5 8o 



NA TURE 



[April 19, 1906 



detailed and historical survey of the chemical processes 

 which were employed before the metal was produced 

 upon a commercial scale by the aid of the electric 

 current. The successful chemical processes which 

 were all based upon the reduction of salts of alumin- 

 ium with sodium and were simply modifications of 

 ilii method used by Wohler in 1S2 7, when he discovered 

 the metal, brought first and foremost in their train the 

 remarkable cheapening in the manufacture of sodium ; 

 because unless sodium could be obtained at a low 

 cost it was impossible to manufacture aluminium 

 cheaply. However, by purely chemical processes it 

 was never found possible to produce aluminium 

 below about thirty shillings per kilo. In fact, in 1889 

 the price was 38s. per kilo., but at the end of [891, 

 soon after the advent of successful electrolytic pro- 

 cesses, it had fallen to 5s., and at the present day it 

 is rather less than 25. per kilo. 



Minet describes the electrical and electrolytic 

 methods in chronological order. To the brothers 

 Cowles, ol America, belongs the honour of first pro- 

 ducing a working furnace in which they wen abli 

 to obtain allo)s of aluminium with other metals, by 

 striking an arc in a mixture of bauxite and oxide of 

 iron or other metal. The Heroult seems to have been 

 the first furnace in which a fused aluminium salt- 

 cryolite — was actually electrolysed on a commercial 

 scale, and modifications of this furnace are at the 

 present day among the most successful which are 

 employed, and tin- one worked by the British Alu- 

 minium Co. at Foyers is a Heroult. The production 

 of aluminium is essentially one of electrolysis, but it 

 is also electrothermic in so far as the passage ol the 

 current serves to keep the bath molten. The bath 

 usually consists in the first place of fused cryolite, and 

 as the electrolysis continues the loss of aluminium is 

 replaced by additions of aluminium fluoride or ol alu- 

 mina. If the bath were regenerated by continual 

 additions of cryolite, in time the quantity of sodium 

 fluoride would become excessive, and sodium and not 

 aluminium would be yielded up at the kathode. 



Most authorities consider that in a bath which is 

 regenerated with alumina the alumina and not the 

 fluoride undergoes electrolysis. Minet, however, con- 

 siders that it is the aluminium fluoride which under- 

 goes electrolysis, and that the fluorine given up at 

 Mm .mode continuously reproduces cryolite. 



Pari ii. deals with " aluminium and its alloys." In 

 I his the author deals with the cost of the production of 

 aluminium and its alloys. Aluminium is perhaps of 

 more general use in the form of its alloys than in the 

 pure condition. We see that Minet mentions its use in 

 the pure state for surgical instruments — woe betide 

 these instruments if antisepticised in mercuric chloride. 



A lew very interesting pages are devoted to the em- 

 ployment of aluminium as a reducing agent, in the 

 production in the pure state of such metals as 

 chromium, vanadium, manganese, &c, and also for 

 welding purposes. Minet states that ingots ol 

 chromium weighing mo kilos, are prepared at F.sseii 

 in one charge, and the production of this quantity ol 

 metal is said to take only twenty-five minutes. 



The translator contributes a short appendix upon 

 NO. IQO3, VOL. T^\ 



" Aluminium in the United States." The book may 

 be heartily recommended as a very useful contribution 

 to the subject. F. M. P. 



PETROL MOTOR-CARS. 

 Motor-car Mechanism and Management. In three 

 parts. Part i. The Petrol Car. By W. Poynter 

 Adams. Pp. x+174. (London : C. Griffin and Co., 

 Ltd., 1906.) Price 5s. net. 



THE author states that his object is to put into the 

 hands of owners and drivers of motor-cars in a 

 convenient and handy form some knowledge of the 

 general mechanical principles which ought to be 

 understood by those who drive them. 



This idea has been carried out very fairly. The 

 early chapters on the engine and on the various organs 

 are treated in sufficient detail, and although there are 

 a lew blemishes and mistakes, these are not of any 

 considerable importance. 



When, however, the author deals with a matter 

 which is extremely difficult for the average car-owner 

 or driver to understand — namely, the understanding 

 and care of the electrical accessories, which are now 

 everywhere used — we can have nothing but praise for 

 the very thorough manner in which this very difficult 

 question has been dealt with ; in fact, it is evident 

 that the author is a trained electrical engineer, and 

 has consequently been able to approach this subject 

 from the standpoint of one who has had to explain 

 1 he nature of electrical developments to the ordinary 

 user of electric apparatus. We think the author's 

 short and concise descriptions of the various sources 

 of electrical supply which are now available, his de- 

 finitions of conductors, insulators, and other electrical 

 terms which must be used to make his explanations in- 

 telligible, are so good and so well arranged that they 

 should be read by anyone who wishes to obtain a 

 bird's-eye view of electrical engineering so fai as ii 

 applies lo ordinary users of electric light and powei ; 

 at any rate, it is certain that the average user of the 

 modern motor-car finds himself very frequently at fault 

 when he has to puzzle out stoppages on the road due 

 more to the failure of his electrical accessories than lo 

 any other cause, excepl perhaps that of the universal 

 bugbear, the care of the pneumatic tyres. 



On p. 85, when mentioning the importance of a 

 good compression in order to get economical working 

 ol the engine, the author makes statements which 

 are liable to mislead the user when he says that 37 

 per tent, of the full value of the charge is transformed 

 into useful work, and that if the compression is in- 

 1 leased to ioolb. this may be increased to 45 per cent. 

 We find no note correcting this by explaining how 

 ibis refers to a perfect engine, and that with such 

 forms of internal combustion engines as are used 

 lor iars not more than 50 per cent, of such efficiencies 

 are likely to be realised. 



At the present day, when so much is being said as 

 to the want of courtesy and consideration for other 

 users of the road by the drivers of motor-cars, the 

 author's remarks from p. 15 to the end ought to be 

 read by everyone who drives a car. 



