NATURE 



281 



THURSDAY, JUNE 13, 1918. 



ALUMINIUM AND RARE EARTH 

 METALS. 



A Text-book of Inorganic Chemistry. Edited by 

 Dr. J. Newton Friend. Vol iv., Aluminium 

 and its Congeners, including the Rare Earth | 

 Metals. By H. F. V. Little. Pp. xx + 485. ; 

 (London: Charles Griffin and Co., Ltd., 1917.) 

 Price 155. net. 

 I T^HIS book, the fourth of the series of nine 

 \ -■- volumes which constitute the "Text-book of 

 Inorganic Chemistry," edited by Dr, J. Newton 

 Friend, deals with the members of the third group 

 of the Periodic Table. The arrangement of the : 

 subject-matter of the treatise in accordance with ' 

 Mendeleeff's scheme has, no doubt, much to re- i 

 commend it. The classification, of course, rests ; 

 upon a rational basis, very different in character ' 

 from the arbitrary and often inconsistent methods i 

 which prevailed prior to the enunciation of the 

 epoch-making generalisation of the distinguished 

 Russian chemist. At the same time, it must be 

 admitted that the arrangement brings together 

 elements which, at first sight, seem to have little 

 or nothing in common. We jump, as it were, 

 from boron to aluminium, from aluminium over 

 scandium and gallium to indium, and thence by 

 way c5f the "rare earth " metals to thallium. The 

 older systems at least had the merit of attempting 

 to group the elements so as to bring out their 

 natural affinities as manifested by their chemical 

 and physical attributes, and we seemed to pass 

 from the consideration of one element to that of 

 the next by easy and more or less obvious stages 

 rather than by the brusque and staccato method 

 of violent contrasts which appears to follow from 

 the application of the periodic law. 



Mr. Little, indeed, would appear to have been 

 conscious of the somewhat bizarre effect which a 

 too rigid adherence to the scheme of the table 

 would produce in the arrangement of his material, 

 and* to some extent he meets the difficulty by 

 starting WMth boron as the so-called " typical 

 element," and following on with aluminium as a 

 ■"short period " member. But it is really only in 

 this sense and in its " formal valency resemblance ' ' 

 that boron can be styled a "congener" of 

 aluminium. The other members of the group are 

 *'long period " elements, and are divided into the 

 odd subgroup comprising gallium, indium, and 

 thallium, and the even subgroup which comprises 

 the "rare earth " metals but leads up to actinium, 

 the relations of which to its "congeners" are as 

 yet very ill-defined. Debierne regarded, actinium as 

 allied to thorium, which would place it in the next 

 main group, but such congenital affinities as it pos- 

 sesses point to its being more akin to the cerium 

 I gfroup, and thus afford some slight ground for 

 \. placing it in the position assigned to it by the 

 I author. 



In a short introductory chapter Mr. Little 

 frankly faces the difficulties which his arrangement 



NO. 2537, VOL. lOl] 



involves, and which grow uf)on him when he deals 

 with the "rare earths," and in a few paragraphs 

 refers to the analogies and discordances to which 

 it leads. The student, therefore, is warned,. at the 

 outset, of its limitations — limitations necessarily 

 imposed by the imperfect and provisional nature 

 of the generalisation on which it is based, and of 

 which the weakness is plainly revealed in the case 

 of the "rare earth " elements. 



With regard to the main body of the book we 

 have little but praise. It has evidently been most 

 carefully and conscientiously compiled, and prac- 

 tically every statement has been verified by refer- 

 ence to the original sources of information. The 

 bibhc^raphy, indeed, is one of the most valuable 

 features of the work, and will be appreciated, not 

 only by the student, but also by the investigator, 

 who may have to concern himself with the litera- 

 ture relating to the various elements and their 

 compounds dealt with in the book. 



The chemical history of boron has been brought 

 up to the date of publication, but since the issue 

 of the work much additional information has been 

 gained respecting the many unstable hydrides of 

 boron — a particularly difficult class of substances 

 to deal with, but which have been investigated 

 with great skill by Stock and his collaborators. The 

 industrial extraction of boric acid and the manu- 

 facture of borax scarcely receive the treatment 

 which they deserve as being by far the most im- 

 portant of the boron compounds. Incidentally, the 

 writer terms the jets of steam from the volcanic 

 vents in Tuscany suffioni instead of soffioni. 



A good description of the methods of manu- 

 facture of metallic aluminium is given, together 

 with a short account of its alloys, many of which 

 are of growing importance. Compounds of alu- 

 minium, including some of the more important 

 '■• aluminous minerals, are dealt with in fewer than 

 ^ forty pages. The treatment is necessarily very 

 i slight in many cases, especially when compared 

 ! with that of the chapter on clay and ceramics, 

 j which extends to more than thirty pages. This, 

 i and also the chapter on ultramarine, which 

 seems to have been largely based- on the article 

 on that subject in Thorpe's "Dictionary of Applied 

 ■ Chemistry," are, judged by their length, the most 

 ! important contributions to industrial chemistry in 

 '■ the book, which is otherwise not remarkable for 

 its technology. 



The most valuable feature of the work is, how- 

 ever, its treatment of the chemistry of the "rare 

 earths." This section occupies more than half 

 the volume, and is without doubt the fullest and 

 most comprehensive account of their history, 

 modes of extraction, properties, and relations 

 , which has yet appeared. 



Although the first "rare earth" was discovered 

 by the Finnish chemist, Gadolin, so far back as 

 1794, and was quickly followed by the isolation of 

 other members of the group by Ekeberg, Berzelius, 

 Gahn, Mosander, Cleve, Hoglund, and others 

 during the next fifty or sixty years, it is only 

 within comparatively recent time that the chemistry 

 of these substances has received its main develop- 



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