492 



NA TORE 



[September 23, 1897 



been visited by the author, and views of many of them 

 are given. We must note one drawback which the 

 volume has, in common with most French books, 

 namely, the absence of an index. F. P. W. 



ELECTRO-METALL URG V. 

 Electric Smelting and Refining: the Extraction and 

 Treatment of Metals by means of the Electric Current- 

 Being the second edition of Elektro-Metallurgie, by 

 Dr. W. Borchers. Translated, with additions, by 

 Walter G. McMillan. Pp. xx + 416. With numerous 

 illustrations. (London : C. Griffin and Co., Ltd., 1897.) 



THOUGH electro-metallurgy may still be regarded 

 as in its infancy, it is such a lusty youngster and 

 is making such rapid progress that it is high time that a 

 good manual on the subject in the English language 

 should be available to our engineers. No better work is 

 \vanted than a translation of Dr. Borchers' well-known 

 treatise, and it has been excellently put into English by 

 Mr. McMillan, who has also done his best to bring the 

 work up to date, a task rendered all the easier by reason 

 of the shortness of the time (considerably less than two 

 years) that has elapsed since the publication of the 

 German edition. The additional matter mainly con- 

 cerns the practical aspect of the subject, accounts of 

 actual applications of processes to which little or no 

 reference is made in the German text being inserted 

 under many of the subheads. With these additions, 

 enough is stated to give a good general idea of the 

 present industrial position of electro-metallurgy. 



Little space is devoted to introductory matter, the author 

 plunging into the thick of his subject almost at once. 

 A short account, however, is given of the newer electro- 

 chemical theories, but the student is referred for fuller 

 explanations to the works of Ostwald and Nernst. 



In Part i., which deals with the alkali and alkaline 

 earth metals, the most interesting section is that on the 

 carbides of calcium, strontium, and barium. The history 

 of the subject is noticeable, as it differs somewhat from 

 that given by M. Moissan in the Annales de Chimie et 

 de Physique last year. Thus Dr. Borchere claims to 

 have produced the carbide of calcium in his electric 

 furnace as long ago as the year 1880, although no use 

 was made of the discovery, which was not published 

 until 1891, until "the later researches of Maquenne, 

 Travers, . and Moissan first recalled attention to this 

 class of compounds " in 1892-94. It is remarkable that 

 Moissan, writing at a later date than Borchers, does not 

 refer to the experiments of the latter. The electric 

 furnace used by Borchers differs from that employed by 

 other experimenters in having a thin carbon pencil 

 connecting two thick carbon cylinders. When the cur- 

 rent is passed, the carbon pencil becomes intensely 

 heated owing to the great resistance offered by it, and 

 the charge, which is packed round it, is heated by con- 

 tact. There is here no possibility of electrolytic action, 

 and it is on the results obtained by the use of this 

 furnace that the author, in 1891, based the law, which 

 he claims to have established, that " all oxides are capable 

 of being reduced by carbon if the temperature is suffi- 

 ciently high" — a law which has not as yet obtained full 

 recognition. 



NO. 1456, VOL. 56] 



The most important parts of the book are, however, 

 those dealing with aluminium and copper. In both these 

 sections the historical accounts are particularly good, the 

 progress of events in the electrolysis of fused compounds 

 of aluminium, for example, being traced from the experi- 

 ments of Davy in 1807 to the practical installation of the 

 Hall process at Pittsburg, working details of which were 

 not published until 1896. Many patent specifications are 

 given and processes mentioned, some of them being ad- 

 mittedly impracticable, and even, in the author's opinion, 

 absurd, for " we may learn something even from negative 

 results." The good points in each and the causes of 

 failure are carefully pointed out, with the result that the 

 history is made most instructive. It is true that Dr. 

 Borchers shows a pardonable tendency to praise what is 

 German and to criticise and decry the work in the United 

 States and elsewhere ; but the translator has in part cor- 

 rected the impression conveyed by this patriotic prejudice 

 by the additions made in many parts of the book. It is 

 disappointing that details are not forthcoming of the 

 work of the British Aluminium Company, which we learn 

 is now the largest producer of that metal in the world, 

 using 2500 h.-p. at their Falls of Foyers works in Scot- 

 land ; but it is, of course, not surprising that manufac- 

 turers, after spending thousands of pounds and much 

 time over their experiments, should prefer to keep the 

 results to themselves for a time. 



The electrolytic refining of fairly pure metallic copper, 

 like the direct reduction of aluminium from its oxide, is 

 of special interest, because all the main difficulties have 

 now been overcome, and a complete account can be 

 furnished. Here again there is a slight tendency on the 

 part of the author to regard the latest German process, 

 the Siemens-Borchers system, as perfection, and to 

 ignore the later American practice, in which a much 

 higher current density is used, and the cost thus 

 materially reduced, in spite of the fact that wages are 

 higher than in Germany. Several exact descriptions of 

 processes in works ai-e given, however, illustrated by 

 capital diagrams, and the whole section is of great value. 

 Passing to other metals, silver, gold, lead, tin, zinc, 

 and antimony all receive adequate treatment, and an 

 interesting description is given of the various processes 

 of electric welding, local softening, and soldering of iron 

 and steel. 



Among minor errors that were noticed may be men- 

 tioned the statement on p. 239, that ores of silver and 

 gold are never smelted with copper ores with the design 

 of concentrating the precious metal in the copper. This 

 method, however, has been in use for some time in New 

 Mexico. Again, the melting-point of gold is given as- 

 1035", a figure long since abandoned, and some erroneous 

 figures are given concerning the relative cost of the 

 Siemens-Halske and other cyanide processes for the 

 treatment of gold ores. Such trivial mistakes do not 

 impair the value of the work, which must of necessity 

 be acquired by every one interested in the subject who- 

 does not already possess the second German edition. 



There is much material for reflection for engineers in 

 England in the phenomenal rapidity with which the 

 practical applications of electro-metallurgy are advancing 

 in Germany and in America. The consideration, in par- 

 ticular, repeated in this volume over and over again, to 



