Chemistry and Physics. 217 



4. The Volumetric Determination of Cerium by Means of 

 Potassium Permanganate. — Victor Lenher and C. C Meloche 

 have studied method, which, although it has been known for a 

 long time, has not been accurately described in connection with 

 the conditions required for accuracy. In a neutral solution the 

 following reaction may be expected to take place : 



3Ce(N0 3 ) 3 + KMn0 4 + 2H,0 = 



2Ce(NO s ) 4 + Ce(OH) 4 + KNO, + Mn0 2 



Then the eerie nitrate undergoes hydrolysis, setting nitric acid 

 free, so that the reaction tends to become reversible : 



Ce(N0 3 ) 4 + 4H,0 = Ce(OH) 4 + 4HN0 3 . 



Hence in order to obtain a complete reaction this free acid must 

 be neutralized in a proper manner. However, if a cerous solution 

 is made distinctly alkaline and the solution is either heated or 

 allowed to stand for some time, atmospheric oxygen is absorbed 

 to such an extent that subsequent titration necessarily gives low 

 results. The authors have tried a considerable number of methods 

 for neutralizing the liquid during the titration, and have found 

 zinc oxide or magnesium oxide added in excess in the form 

 of paste to be the best reagents for the purpose. In the case of 

 the use of zinc oxide the titration may be begun in the cold and 

 finished hot, or the whole titration may be performed at a boiling 

 temperature. When magnesium oxide is used it is best, in order 

 to prevent air oxidation, to nearly finish the titration before 

 adding the oxide. The results obtained by the authors, using 

 from 0*16 to 0-3 g. of cerium in about 110 cc of solution, were very 

 satisfactory. — Pour. Amer. Chem. Soc, xxxviii, 66. h. l. w r . 



II. Geology and Mineralogy. 



1. Men of the Old Stone Age : their Environment, Life and 

 Art; by Henry Fairfield Osborn. Pp. xxvi, 545, with 8 

 plates and 268 text figures. New York, 1915 (Charles Scribner's 

 Sons). — This very valuable treatise is a fitting associate of Pro- 

 fessor Osborn's other great book, The Age of Mammals (1910), 

 and in comprehensiveness of treatment brings to mind Obermaier's * 

 Per Mensch der Vorzeit (1913). No organic being has been 

 more studied than man, living and fossil, and because of the 

 many wonderful finds of the bones and implements of his ances- 

 tors in Europe and Asia, going back to the ape-man of Java, 

 there is at present a great wealth of papers and books on this 

 intricate and difficult subject. 



There are four ways of determining the chronogenesis of man: 

 by geology, paleontology, anatomy, and human industry. " Geo- 

 logic events mark the grander divisions of time; palreontologic 

 and anatomic events mark the lesser divisions; while the succes- 

 sive phases of human industry mark the least divisions" (19). 



Am. Jour. Sci. — Fourth Series, Vol. XLI, No. 242. — February, 1916. 

 15 



