848 



SCIENCE 



[N. S. Vol. XLII. No. 1094 



purity and converted into sodium bromide, 

 the amount of silver necessary to precipi- 

 tate the combined bromine being deter- 

 mined. In this way the relation between 

 the atomic weights of bromine and carbon 

 was determined, and the agreement of the 

 values thus found with the parallel work 

 of others gives very satisfactory evidence 

 of the trustworthiness of all the other 

 atomic weights which have been determined 

 at Harvard in relation to bromine. Next 

 came the study of the atomic weight of 

 sulphur, which was studied in somewhat 

 similar fashion, pure sodium carbonate 

 being converted into pure sodium sulphate, 

 and thus the relation between carbon and 

 sulphur found through those salts. The 

 value of sulphur obtained in this way was 

 somewhat less than that ordinarily accepted, 

 but not more than might reasonably be 

 ascribed to the possible errors of previous 

 work. On the whole, these two investiga- 

 tions, in which the purest sodium carbonate 

 formed the starting point, add distinctly to 

 one's confidence in the present accepted 

 table of atomic weights. Both of these in- 

 vestigations were so extremely delicate and 

 so very dependent upon pure, dust-free air 

 that they could hardly have been executed 

 at all in a less perfect building. 



Next, during 1913-14 the atomic weight 

 of lead from radioactive sources was 

 studied; and we found that this sort of 

 lead has an atomic weight distinctly lower 

 than ordinary lead, although no known im- 

 purity could be found in it, and although 

 its ultra-violet spectrum is identical with 

 that of ordinary lead. This work was soon 

 supported by independent and almost 

 simultaneous but less complete and search- 

 ing investigations published in Austria and 

 France; and later has been reenforced by 

 continued research in both continents. The 

 outcome has unusual interest and signif- 

 icance, because it seems to indicate that 



there may be different kinds of lead having 

 many properties precisely similar, but dif- 

 fering as to their atomic weights. The re- 

 search is being continued at the "Wolcott 

 Gibbs Memorial Laboratory, large amounts 

 of radioactive lead having been obtained 

 from Australia, Colorado and Norway 

 through the kindness of scientific friends. 



Whatever may be the final outcome, one 

 can not help thinking that researches of 

 this kind deal with mysteries which are 

 among the most fundamental of all those 

 presented to the physical chemist, for the 

 nature of the chemical elements underlies 

 all the mechanism upon which life depends. 



The study of compressibility was con- 

 tinued in two directions — on the one hand, 

 the behavior under pressure of similar 

 organic substances, and on the other hand, 

 the compressibility of the elements, being 

 carefully studied with increasing accuracy 

 and effectiveness. This seems rather a 

 strange subject to pursue in a chemical lab- 

 oratory; but its interest is truly chemical, 

 because of its relation to the recent theory 

 of atomic compressibility, which gives a 

 new interpretation of the mechanism of 

 chemical action. There is not time to ex- 

 pound this theory at length here, but those 

 who desire acquaintance with it wiU find a 

 fairly complete resume in the number of 

 the Journal of the American Chemical So- 

 ciety for last December.^ Suffice it to say 

 that many facts may be interpreted to mean 

 that the atoms are not hard, incompressible 

 particles, but rather elastic, compressible, 

 deformable entities, capable of yielding 

 somewhat to every source of pressure which 

 may be applied upon them. Moreover, evi- 

 dence is available showing that both chem- 

 ical affinity and cohesion exert pressure in 

 their action, and hence affect the space 



3 Jour. Am. Chem. Soc, 36, 2417-2439 (1914). 

 Many references to other papers on this topic are 

 given in the accompanying bibliography. 



