— 150 — 



of a precisely similar freshly-prepared mixture. It was found that peroxide 

 of hydrogen causes a pronounced alteration in geraniol, menthol, menthyl 

 acetate, peppermint oil, and cinnamic aldehyde; that it effects a less pro- 

 nounced change in carvacrol, eugenol, geranium oils, clove oil and terpineol, 

 and that it leaves unaffected anethol, Russian anise oil, bornyl acetate, 

 eucalyptus oil, Siberian pine-needle oil, star anise oil, and thymol. 



Bibliography. 



Those who desire to acquire a knowledge of the nature of refraction, 

 as well as of the coefficient of refraction (the latter being an important 

 factor in the examination of the separate constituents of essential oils) 

 will find in the Refraktometrisches Hilfsbuch lately published by Veit § Co., 

 Leipzig (1911), an excellent guide. In the introduction to the work, the 

 authors, Prof. Dr. W. A. Roth and Dr. F. Eisenlohr, who are known by their 

 researches in the domain of the determination of chemical constitution 

 by physical means 1 ) explain the meaning of the terms "coefficient of re- 

 fraction" and "molecular refraction", after which they deal with dispersion 

 and its cause. In the following chapters they treat of the principles of 

 refractometry and describe in detail the various refractometers. An im- 

 portant section of the book consists of chapters on the development of 

 molecular refraction and dispersion as well as on exaltation and specific 

 exaltation. Want of space forbids us from entering into details on the 

 abundance of interesting material in the book, but we cannot omit to 

 mention that it contains an exact guide to the determination of specific 

 gravity by means of various pycnometers and at different temperatures 

 as well as many tables, including logarithm-tables up to the fifth decimal, 

 which greatly facilitate calculations. 



Analytical Notes. 



The passage in our Report of October 1911 (p. 119) relating to 

 ). Herzog's suggestions on the subject of the test for chlorine compounds 

 in benzaldehyde has caused that author to make a reply 2 ) in which he 

 again lays stress upon the advantages of the modification proposed by 

 him, and in which he leaves it to his fellow-chemists whether they will 

 adopt his method or ours. 



G. Heyl 3 ) and E. Rupp 4 ) have also intervened in the discussion c^; 

 this subject. Heyl recommends the lime-test for chlorine, which he carries 

 out as follows: — 



*) Comp. Report October 1910, 164, 167; October 1911, 122. 



2 ) Berichte d. deutsch. pharm. Ges. 21 (1911), 536. 



3 ) Apotheker Ztg. 27 (1912), 49. 



4 ) Ibidem 92. 



