488 SCIENCE PROGRESS 



brilliantly conflrmed by Siedentopf and Zsigmondyin 1903, that the ultimate 

 particles of bodies in the colloidal condition are aggregates. It seemed 

 improbable that the stoichiometrical laws of classical chemistry should apply 

 to a state in which specific surface appeared to be a predominating factor. 

 Consequently, colloid chemistry has been treated as a separate subject in which 

 the classical laws were replaced by Freundlich's empirical adsorption law and 

 the Hofmeister series. Exceptions to the adsorption law were found , and it 

 might have been thought significant that every property of true solutions 

 is affected by series of anions and cations similar to those that have played so 

 important a part in the theory of colloids. But suggestions made from time 

 to time that colloids should not be regarded as exempt from the laws of 

 chemistry have not been well received. 



The book before us is revolutionary in character. Prof. Loeb gives an 

 account of a brilliant series of experiments which indicate that the 

 amphoteric proteins combine stoichiometrically with acids and alkalies. 

 The Hofmeister series is then explained by the fact that different acids, 

 alkalies, and salts have different effects on the pH of protein solutions. 

 When this is allowed for, the only effect is that of valency, and all the properties 

 of proteins, their osmotic pressure, swelling, P.D. viscosity, and stability, 

 can be explained mathematically on the basis of the Donnan equilibrium. 



As the result of v. Weimarn's experiments we have abandoned the 

 division of substances into two separate classes of crystalloid and colloid. 

 Now it seems incorrect to discriminate between crystalloidal and colloidal 

 solutions, or to regard the science of colloids as a water-tight compartment of 

 physical chemistry. 



On p. 46 the argument is a little difficult to follow. And on p. 131 it would 



y ^ 



have been clearer to use the term -, as on p. 125, instead of -. Otherwise, 



X y 



as would be expected, the book is clearly written and practically free from 



misprints. It is a work that will survive much criticism and must be read 



by everyone seriously interested in colloid chemistry. 



S. C. B. 



Chemistry and its Uses. A Textbook for Secondary Schools. By W. Mc- 

 Pherson and W. E. Henderson. [Pp. viii + 447, with 260 illustra- 

 tions.] (London and New York : Ginn & Co. Price 7s. 6d. net.) 



This is a typical American secondary-school textbook, and as such has a 

 special interest for the English secondary-school teacher. The point of view 

 from which the subject is dealt with is very different from that of the average 

 English school teacher, who tackles his subject either from the academic 

 point of view as a pure science, or from that of the educationist, as a means 

 of mental training, or perhaps most commonly from a compromise between 

 these two. The textbook before us, however, has obviously been written 

 with a view to giving the student some knowledge of chemical processes in 

 their relation to daily life, a characteristic attitude of all American school 

 teaching, and, in some degree, one from which we English teachers can well 

 afford to learn. For this reason we welcome this book and strongly recom- 

 mend it to English school teachers of science. It might well be used as a 

 supplementary reader in the upper classes, and if the book served no other 

 purpose, it would at least give added interest to the study of the subject by the 

 pupils themselves. 



One notices also, in the exercises particularly, the tendency in the American 

 schools to make the pupils study their textbooks for themselves, without 

 expecting so much aid from their teachers. The illustrations are very good 

 and will prove of great value in explaining the modern developments of 

 applied chemistry. 



W. C. B. 



