Chemistry and Physios. 295 



in showing that the additive values used by Kopp for carbon and 

 hydrogen were incorrect, and in pointing out the effects of vari- 

 ous structures upon the volumes of the atoms. The conclusion 

 has been reached that no physical property is so well adapted to 

 elucidate the ring structure of a compound as the molecular vol- 

 ume, so that it is to be hoped that this will henceforward take its 

 legitimate place as an instrument of research. The book is of 

 much interest to both physical and organic chemists, h. l. w. 



4. A Handbook of Colloidal Chemistry ; by Wolfgang 

 Ostwald. 8vo, pp. 278. Philadelphia, 1915 (P. Blakiston's 

 Son & Co. Price $3 net). — The first edition of this book in 

 English has been translated in a very satisfactory manner from 

 the third German edition by Dr. Martin Fischer with the 

 assistance of Dr. Ralph E. Oesper and Dr. Louis Berman. As a 

 frontispiece there is an interesting portrait of the English chem- 

 ist Thomas Graham, who first distinguished colloids as a class of 

 substances and who coined the word. The important recent 

 growth of this branch of chemistry is well shown in this book, 

 and the subject is treated in a very full and satisfactory manner. 

 The work cannot fail to be interesting and useful to all classes of 

 chemists and physicists. h. l. w. 



5. The Critical Temperature of Mercury. — J. Koenigsberger 

 concluded from his experimental work that the critical tempera- 

 ture of mercury is about 1270° C. Since this investigation has 

 been criticized adversely as giving too low a value, the problem 

 has been taken up anew by Julie Bender at the suggestion of 

 Koenigsberger. The general method consisted in determining 

 the vapor pressure of mercury at high temperatures while the 

 total volume of the liquid and vapor was kept constant. The 

 mercury was sealed in capillary tubes made of the purest fused 

 quartz and the temperatures were determined by the aid of a 

 thermopile. An estimate of the critical temperature was obtained 

 in two different ways. 



The first plan was to observe the changes in volume (or length) 

 of the thread of liquid for different " fillings " and for various 

 temperatures up to 1400° C. By a " filling" is meant the ratio of 

 the volume of the liquid phase present to the total volume of the 

 inside of the capillary cylinder. When fillings are plotted as 

 abscissas and the corresponding temperatures as ordinates one 

 curve is obtained for each initial filling, and all of the curves 

 possess the general characteristics of the so-called Bragg ioniza- 

 tion curves. That is, with rising temperature the filling first 

 increases, then passes through a point of inflection to a maximum, 

 and finally decreases. The most significant properties of these 

 curves are that they become practically straight lines above their 

 maxima— up to the highest temperature (1400° C.) at which 

 observations with silica tubes could be made with sufficient 

 accuracy — and that the extensions of the rectilinear portions con- 

 verge toward one another so as to include between their extreme 

 intercepts on the axis of ordinates the interval 1650°-1700° C. 



