52 



NATURE 



[May 2 I, 1908 



to g^ive us more than a general idea as to the course 

 of reactions. At the same time, it is by no means a 

 subject which can be dismissed as being useless, be- 

 cause a very great deal of help may at times be ob- 

 tained by the study of thermochemical data. For 

 example, in manufacturing operations, it is of the 

 first importance to know heats of combustion, because 

 the number of calories required to decompose a sub- 

 stance is of course a guide to the manufacturer in 

 connection with the energy required in a given process. 



Quite recently Prof. J. W. Richards contributed 

 a very useful and interesting series of papers in ar 

 American technical journal upon the thermochemistrj 

 of metallurgical processes. Furthermore, the subject 

 is of great importance to the electrochemist, who is 

 able to determine the voltage necessary to be em- 

 ployed in an electrolytic process if he knows the 

 heats of combination of the compound. Or we might 

 talce another example. In aluminothermics it is 

 owing to the very high heat of formation of alu- 

 minium oxide that such an enormous amount of heat is 

 given out when aluminium reacts with certain metallic 

 oxides, and consequently one can tell beforehand 

 whether a given oxide will be readily reduced by 

 means of aluminium or not. 



Of all the workers in the field of thermochemistry 

 none has done such thorough, careful, and pioneer- 

 ing experimental work as Julius Thomsen, and it was 

 .•I happy idea of Sir William Ramsay to include a 

 translation of Thomsen's Dutch work in the well- 

 known text-books on physical chemistry which are 

 now finding such an important place in the chemical 

 literature of the country; and we may say at once 

 that Miss Burke has done her part of the work ex- 

 tremely well. As she states in the preface, it has 

 been necessary at times, owing to the advance in other 

 branches of physical chemistry, slightly to alter the 

 reading of certain sentences; for example, taking 

 her own illustration, where Thomsen has used the 

 (expression " Neutralisation is regarded as a union 

 (if acid and base, with formation of water," Miss 

 I>urlve has changed this to " Neutralisation is re- 

 garded as a union of acid hydrogen and basic hydroxyl 

 to form water." Undoubtedly some chemists will take 

 exception to such an alteration, and will say it is 

 pedantic and unnecessary, particularly those who are 

 not attached to the ionic theory, and, after all, there 

 arc a goodly number who consider there are many 

 difficulties which require to be cleared up before the 

 ionic hypothesis can be considered fundamental. 



The first portion, the introduction, introduces the 

 subject with an explanation of experimental calori- 

 metric methods, the apparatus being described and 

 illustrated, and the methods of using it fully gone 

 into. Chapter i. deals with the absorption of gases 

 and the heat produced when they, liquids or solids 

 are dissolved in water, and a number of tables are 

 given, with the thermochemical data. The next 

 chapter deals with the rather complicated question of 

 heat of hydration ; the methods of calculation for ob- 

 taining the heat formation of different compounds, 

 provided the heat formation of certain substances is 



NO. 2012, VOL. 78] 



known, are carefully set out throughout the pages. 

 The book not only deals with inorganic com- 

 pounds, but also with a very large rmmber of organic 

 substances, the tables in chapter xii. being exceed- 

 ingly full. .\n interesting part of this chapter is that 

 in which the heat formation of isomeric compounds is 

 given. Thus the difference of heat formation of 

 propyl and isopropyl alcohol is 5'3 cal., that between 

 isobutyl alcohol and trimethyl carbinol being 17-15 cal. 

 In fact, the book deals with Thomsen's work, and 

 will undoubtedly be found extremely useful to an\ 

 investigator who wishes to study this branch of the 

 subject, and as a book of reference to be kept in all 

 chemical libraries, though hardly, we think, for 

 general reading, as it is rather too full for this 

 purpose. F. M. P. 



MA THEM A TIC A L TEX T-B OOKS. 

 (i) The Elements of the Geometry of the Conic. By 

 Prof. G. H. Bryan, F.R.S., and R. H. Pinkerton. 

 Pp. xi + 270. (London : J. M. Dent and Co., 1907.) 

 Price 3*. 6d. 



(2) Geometry, Theoretical and Practical. By W. P. 

 Workman and .\. G. Cracknell. Part ii. Pp. ix + 

 (330-535). (London : W. B. Clive, 1908.) Price 2S. 



(3) Practical Integration for the Use of Engineers, 

 (2~(:. By A. S. Percival. Pp. vi + 86. (London : 

 Macmillan and Co., Ltd., 1907.) Price 2s. 6d. net. 



(4) Integration by Trigonometric and Imaginary Sub- 

 stitution. By C. O. Gunther. Pp. vi + 79. (London: 

 A. Constable and Co., Ltd., 1907.) Price 5^. net. 



(5) A Course in Mathematics for Students of Engineer- 

 ing and Applied Science. By F. S. Woods and 

 F. H. Bailey. Vol. i., .Algebraic Equations, Func- 

 tions of one Variable, .'Xnalytic Geometry, Differen- 

 tial Calculus. Pp. xii + 385. (Boston, New York, 

 Chicago, London : Ginn and Co., n.d.) Price 

 10s. 6(/. 



(i) ' I 'HIS is an attractive little book on geometrical 

 -L conies. The argument is very clear, and 

 presents the subject to a beginner in the simplest 

 possible manner. The difficulty in writing a text-book 

 of this sort lies in the fact that many properties of 

 conies are far more easily treated by analytical than 

 geometrical methods. The authors have met this 

 difficulty by putting first those results which lend 

 themselves more readily to geometrical proofs ; other 

 theorems are left until later on, and then the methods, 

 if not the nomenclature, are analytical. A reasonably 

 large number of examples is given, which are nearly 

 all of a graphical or numerical nature. This is a 

 pleasing innovation, and theoretical examples can be 

 supplied by the teacher, if required, from almost any 

 other text-book. A property of the parabola is dis- 

 cussed at the same time as the corresponding pro- 

 perty of a central conic; much might be said both 

 for and against this course. Many of the proofs are 

 ingenious ; the construction of the hyperbola by means 

 of string and pins alone is worth noticing. A chapter 

 is given in which are discussed those properties of the 

 cycloid, catenary, &c., which can be proved without 

 the aid of the calculus. 



