Chemistry and Physics. 485 



fermentation. The work gives a clear and accurate survey of this 

 very interesting and important department of chemistry. 



h. l. w. 



5. Repertoire des Reactives Speciaux, par F. Jean et G. Mer- 

 cies, 12mo, pp. 121, Paris 1896. — This little book gives the 

 formulae for preparing special chemical reagents which usually 

 bear the names of the originators. The main arrangement is 

 alphabetical according to the names of the authors, while another 

 alphabetical list is given of the substances to be detected. More 

 than four hundred reagents are included, and the book will doubt- 

 less be a convenience to all practical analysts. The value of the 

 work would have been considerably increased if references to the 

 original articles had been given. h. l. w. 



6. The existence of two Orthophthalic Acids. — Considering the 

 great amount of work that has been done with orthophthalic acid 

 by various chemists, the recent discovery by W. T. H. Howe, 

 that this compound exists in two isomeric modifications, seems 

 remarkable. The two acids are identical in composition, mole- 

 cular weight and molecular refraction, but they differ (1) in melt- 

 ing-points, (2) in electrical conductivity, (3) in solubility, (4) in the 

 properties of their salts, and (5) in their reduction-products. The 

 melting-points of the two acids, when finely pulverized, are 184°, and 

 203°. The lower melting acid is converted into the higher simply 

 by boiling the aqueous solution for several hours. The reverse 

 change takes place by boiling a solution in 30 per cent, sodium 

 or potassium hydroxide for some time and precipitating the acid 

 from the cold solution by means of hydrochloric acid. 



The author is inclined to explain the isomerism by a change in 

 the arrangement of the single and double bonds in Kekule's ben- 

 zene ring, as is shown in the following diagrams: 



^<^\ cooh 



COOH 



COOH 



This establishment of a case of two isomeric ortho-derivatives 

 of benzene has an important bearing upon the theory of the struc- 

 ture of the benzene nucleus, for the previous lack of well-estab- 

 lished cases of such isomerism has been considered to be a strong 

 argument against Kekule's celebrated ring formula in its original 

 form. — Am. Chem. Jour., xviii, 390. h. l. w. 



7. On the nature of the X-rays. — D. A. Goldha^jmer states his 

 reasons for believing that the X-rays are ordinary transverse 

 waves of light of which the wave-length are much smaller than 

 the hitherto observed ultra violet rays. Rontgen concluded 

 that the effect observed by him was not due to ultra violet light 

 from the following : 



a. The X-rays suffer no observable refraction in passing from 

 air into water, bisulphide of carbon, aluminum rock salt, glass, 

 zinc, etc. 



Am. Jour. Sci. — Fourth Series, Vol. I, Ko. 6.— June, 1896. 

 32 



