306 



SCIENCE 



[N. S. Vol. XXVII. No. ( 



edge found in the works of Shakespeare. The 

 volume closes with a biographical and critical 

 estimate of Descartes, and a similar account 

 of Eobert Mayer, his life, and the trials which 

 he experienced in the promulgation of his 

 views on energy. 



The same wide knowledge of curious 

 matters pertaining to science pervades the 

 briefer articles, even the titles of which can 

 not all be quoted. Saint Augiastin on quick- 

 lime, the superstitions connected with the 

 mandragora, the mystery of the " coasts of 

 Bohemia " (Winter's tale), which is solved by 

 a remark encountered while reading for his 

 "History of Sugar," are all delightful. A 

 note on Who introduced the experiment of 

 burning of a watch spring in oxygen, shows 

 that it was Jan Ingen-Housz (1730-1799), 

 better known as the discoverer of the fact that 

 plants breathe oxygen and generate carbonic 

 acid, in addition to assimilating the latter as 

 food. Amongst the other papers are interest- 

 ing biographies of Marggraf and Achard, and 

 a curious report on the profits which Edward 

 Howard (brother of the Duke of Norfolk) 

 derived from the invention of the vacuum 

 evaporating apparatus. Several articles deal 

 with subjects connected with sugar. But the 

 author is more than a sugar-chemist and his 

 book can be recommended most heartily to all 

 who are interested in the history of science. 

 Alexander Smith 



The University of Chicago 



Die Zustandsgleichung der Gase und Flilssig- 

 heiten und die Eontinuitatstheorie. Von 

 Professor Dr. J. P. Kuenen in Leiden. 

 Braunschweig, F. Vieweg und Sohn. 1907. 

 Pp. x; -1-241. 



Professor J. P. Kuenen, now at Leyden, and 

 recently at University College, Dundee, is a 

 man whose experience has peculiarly fitted 

 him for the task of writing this book, as might 

 be inferred from an examination of the book 

 itself. The "equation of state" which was 

 devised by J. D. van der Waals, of Amster- 

 dam, in 1873, and which bears his name, is an 

 equation which attempts to give in a compact 

 form, the laws controlling the variations of 

 volume, pressure and temperature of all gases. 



not only when they are far removed from the 

 critical condition, but even at and near the 

 critical point as well. It is usually written 



{p + a/v-) {v — i) =BT 



where a, b and B are constants for any one 

 gas, and p is the pressure, v the volume of 

 unit mass, or specific volume, and T is the 

 absolute temperature of the gas. This equa- 

 tion is a vast improvement over anything that 

 preceded it, particularly the equation of so- 

 called perfect or ideal gases, representing 

 Boyle's and Charles's laws, and is a landmark 

 in the history of physics, but it nevertheless 

 does not represent the facts with complete suc- 

 cess. It seems indeed as if it must always 

 remain impossible to represent by one equa- 

 tion containing only a moderate number of 

 constants, the complexity of real gases, for 

 real gases are simple only when compared with 

 liquids or solids, or when their complexities 

 are overlooked, and we regard merely their 

 most important characteristics. The equation 

 has, however, been of marked service in show- 

 ing the relation between different gases, and 

 between various phenomena of gases, particu- 

 larly those connected with their behavior when 

 near the critical point, and when they depart 

 most from the simple laws of ideal gases. 



Professor Kuenen's book begins with a gen- 

 eral statement of the phenomena attending 

 the condensation of gases into liquids. He 

 shows how the elementary kinetic theory of 

 gases explains their behavior when far above 

 the critical point. He then shows, following 

 van der Waals, how this simple theory may 

 be modified by a consideration of the finite 

 size of the molecules of a gas and the forces 

 of attraction which may exist between them. 

 The equation of state having been obtained, 

 it may be used to throw considerable light on 

 the phenomena of condensation, conditions of 

 unstable equilibrium, etc. Several chapters 

 are devoted to what is perhaps the most im- 

 portant thing to be considered, the agreement 

 between the equation and experimental facts. 

 In these chapters are considered the law of 

 corresponding states, critical constants, be- 

 havior at high pressure, saturation pressures, 

 Joule-Kelvin researches, specific heats, etc. 



