April i8, 1901] 



NA TURE 



58; 



case, viz. that of the electrolysis of fused sodium chloride, 

 Mr. Blount says : 



" Thus in practice he who is firmly grounded in these 

 primary principles can deal with each particular case as 

 it arises, not experimenting blindly, but with certain 

 definite and exact generalisations to guide him." 



This is very true, but the example taken is one in 

 which the course of reaction is very readily followed out, 

 and although we presume Mr. Blount does not profess 

 to deal exhaustively with this phase of the subject, yet 

 the section would have been much more instructive if 

 Mr. Blount had also included an example where the main 

 reactions are masked by secondary changes. 



The next section deals with " Winning and refining of 

 metals by electrolytic means in aqueous solutions." To 

 the winning and refining of copper as being "the largest 

 of all electrolytic industries " is assigned the chief place. 

 The author has failed to treat this part of the subject 

 with sufficient breadth. There are two main methods for 

 obtaining copper electrolytically — the multiple system, 

 in which the anodes and kathodes are suspended oppo- 

 site to each other, and the series or Hayden system, in 

 which at one end of the vat there is an anode plate, at 

 the other end a kathode plate, the intervening space 

 being occupied with plates of the same quality as the 

 anode plate. These plates function both as anode and 

 kathode, the surface opposite the anode acting as kathode, 

 that opposite the kathode as anode. Mr. Blount has 

 dealt fairly fully with the multiple system, but only very 

 shortly with the Hayden system, which he condemns, 

 hardly, however, giving sufficient evidence for his con- 

 demnation. Surely, also, a little more space might pro- 

 fitably have been devoted to the treatment of the anode 

 sludge, the successful working up of which often goes 

 a long way towards making an electrolytic process a 

 paying one. 



On p. 125, with reference to the difficulties met with 

 in obtaining nickel in a state of purity, the author gives 

 this useful warning : 



"The study of the degree of purification effected by 

 the electrolytic refining of nickel is particularly instruc- 

 tive, and should suffice to dispose of, once for all, the 

 ridiculous belief that a metal prepared by electrolysis is 

 necessarily and ipso facto of unusual purity." 



The author is hardly correct in saying that no serious 

 attempt appears to have been made to refine tin electro- 

 lytically. He is evidently unaware that a patent has 

 been taken out by Mr. Claus for refining impure tin. 

 In Mr. Claus's process, tin cast into plates is made the 

 anode in a bath of sodium sulphide, the kathode being 

 of tinned iron. The impurities, as well as gold and silver, 

 remain in the anode sludge, and tin is deposited in a very 

 high state of purity at the kathode. 



Probably the third section, which treats of the electro- 

 lysis of fused salts, will be of most interest to the general 

 reader, seeing that under this head the production of 

 aluminium is naturally dealt with. The short section 

 on the electric furnace, carbides and the researches of 

 Moissan, which follows, will repay perusal, if only by 

 pointing out the vast fields of research which the intro- 

 duction of electricity to chemical processes has opened up. 



Section vi., which is assigned to alkali, chlorine and 

 their products, is extremely disappointing. This branch 

 NO. 1642, VOL. 63] 



is, perhaps, one of the most important in the whole range 

 of electro-chemistry, and should therefore have been 

 treated comprehensively. The production of chlorine 

 and caustic soda by electrolysis of common salt receives 

 somewhat exhaustive treatment. But the important, 

 much-worked-at and widely-debated subject of hypo- 

 chlorites and chlorates, together with the practical and 

 theoretical causes which underlie these processes, are 

 handled most inadequately. The casual reader would 

 carry away the impression that if a cold solution of a 

 chloride is electrolysed without a diaphragm, a solution 

 of a hypochlorite will be produced, but that on electro- 

 lysing at high temperatures a chlorate will be obtained. 

 Unfortunately, the electrolysis of a chloride is by no 

 means so simple. There is a very large amount of 

 literature on the subject, and if Mr. Blount had en- 

 deavoured to summarise the various methods and the 

 theories advanced, this section would have been very 

 valuable, but he has unfortunately failed to do this. 



The part devoted to electrolysis of organic compounds 

 is short, and therefore it would be rash to expect too 

 much from it. 



The book as a whole is eminently readable, but it is 

 doubtful whether it will be of much value to the manu- 

 facturer orpractical chemist. But, in fairness to the author, 

 let us not forget that it is extremely difficult to obtain 

 trustworthy and authentic information of manufacturing 

 processes ; the main facts may be published, but it is 

 often the seemingly unimportant details which make or 

 mar a process. The value of the work to the scientific 

 reader would have been greatly enhanced if the author 

 had given references to the original literature from which 

 he obtained his information. To general chemical 

 students the book, although not entirely up to date, may 

 be recommended, in that it deals with the newest of 

 chemical industries in an interesting manner, and will 

 perhaps induce some of the younger chemists to engage 

 in this important branch of study. 



F. MOLLWO Perkin. 



SCLATERS MAMMALS OF SOUTH AFRICA. 

 The Mammals of South Africa. By W. L. Sclater. 

 Vol. ii. Pp. xii-l-241. Illustrated. (London : Porter, 

 1901.) 



THE first volume of this important work having been 

 already reviewed in these columns, and its main 

 scope and style referred to, our notice of the second and 

 concluding volume may be comparatively brief, especially 

 as it is chiefly devoted to the smaller mammals, such as 

 rodents, bats and insectivora, which command a much 

 smaller sphere of general interest than is the case with 

 their larger terrestrial relatives. 



In describing the rodents and bats, the author has 

 been confronted with a task of considerable difficulty on 

 account of having access to the types of many species 

 only during short and busy visits to England. Conse- 

 quently a considerable portion of this section of the 

 work partakes in some degree of the nature of a com- 

 pilation ; and Mr. Sclater himself would probably be 

 among the first to admit that some amount of re- 

 vision will have to take place in the future with regard 



