action of the air to 

 indigo. Again, when ortho-nitroacetophenone is care- 

 fully heated with zinc dust, a sublimate of indigo blue is 

 obtained. There are many other syntheses of indigo 

 known, but the majority of them are of more theoretical 

 than practical importance. 



Of the many methods for obtaining artificial indigo, 

 only two or three modifications are employed for manu- 

 facturing the dye. These are von Baeyer's ortho-nitro- 

 benzaldehyde and aceton synthesis, and that of Heumann 

 from o-phenylglycinecarboxylic acid. But beside indigo 

 itself there is a substance sold under the name of 

 '• indigo salt," which is the sodium bisulphite salt of the 

 methylketone of o-nitrophenyl-lactic acid. It is readily 

 soluble and is used for indigo printing. 



Artificial indigo as brought into the market contains 

 over 90 per cent, of indigotin, whereas in the natural 

 product the quantity varies from 20 to 90 per cent. The 

 artificial product, however, contains no indigo-red, indigo- 

 brown, or indigo-gluten ; whereas these substances are 

 present in natural indigo, and exert an influence in dyeing 

 certain shades of indigo. Indigo itself cannot be em- 

 ployed for dyeing owing to its insolubility. But when 

 subjected to the action of reducing agents it is converted 

 into indigo-white^ which is soluble in alkalis. Wool or 

 cotton dipped into such a vat and then exposed to the 

 action of the air become dyed a fast blue. 



One would have supposed that the indigo producers 

 would have taken warning from the extinction of the 

 artificial alizarin industry, and called to their aid experi- 

 enced agriculturists to see if it were not possible to 

 increase the yield and quality of the indigo plant, and 

 chemical experts to endeavour to improve the process of 

 manufacture. This, however, has not been done. The 

 planter appears uncertain whether thick or thin seeding 

 is the better, whether any other manure except seet 

 should be employed. Again, whether the seet should be 

 applied to the land fresh or whether it should first be 

 allowed to ferment. The manufacturing is entirely con- 

 ducted by "rule of thumb." It is a matter of dispute as 

 to whether the bundles of indigo plant should be packed 



NO. 161^, VOL. 63] 



tightly or loosely in the vats. If the water employed 

 should be hard or soft is purely a matter of individual 

 opmion. Again, it is a question of debate as to how 

 long the cut plant should be steeped, &c. The Badische 

 Anilin Soda Fabrik is said to have invested 500,000/. in 

 plant for the manufacture of artificial indigo. Will 

 British (Indian) manufacturers never lay out capital in 

 scientific investigation .? Will they never realise that 

 money so laid out is almost certain in the near future to 

 bring in a rich return ? In conclusion, I give the follow- 

 ing quotation from the report on the trade of Frankfurt 

 for^i899, by Consul-General Sir Charles Oppenheimer :— 

 " In the territories in which natural indigo is grown, 

 the intensity and magnitude of the danger which lies in 

 the advance of the artificial product ought not for a 

 moment to be disregarded. The struggle between arti- 

 ficial and natural indigo has already commenced. The 

 latter still shows some advantages, inasmuch as its bye- 

 products, such as indigo gluten, indigo red, &c., aid the 

 dyeing process to some extent. If natural indigo is to 

 retain its position, every effort must be directed in a 

 rational manner to organising its culture towards the 

 manner in which it is collected, and the way the dye is 

 shipped. In order to obtain a favourable result, the 

 ablest experts should cooperate in this important task. 

 To-day the fate of East Indian indigo culture lies un- 

 fortunately in the retorts of the chemical factories." 



F. MoLLwo Perkin. 



THE FORM AND SIZE OF BACTERIA. 



TDACTERIA is a generic term that has been applied 

 -'-' to an extensive group of single-celled organisms 

 belonging to the lowest forms of plant life The bacteria, 

 obtain their nutriment from organic matter, either dead 

 or living, and are therefore capable of leading a sapro- 

 phytic or a parasitic existence. They are amongst the 

 smallest forms of life with which the biologist has to- 

 deal, the transverse diameter of the individual cells 

 seldom exceeding a few micro-millimetres, or it may be 

 a fraction of a micro-millimetre. The highest powers of 

 the microscope are consequently necessary for the study 

 of their structure, which is of a simple character, consist- 

 ing essentially of protoplasm with a containing cell- 

 membrane. The most striking differences are to be 

 found rather in the biological properties of the bacteria 

 as promoters of decomposition, putrefaction and fermen- 

 tation, or as the originators of morbid processes ir» 

 plants and animals, than in any distinctive features they 

 possess as vegetable cells. The following account is 

 simply intended to give the reader who is not a specialist 

 a general conception of the main types of these 

 organisms, which form the special study of bacteriology. 

 It may, in the first instance, be pointed out that 

 though the bacteria are microscopically, minute organ- 

 isms, yet considerable variations in shape and size occur. 

 The illustrations in the accompanying plate have been 

 selected to illustrate these two points. It will be seen 

 that, for example, amongst the most widely known 

 pathogenic organisms the variation in form is consider- 

 able, whilst in point of size the largest of these is many 

 times greater than the smallest. Bacteriology is at 

 present largely dependent for a classification of the 

 bacteria upon the variations that occur in their shape. 

 The individual cells multiply by a process of fission, and 

 the fundamental forms are spherical, oval, rodlike or 

 spiral in shape. At the same time the species cannot 

 be entirely determined by the microscopic appearance. 

 In fact, there are many organisms which it is impossible 

 to identify until other characteristics, such as the macro- 

 scopic appearance of their artificial growth on suitable 

 media, or their pathogenic effects on animals, have been 

 observed. The fact has also to be remembered that a 



