470 x Scientific Intelligence. 



The course of analysis given appears to be very satisfactory. 

 It is an excellent feature that many experiments are given 

 where the student is compelled to find for himself what happens, 

 as the results are not described. It is noticeable that the book 

 gives very few chemical equations, but it is expected that 

 students shall write each reaction. At the end of the book is a 

 long list of questions, many of which are very excellent for mak- 

 ing the student think, but, as the authors admit, some of them 

 are rather difficult for the average beginner. h. l. w. 



5. The Chemistry and Manufacture of Hydrogen; by P. 

 Litherland Teed. 8vo, pp. 152. New York, 1919 (Longmans, 

 Green & Co., price $3.40 net). — We find here a very clear and 

 interesting monograph on hydrogen gas, the use of which has 

 enormously increased in recent years, not only in connection 

 with balloons and air ships for war purposes, but also for use 

 in the hardening of oils and in the direct combination with 

 nitrogen to form ammonia according to the Haber process. 



The book takes up the uses, discovery, occurrence in nature 

 and chemical properties of hydrogen, then it deals very thor- 

 oughly and satisfactorily with the manufacture of the gas by 

 chemical, chemico-physical and physical methods. Numerous 

 drawings illustrate the pieces of apparatus, many patents are 

 referred to, and much other useful information is given. The 

 book may be recommended to all who desire to understand this 

 important industry. . h. l. w. 



6. Calculation of the Radiation Constants c 2 and a. — The 

 theory of series spectral lines first developed by Niels Bohr has 

 been improved and extended by Sommerfeld. The more com- 

 plete form of the theory has also been tested, by Paschen, on 

 the spectra of hydrogen and helium, and found to be verified 

 in the minutest details. After the empirical determination of 

 a universal constant a and of a constant B characteristic of each 

 gas, the theory gives not only an accurate representation of the 

 series spectra of both gases, but it also furnishes an explanation 

 of the detailed structure of the discrete lines as well as a clue 

 to the intensity ratios of the separate components of the lines. 

 Furthermore, on the basis of the theory, accurate values for the 

 specific charge of an electron and for Planck's quantum con- 

 stant h have been computed from B ± and B 2 . (The subscripts 

 1 and 2 refer respectively to hydrogen and helium.) Since the 

 theory is extremely reliable, — at least when applied to the gases 

 just named, — and as an exceptionally high degree of accuracy 

 can be attained in the measurement of wave-lengths, it may be 

 expected that other physical quantities derived from the theory 

 and spectroscopic data will also be very dependable. 



The radiation constants c 2 and <x have been computed, in the 

 manner suggested, from the values of B x and B 2 by F. Henning : 

 c 2 occurs in the numerator of the exponent of the Napierian 



