CHEMISTRY. 



137 



Charities,'' and Boston, besides issuing valuable 

 tracts, publishes a " Select List " of books and 

 ]>apers on charitable work, to be found in the 

 Boston Public Library and elsewhere. All the 

 larger towns publish annual reports. The 

 American Social Science Association Report, 

 No. 12, contains valuable monographs on 

 charity organization, and there are very many 

 scattered through various State reports, which 

 are lost, except to limited circles. The valuable 

 pamphlet, ' Notes on the Literature of Chari- 

 ties," by Prof. Herbert Adams, issued by Johns 

 Hopkins University, is the best guide to the 

 study of this subject. 



CHEMISTRY, iliemieal Philosophy Pursuing 

 his researches into the nature and origin of the 

 element?, Mr. William Crookes applies the 

 term meta-elements to designate such sub- 

 stances as have been revealed in his own ex- 

 periments and those of Kruss and Nilson in 

 the rare earths, the chemical differences be- 

 tween which are so faint as to render it doubt- 

 ful whether they are to be classed as separate 

 elements or modified forms of the same ele- 

 ment. Among such bodies are those into 

 which yttrium, erbium, samarium, etc., prob- 

 ably split up. When the only perceptible 

 chemical difference is. say, an almost imper- 

 ceptible tendency for the one body to precipi- 

 tate before the other, or when the chemical 

 differences reach the vanishing-point while 

 well-marked physical differences still remain, 

 the problem is an embarrassing one. Seven 

 classes of such rases that have occurred in 

 the author's experiments are described. It' we 

 multiply the elements in accordance with these 

 shades of differences we are liable to come in 

 conflict wit!) the periodic theory, which "has 

 received such abundant verification that we 

 can not lightly accept any interpretation of 

 phenomena which fails to be in accordance 

 with it." To meet this difficulty he applies the 

 hypothesis already suggested in his British 

 Association address on the "Genesis of the 

 Elements" (see ''Annual Cyclopaedia" for 

 1886), that the atoms are not necessarily all 

 absolutely alike among themselves; but that 

 the smallest ponderable quantity of any ele- 

 ment "is an assemblage of ultimate atoms 

 almost infinitely more like each other than they 

 are like the atoms of any other approximating 

 element " ; and that the atomic weight ascribed 

 to the substance " merely represents a mean 

 value around which the actual weights of the 

 individual atoms of the element range within 

 certain limits." 



A theory of the form and action of the atoms 

 of carbon, suggested to Professors Victor Meyer 

 and Riecke by experiments in diversion of the 

 four valencies from their positions, supposes 

 that the atom is a sphere surrounded by an 

 ether-shell, and that it is itself the carrier of 

 the specific affinity, while the surface of the 

 ethereal envelope is the seat of the valencies. 

 Each valency is conditioned by the existence of 

 two opposite electrified poles, forming a system 



called a di-pole. The middle point of the line 

 joining each pair of poles remaining always in 

 the surface of the envelope, but freely movable 

 in it, the di-pole would be able to rotate freely 

 around this central point. The atom being 

 supposed to possess a greater attraction for the 

 positive than for the negative ends of the di- 

 poles, the positive ends would turn toward its 

 center, while the valencies of the same atom 

 would repel each other, and take up their po-i- 

 tions at the corners of the tetrahedron, from 

 which, however, they can be deflected. 



The theory of valency as upheld by Helm- 

 holtz, with its classification of the elements as 

 monads, dyads, triads, etc., according to the 

 number of definite, or atomic charges of elec- 

 tricity which are associated with them, is called 

 in question by Prof. Henry Armstrong, who 

 advances in its place what he terms a theory 

 of "residual affinity." He would define a 

 molecular compound as one formed by the 

 coalescence of two or more molecules, un- 

 attended by redistribution of the constituent 

 radicles, and in which the integrant molecules 

 are united by residual affinities. In other 

 words, the unit charge must be capable in cer- 

 tain cases of promoting the association, not 

 merely of two, but of at least three atoms. 

 After explaining his theory in some of its 

 details, with graphic illustrations, the author 

 adds that if his contention is correct that 

 residual affinity plays a far more important 

 part than has hitherto been supposed, and that 

 it must be taken into account in all discussions 

 on valency, "it follows of necessity that our 

 views regarding the constitution of the majority 

 of compounds at present rest upon a most uncer- 

 tain basis. . . . The properties of compounds 

 being demonstrably dependent on the intra- 

 molecular conditions, it is difficult for a chemist 

 to resist the feeling that the peculiarities mani- 

 fested by the different elements are also very 

 probably the outcome of differences in structure. 

 . . . There appears to be an increasing weight 

 of evidence to favor the assumption that the 

 influence exercised by compounds in cases of 

 chemical change is local in its origin ; that it 

 is exercised more by a particular constituent 

 or constituents in particular directions, in 

 fact than by the molecule as a whole." 



A relation has been discovered by Dr. C. 

 Bender to exist between certain physical con- 

 st'ants and chemical valency. On mixing two 

 chemically inactive salt solutions, the density, 

 expansion, and electrical resistance of the mixt- 

 ure generally diverge very considerably from 

 the arithmetical mean of those of the con- 

 stituents. But Dr. Bender finds it possible to 

 prepare "corresponding" solutions, which, on 

 mixing, shall not exhibit such divergence, and 

 further, the strengths of those " correspond- 

 ing" solutions expressed in gramme-molecules 

 per litre bear extremely simple relations to each 

 other. For example, with respect to density 

 and expansion, a solution of sodium chloride 

 containing one gramme-molecule per litre of 



