142 SCIENCE PROGRESS 



ment. The larger and more specialised pieces of apparatus are practically 

 confined to the centrifuge, the ultrafilter, and of course the microscope, 

 preferably with an ultracondenser in addition. 



No doubt as time goes on practical work in colloid chemistry will go 

 beyond the limits set by the present form of Mr. Hatschek's manual. It 

 would add considerably to its value if the second edition were to contain 

 some directions for carrying out in as quantitative a manner as possible a 

 determination of the rate of coagulation (a subject still very undeveloped), 

 some comparative experiments to demonstrate the use of ultrafilters, some- 

 thing on endosmose, and a few additional notes on cataphoresis, e.g. the 

 necessity of using a medium of the same conductivity as that of the sol or 

 emulsion, to maintain constant potential gradient, and the meaning of the 

 iso-electric point and its determination. 



The book can be warmly recommended. W. C. McC. Lewis. 



A Course of Practical Chemistry for Agricultural Students. Volume II, Part I. 



By H. A. D. Neville, M.A., F.I.C., and L. F. Newman, M.A., F.I.C.. 

 School of Agriculture, Cambridge University. [Pp. 122,] (Cam- 

 bridge : at the University Press, 1919. Price ^s. net.) 



The exercises presented in this volume form part of a work which when 

 complete will cover the whole of the practical course in agricultural chem- 

 istry for students taking the degree in agricultural science at Cambridge. 

 This whole work will be complete in three volumes. Volume I will deal 

 with the chemistry and physics of the soil, and will cover the first year's 

 course. The second year's course on the chemistry of foods is provided for 

 by Volume II. This is to be issued in two parts: the first part, that here 

 considered, deals with the qualitative aspect of pure organic chemistry as 

 far as it is essential for agricultural students ; while the second part, not yet 

 issued, will deal more closely with quantitative determinations and analyses 

 of foods. Volume III will deal with more specialised matter, such as the 

 chemistry of fungicides and insecticides, and food preservatives. 



The chemistry in the volume under review here is entirely qualitative. 

 The subject-matter includes exercises on the simpler organic groups of sub- 

 stances : alcohols, with phenols ; aldehydes, ketones and acids ; esters, amides 

 and amines ; and carbohydrates and proteins. There are also sections 

 devoted to the questions of purification of organic compounds, enzyme action 

 and the determination of the class to which an organic substance belongs. 



After the exercises given in each section of the book a number of notes 

 are added in order to make clear the experiments described in the exercises. 



About one-third of the book consists of blank leaves on which the 

 student can add additional exercises or notes. The value of this provision 

 is obvious to anyone who has had experience of practical classes. 



There can be no doubt of the value of this book to classes in agricul- 

 tural chemistry, and the complete work will obviously become the standard 

 laboratory manual in this subject of ever-increasing importance. 



W. S. 



Practical Physiological Chemistry. By Sidney W. Cole, M.A. [Pp. 

 xvi-H4oi.] Fifth Edition, completely revised and enlarged. (Cam- 

 bridge : W. Heffer & Sons, 1919. Price 15s. net.) 



The fifth edition of this well-known book has been so completely revised and 

 enlarged as to be almost a new book. Three fresh chapters have been added 

 to the earlier portion of the book, so that instead of starting with the pro- 

 teins, the first chapter is now devoted to the properties of solutions ; follow- 

 ing on a description of the general properties of colloids comes the only 



