July 15, 1922] 



NA TURE 



71 



and other solvents. The results are used to support 

 the author's theory of the sol-gel transformation, 

 which, according to him, is " a change from what is, 

 at the higher temperature, essentially a solution of 

 soap in water to that which is. at the lower temperature. 

 a solution of waier in soap" The methods of physical 

 chemistry are held to be inapplicable to the latter type, 

 and tin' author is thus relieved of the task of con- 

 sidering the fundamental work of McBain and his 

 school. Various experiments are quoted in support 

 of this gel theory, thus (p. 80) : " A drop of phenol- 

 phthalein solution dropped upon a 10 per cent, 

 sodium stearate water gel remains uncoloured. If. 

 however, the gel is slightly squeezed (which breaks 

 the encircling hydrated sodium stearate film and 

 squeezes out the enclosed solution of soap-in-water), 

 the spot turns bright red." If any one will take the 

 trouble to put a drop of indicator on an acid or alkaline 

 gelatin gel, he will see it turn without squeezing, so 

 that the behaviour of soap gels is not. as the author 

 claims, tvpical or universal, nor is it anv clue to that 

 of protein gels. 



The chapters on proteins are trifling, and analogies 

 like that drawn between the heat coagulation of 

 albumin and the behaviour of a boiled solution of 

 sodium palmitate can scarcely be taken seriously. 

 The author almost throughout dismisses the work of 

 other investigators in the airiest fashion ; must strik- 

 ingly, perhaps, in his chapters on emulsions and froths. 

 Surface and interfacial tensions, adsorption and film- 

 formation are all irrelevant : the decisive factor is a 

 curious and novel physical property of the phases, 

 their " breaking length." An extraordinary feature 

 of the book are the illustrations — half-tones of more 

 than 1300 tubes and bottles containing .soap solutions 

 which, at their worst, convey nothing and, at their 

 best, no more than the text. They may in part 

 account for the high price of the book, which is difficult 

 to explain on any other grounds. 



Commercial Metallurgy. 



The Metallurgy of the Common Metals : Gold. Silver 

 Iron (and Steel), Copper, Lead, and Zinc. By L. S 

 Austin. Fifth edition, revised and enlarged. Pp 

 xviii + 615. (Xew York: J. Wiley and Sons. Inc 

 London : Chapman and Hall, Ltd., 1921.) 425. net 



THE first edition of Prof. Austin's book was pub- 

 lished in 1907— it has now reached a fifth 

 edition. In his preface the author states that since 

 1913, the date of the last edition, such radical changes 

 and improvements have been made in the metallurgy of 

 the common metals that the present book has been 

 NO. 2750, VOL. I io] 



largely rewritten to bring it in accord with present- 

 day practice. It is refreshing to come across a book 

 which treats metallurgy as a whole and does not, as 

 is so frequently the case, subdivide it into the so- 

 called ferrous and non-ferrous metallurgy. The 

 practice of differentiating the metallurgy of iron and 

 its alloys from that of the other metals has its origin, 

 of course, in the outstanding practical importance of 

 these materials and the scale on which the}' are manu- 

 factured, but there is no scientific reason for making 

 any distinction of this kind, and indeed, there is little 

 doubt that if there were more interchange of opinion 

 between those engaged in the various metal industries 

 it would be of considerable benefit to all concerned. 



The first ten chapters deal with general metallurgy 

 under the headings (1) ores and metals, (2) fuels, (3) 

 refractories, (4) the preparation of ores, (5) crushing, 

 grinding, screening, and classifying, (6) metallurgical 

 furnaces. (7) combustion, (8) metallurgical thermo- 

 chemistry, (9) roasting, and (10) concentration of ores. 

 Inasmuch as these aspects of metallurgy are com- 

 pressed into 117 pages, the treatment is necessarily 

 somewhat brief. The author, however, has economised 

 space in not attempting to describe methods not now 

 in use. Compactly as the subjects are dealt with, it 

 would appear' that terseness has been carried to an 

 extreme in attempting to describe the concentration 

 of ores by gravity, by concentrating tables, and by 

 oil flotation in three pages, a considerable part of 

 which is occupied with diagrams. 



The remainder of the book treats of the metallurgy 

 of gold, silver, iron, copper, lead, and zinc in so far as 

 extraction and refining processes are concerned. Xo 

 attempt, however, is made to deal with the mechanical 

 treatment of metals, either in the hot or cold state, 

 nor their working up into finished products. One of 

 the characteristic features of American metallurgy is 

 its emphasis on the efficient mechanical handling of 

 the materials used in producing the metals and it is 

 natural, therefore, to find this aspect of the subject 

 well treated. The author's account of the metallurgy 

 of gold, silver, copper, and lead is, on the whole, sati 

 factorv. The metal iron, however, receives something 

 less than its share of credit, for an attempt is made 

 to describe the production of wrought iron in les than 

 three pages. To try to deal with the manufacture 

 ol wrought iron without any account of the mechanical 

 treatment necessary, except in the most perfunctory 

 fashion, is certainly unusual. With regard to zinc, 

 it is somewhat curious that, considering the importance 

 of the present-day production of electrolytic zinc, very 

 little more than one page is devoted to it. 



The last two chapters give a brief account of plant 

 and equipment and their cost and the business of 



