690 



SCIENCE 



[N. S. Vol. XXVII. No. 696 



with, say, a current density of 5 amperes per 

 100 sq. cm. and an E.M.F. of 5.5 volts. Now 

 when a cell is constructed of given dimensions, 

 and fiUed with a solution at a certain concen- 

 tration and temperature, the voltage required 

 to produce a given current density is fixed 

 by the conditions. It is true that the poten- 

 tial faU at the electrode is a very important 

 factor in metal separations but this fall is de- 

 termined directly by the current density. The 

 voltage at the cell terminals is of no conse- 

 quence in the analysis. Prom the directions 

 for each process the prescribed voltage given 

 by the author may be entirely omitted and 

 must be in order to make the directions self- 

 consistent. 



In discussing the various processes the prob- 

 able experimental error is not discussed, but 

 fortunately figures are often given showing 

 the results of actual analyses and from these 

 the probable accuracy of the different methods 

 under favorable conditions may be estimated. 

 Especial attention is given to the deposition 

 of metals on a mercury cathode and to the 

 use of rotating electrodes. The latter device, 

 which permits an analysis formerly requiring 

 several hours to be carried on now in a few 

 minutes, was invented by v. Klobukow in 

 1886 but has only been generally adopted 

 within the last few years. Its eificiency is 

 apparently due merely to the relative motion 

 of electrode and electrolyte which prevents the 

 depletion of the electrolyte in the neighbor- 

 hood of the electrode and also perhaps by 

 mild attrition produces a more coherent film 

 of metal. It is therefore possible to use a 

 very high current density without the forma- 

 tion of loose or poorly adhesive films. 



In the chapter on the history of electro- 

 analysis it is interesting to learn that even in 

 1801 it was proposed to separate the metals 

 by electrolysis, and that in 1860 Lucknow de- 

 posited the metals quantitatively and sepa- 

 rated them from one another by means of the 

 current, and even determined lead and man- 

 ganese by depositing them as peroxides at the 

 anode. 



Besides chapters on the determination and 

 separation of metals there are others on the 

 determination of halogens and nitric acid, on 



electrolytic oxidation and on combustion of 

 organic compounds by electrical heating. 

 There is an index, and each chapter is intro- 

 duced by a short bibliography. The volume is 

 of a convenient size, is bound in flexible 

 covers and is an excellent specimen of book- 

 making. 



Gilbert N. Lewis 

 Massachusetts Institute of Technology 



SCIENTIFIC JOURNALS AND ARTICLES 

 The American Museum Journal for April 

 contains a well-illustrated article by Barnum 

 Brown on " The Trachodon Group " of two 

 mounted skeletons of these strange dinosaurs. 

 There is a plate of the large African elephant 

 head, obtained by the Tader expedition and 

 mounted by Mr. Lang. Under " Ethnological 

 Loan Collections " is a description of the 

 exhibit illustrating the life of the Ojibwa In- 

 dians deposited in a branch of the public 

 library where it is seen by children to whom 

 the story of Hiawatha is told during the 

 " story hour." Recent museum publications 

 are noticed and announcements made of the 

 various lecture courses. 



The Bulletin of the Charleston Museum for 

 March under " Museum Eecords " notes the 

 progress in caring for the collections and tra- 

 cing the history and records of material that 

 has been accumulating for more than a cen- 1 i 



tury and includes " the fossil man of Guade- 

 loupe," the Elliott Herbarium and specimens 

 noted by Holbrook, and Audubon and Bach- 

 man. 



The Evolution of the Elephant, by Eichard 

 S. Lull, forming Guide No. 2 of the Yale 

 University Museum comprises 44 pages, with 

 many illustrations and four maps of distribu- 

 tion of fossil and living forms. It includes 

 a general discussion of the characters and 

 affinities of the Proboscidea, the evolutionary 

 sequence of the genera and species and the 

 indicated migrations of the Proboscidea which 

 led to their present distribution. 



The Museums Journal of Great Britain for 

 March has an article on " Museums of Ele- 

 mentary and Higher Grade Schools," by 



