Chemistry and Physics. 83 



7. Chemie der Eiweisskoerper ; von Dr. Otto Cohnhetm ; 

 Zweite Auflage, Braunschweig. 1904. (Fr. Vieweg und Sohn.)— - 

 The publication, in 1900, of a monograph of three hundred pages 

 devoted to the literature of the chemistry of the proteids empha- 

 sized the importance which the study of this unique and signifi- 

 cant group of compounds has assumed in biological chemistry. 

 The appearance, scarcely four years later, of a new edition of 

 Cohnheim's book, not merely revised but entirely rewritten, gives 

 evidence of the marked progress which has attended recent inves- 

 tigation in this field of study. It is no exaggeration to say that 

 during this interval our ideas regarding the structure of the 

 albuminous bodies have been radically altered in various ways. 

 Investigators and students will therefore welcome the new edition 

 as a useful aid. The judgment which the author has displayed 

 in dismissing with brief reference those theories and facts which 

 no longer possess more than historical interest, and in directing 

 attention to the permanent acquisitions to our knowledge, deserves 

 commendation. From this it will be understood that Cohnheim's 

 book is something more than a mere compilation ; indeed, critique 

 is displayed in every chapter. The more important advances 

 appear in the review of the cleavage products of the proteids 

 and in a discussion of their chemical constitution. The almost 

 unavoidable occasional omissions of reference to important papers 

 are apparently few; and the completeness thus attained gives an 

 added value to the work. l. b. m. 



8. Vapor pressure of Mercury at ordinary Temperatures. — 

 Edward W. Mokxey gives a resume of the work of previous 

 observers of this pressure. The work of Regnault must be dis- 

 missed from consideration, for his experimental means were not 

 sufficiently delicate and precise. Hagen's measurement also must 

 be disregarded because his interpolation formula is inconsistent 

 with what we know of the behaviour of saturated vapors. The' 

 experiments of Hertz, of Ramsay and Young ? agree with those 

 obtained by Morley, while those obtained by Van der Plaats differ 

 widely. A table of vapor pressures is appended to the article. — 

 Phil Mag., June, 1904, pp. 662-667. j. t. 



9. The Penetrating Pays of Radium. — The y-rays of radium 

 have been likened to the X-rays on account of their penetrating 

 power and their not being deflected by a magnet. E. Paschen 

 has made a study of this penetrating power. The rays have a 

 very different absorption-coefficient from the X-rays. The author 

 points out incidentally, that the commonly based method of 

 ionizing the air is not suitable for determining the absorption. 

 The rays lose their power of ionizing the air in passing through 

 layers of lead. The y-rays appear to have a velocity approxi- 

 mating to that of light and they possess great interest ; for we 

 apparently have in their case electrical quantities moving with 

 the velocity of light. — Ann. der Phys., No. 6, 1904, pp. 164- 

 179. j. t. 



