76ft Scientific Intelligence. 



Inc. ) . — This is the second edition of an excellent text-book which 

 first appeared five years ago. By means of a thorough revision 

 and considerable amplification the present edition has been made 

 to give a very satisfactory view of the recent advances in physical 

 chemistry. The radioactive phenomena bearing upon our present 

 atomic theory are well presented as is also the bearing of X-ray 

 spectra upon crystalline structure, while the chapter on colloids 

 has been re-written. The book gives a very clear and able 

 account of theoretical chemistry, and the practical problems 

 introduced at the conclusion of many of the chapters should be 

 found very useful in connection with the study of the subject. 



h. l. w. 



5. Electro- Analysis; by Edgar F. Smith. 12mo, pp. 344. 

 Philadelphia, 1918 (P. Blakiston's Son & Co.).— This is the sixth 

 edition of a work so well known and highly regarded among 

 analytical chemists that no description of its general features 

 need be given. Since the appearance of the last edition com- 

 paratively few important advances have been made in this line 

 of work, so that comparatively few additions to the text have 

 been required. Among the more important additions is the 

 description of an improved double cup for the purpose of analyz- 

 ing mixtures of halides, which has been perfected in the author 's 

 laboratory. It is believed that all the recent advances, that may 

 be considered reliable have been brought into the new edition. 



h. l. w. 



6. Absorption of X-Rays in Aluminium and Copper. — A 

 method for determining the coefficient of absorption of X-rays 

 in elements, which seems to eliminate the chief sources of error 

 (heterogeneity and variations in intensity of the radiations) 

 usually affecting the results, has been devised and tested by 

 C. M. Williams. 



In order to obtain a homogeneous beam the rays from a Cool- 

 idge tube were analyzed by a rock-salt ' ' grating. ' ' The inclusion 

 in the first-order beam of shorter wave-lengths of higher orders 

 was prevented by using too low a voltage to excite the submul- 

 tiple radiations. In the paper, lines are plotted with thickness 

 of absorber as abscissa and logarithm of ionization current as 

 ordinate, each line corresponding to a different applied voltage. 

 The length of the alternative spark-gap, between polished metal 

 spheres 1 cm. in diameter, was taken as a measure of the voltage. 

 The lines for 12, 9, and 6 cms. spark-gap show decided curvature 

 and hence superposition of several wave-lengths. The line for 

 3 cms. is, on the other hand, perfectly straight thus indicating 

 a homogeneous beam. 



In order to compensate for the fluctuations in intensity of the 

 source a special form of ionization chamber was constructed. 

 The innovation consisted in separating the ionization chamber 

 into upper and lower halves or compartments by a horizontal, 



