JO- 



NA TURE 



[February 5, 1903 



studied the question on the spot, except de Saussure,' who was 

 there some thirty years ago. He suggested that the swamps 

 which extend between the water and the dry land prevented the 

 creatures from gaining the latter and therefore from transforming. 

 But thick rush-swamps fill only the north-western extent of the 

 region. Then Weismann speculated upon the dismal condition 

 of the salt-incrusted surroundings which were supposed to have 

 hemmed in the Axolotl. This dream could apply only to Lake 

 Texcoco, where there are none ! The latest suggestion has been 

 made by Herrera,'- the professor of zoology in Mexico. He puts 

 it categorically that the Axolotl cannot transform for want of 

 food. Fancy the idea that overcrowding of the lakes, which 

 are teeming with food, causes famine and at the same time pro- 

 duces big, oily, fat Axolotl ! 



The inducements to remain in the water, their birthplace, have 

 become too strong for the larvoe to yield to their innate tendency 

 of further development. Nothing is stunted in their bodies. On 

 the contrary, they become to a certain extent overgrown, and the 

 sexual organs, which anyhow in most terrestrial Urodela are 

 active only during the temporary aquatic life, undergo their 

 normal course of development and function. II. Gadow. 



I 



ISOMERIC CHANGE IN BENZENE 

 DERIVATIVES? 



N recent years, it has become realised that in many chemical 

 reactions, isomeric changes — that is, the change of a given 

 substance into another of identical composition, but possessing 

 a different and under the conditions a more stable constitution — 

 play an important part ; thus, as is well known, from the salts 

 of certain organic acids, the acid frequently cannot be obtained, 

 but a neutral isomeride (the pseud j-acid) into which the acid 

 changes is alone isolated. One very interesting instance of 

 isomeric change is to be found in the process of substitution in 

 certain benzene derivatives. As long ago as 1S87, Armstrong 

 suggested that the ready production of para-derivatives from 

 amino- and hydroxy-aromatic compounds — anilines and phenols 

 — was due to the formation initially of isomeric compounds in 

 which the amino- or hydroxylic hydrogen was displaced by the 

 substituting group. Since that date, these labile precursors 

 (phenyl chloramines, nitramines, &c.) of the ordinary substitu- 

 tion products (chloro-, nitro-anilines, &c.) have been isolated 

 in numerous cases. They can always be transformed into the 

 stable isomeride, but this change seems to be conditioned by the 

 presence of some other substance — the catalyst. As Armstrong 

 has suggested, these isomeric changes are "fermentative" in 

 character, often taking place with great facility and under the 

 influence of minute amounts of the catalyst. Measurements of 

 the velocity show that changes of this type are always apparently 

 monomolecular (that is, each molecule changes per se) ; but such 

 a result only proves that the slowest reaction is monomolecular 

 and does not exclude the possibility of the simultaneous occur- 

 rence of other more rapid transformations, which form part of 

 the complete change. 



A most instructive example of isomeric change is found 

 amongst diazobenzene derivatives. The diazobenzene salts are 

 derived from the base, diazonium hydroxide, to which is now 

 generally assigned the expression Ph.N(OH) = N. On treat- 

 ment with alkalis, this base is converted into the salts (diazo- 

 tates) of an isomeric acid, to which the formula Ph.N:N.OH 

 is given. On attempting to isolate the acid from these salts, a 

 neutral isomeric substance (the pseudo-acid) is obtained ; this 

 is probably a phenylnitrosamine, Ph.NH.NO. In this paper, 

 the author describes a new case of intramolecular change of a 

 remarkably interesting kind : — Chloro- and bromo-henzene- 

 diazonium hydroxides, C (1 H,X.,.N(OH) = N, readily change into 

 isomeric hydroxybenzene derivatives, C,;H._.\.,(OH).N.\ =N, 

 the hydroxyl group and one of the halogen atoms (an ortho- 

 placed halogen atom) having exchanged positions. This change 

 not only affords another illustration of the transference of a 

 group from the side chain of an aromatic compound into the 

 benzene nucleus, but further shows the tendency, which has 

 been occasionally noticed, for an ammonium base to change into 



1 Verhandl. Schweizernatitrforsch. Gesellsck. Einsiedcln (1868), p. 89. 



- La Naturaleza. 2nd ser., vol. iii. 'May, iqoo). 



