94 



Prof. H. E. Armstrong and Dr. T. M. Lowiy. [Mar. 13, 



and most remarkable feature brought out by this mode of classifying 

 the elements is the existence in various parts of the system of groups 

 or series of related elements from the highest term of which alone 

 " progression " takes place. The existence of such groups in the case 

 of the iron and platinum metals and some of the rare earths, has long 

 been recognised — but not their significance. It is not unlikely that 

 some of the columns will be " cleared " of such groups when atomic 

 weights generally are known with a closer approach to certainty. Of 

 their existence in column 4, there can be no doubt ; but if in column 7 

 rubidium were put at 84, 85 could be transferred to column 8 ; and if 

 lower down in the same column, caesium were put at 131, 132 and 133 

 could be transferred to column 8, or the necessary " correction " might 

 be made perhaps with greater advantage by including in column 4 two 

 terms (81 and 82) in the fifth, and three (128, 129, 130) in the seventh 

 period: column 7 would then be free from "grouped" elements. 

 Such groups, however, are undoubtedly as characteristic of column 

 8 as of column 4 ; whether they are of column 9 is open to question — 

 the cerium group might well follow barium in column 8 ; but wherever 

 they may come, it is clear that the elements of this group are a very 

 numerous body, and that a remarkable expansion may be looked forward 

 to in this part of the table. Column 11 might also, by a similar pro- 

 cess, be cleared of grouped elements. If such a clearance turn out to 

 be possible, grouped elements will be characteristic of only three of 

 the families — those in columns 4, 8 and 12. 



Making allowances in the manner suggested, the " smoothed " scheme 

 is arrived at which is embodied in Table II. 



The possibilities disclosed by a system of classification such as that 

 here suggested are remarkable, but they are on the surface and need 

 not be dwelt upon. Speculation on such a subject will be justified if 

 it but lead to further appreciation of the rhythm which undoubtedly 

 underlies the relationships subsisting among the elements. That work 

 in plenty is left for the chemist to do is certain. 



" Persulphuric Acids." By Henry E. Armstrong, V.P.E.S., and 

 T. Martin Lottry, D.Sc. Eeceived March 13, — Eead March 

 20, 1902. 



Although it was observed by Faraday in 1834 that " if the acid 

 were very strong, a remarkable disappearance of oxygen took place " 

 on electrolysing aqueous solutions of sulphuric acid,* it was not until 

 1878 that its disappearance was at all satisfactorily accounted for by 

 the discovery of persulphuric acid by Berthelot. 



* ' Researches in Electricity,' series vii, § 728. 