;: Abstract of paper on " Isomeric Change in Benzene Derivatives—The 

 Intr'n hange of Halogen and Hydroxyl in Benzenediazonium Hydroxides." 

 By Dr. K. J. P. Orton. Read before the Royal Society December 4, 1902. 



NO 1736, VOL. 6"/~] 



an isomeric substance of neutral character. Under all con- 

 ditions, when it is possible for the diazonium hydroxide to be 

 present, the wandering of the hydroxyl group takes place. 

 Thus in dilute aqueous solution of such diazonium salts as the 

 nitrate or the hydrogen sulphate, the small quantity of diazonium 

 hydroxide which arises from hydrolytic dissociation undergoes 

 this change. In the presence of excess of acid, there is no 

 hydrolytic dissociation and consequently the isomeric change 

 does not take place. In the case of the salt of a weak acid, as 

 the acetate, where the hydrolytic dissociation is considerable, 

 the rate of interchange of halogen for hydroxyl is greatly in- 

 creased. In the naphthalene series, this intramolecular change 

 occurs with even greater ease and rapidity than in the benzene 

 series. 



The elucidation of the nature of the process by which halogen 

 is eliminated from diazobenzene compounds (a reaction first 

 observed by Meldola in the naphthalene series) has rendered 

 possible the removal of certain errors in the statements regarding 

 the changes undergone by diazonium compounds. Thus 

 Hantzsch has recently stated that j--tribromobenzenediazonium 

 hydroxide, C 6 H„Br :l .N(OH)rEN, changes into the correspond- 

 ing phenyl nitrosamine, QILBr.,. NIL NO, not realising that 

 under the conditions (presence of acetic acid) an isomeric change 

 has taken place, bromine being eliminated. 



A DAYLIGHT PHOTOMETER. 



A " DAYLIGHT PHOTOMETER " described by Mr. A. H. 

 -^ Munsell, of Boston, Mass., is designed mainly for the 

 comparison of the brightnesses of various coloured surfaces 

 illuminated by daylight or artificial light. The instrument con- 

 sists essentially of two " cat's-eye " shutters placed symmetri- 

 cally towards a source of diffused light. Through one of these 

 the light falls on the coloured surface to be tested, through the 

 other upon a standard white surface. The second shuttei is 

 then gradually closed until the resulting grey produced on the 

 white screen just matches the coloured surface in intensity, 

 whilst a dial connected with this shutter shows, in percentage, 

 how much darkening has been necessary to match the coloured 

 surface under test. The instrument has also been applied to 

 the testing of light transmitted through coloured media. 

 Owing to the wide variation in the sources of light used, as 

 well as in the colour perceptions of different observers, no 

 degree of absoluteness can be attached to the readings. As 

 Purkinje and Dove showed, the relative brightness of two 

 differently coloured surfaces changes as the strength of the 

 illuminating source is altered. But although the readings of 

 the instrument must for these reasons be interpreted with great 

 caution, the arrangement seems capable of supplying much 

 interesting information on the variations of colour perception 

 under different conditions. Albert Campbell. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — It was agreed by the senate on January 20, 

 by a large number of placets to one non-placet, to appoint 

 two additional demonstrators of human anatomy. 



The funeral service for the late Master of Caius, Dr. 

 X. M. Ferrers, F.R.S., took place privately in the college 

 chapel yesterday, February 4. The public service for the 

 late Sir G. G. Stokes, F.R.S., Master of Pembroke, is to 

 b". held in St. Mary's Church to-day, and will be attended 

 by a large number of members and officers of the University 

 and representatives of learned societies. 



By the will of lb.- late Mr. F. J. Quick, of Trinity Hall. 

 the residue of his estate, valued at some 50,000/., is placed 

 in trust for the promotion of study and research in vegetable 

 and animal biology. The University is to draw up a scheme 

 for the administration of the trust, wherein it shall be pro- 

 vided that no office or appointment paid from the income 

 of the fund shall be held by the same person for more tharr 

 three years without being thrown open for a fresh election. 



The' election to the Lucasian professorship, vacant by the- 

 death of Sir G. G. Stokes, will take place at noon on 

 February 28. The electors are the heads of colleges. 



Miss i. Sollas, Newnham College, has been nominated to 



