78 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Proufs Hypothesis. — This old idea that the atomic weights 

 of the elements heavier than hydrogen are exact multiples of the 

 latter has been elaborately discussed by William D. Harkins 

 and Ernest D. Wilson in two articles entitled, " The changes 

 of mass and weight involved in the formation of complex atoms," 

 and " The structure of complex atoms. The hydrogen-helium 

 system." Taking the first 26 atomic weights above hydrogen in 

 the order of magnitude, it is found on the basis of hydrogen as 

 unity that nearly all of them show negative variations from whole 

 numbers. Thus, the atomic weight of helium is 3 - 97, lithium is 

 6*89, and boron is 10"91, which give the variations — - 03, — 0"1J 

 and —0-09 respectively. When these variations are calculated as 

 percentages, the striking fact is observed that with the exception 

 of Be, Mg, Si and CI, which show positive variations, the average 

 negative variation of 21 atomic weights is - 77 per cent, while 

 the six elements from boron to sodium show values of - 77, 0*77, 

 0-70, 0-77, 0-77 and 0*77 per cent. The values of P, V, and Cr 

 are 0*71, 0-77 and 0-77 per cent, while the others vary between 

 - 40 per cent for Al and 1*06 per cent for Fe. The negative devia- 

 tion is, therefore, not a periodic bnt a constant one. The authors 

 call this negative variation a packing effect, meaning that when 

 several hydrogens are united to form a heavier atom there is a 

 loss in weight amounting to about 0*77 per cent of the whole. 

 When oxygen as 16 is taken as a basis for the atomic weights of 

 the 21 elements under consideration their variations from whole 

 numbers are very slight, as is well known. The " packing effect " 

 occurs in the oxygen as well as in the others, so that in this case 

 it is eliminated, and Prout's hypothesis in this modified form 

 applies to these atomic weights. The deviation from whole num- 

 bers averages only - 05 unit for the 21 elements, and the proba- 

 bility that such values should occur by accident is so slight as to 

 be unworthy of consideration. 



There are many points discussed by the authors in their inter- 

 esting articles that will not be mentioned here, as it is intended to 

 present only such features of the discussion as have a very direct 

 bearing on Prout's hypothesis. No explanation is advanced in 

 regard to the atomic weights of the elements magnesium, silicon 

 and chlorine, which are exceptional among the lighter atomic 

 weights in not approaching close to whole numbers, and in show- 

 ing positive variations when hydrogen is used as unity. Further 

 than this, the authors have found that the lemaining 42 elements 

 with heavier atomic weights, from nickel upward, show no tend- 

 ency to approximate to whole numbers, since the average of their 

 deviations is very close to - 25 unit, which would be expected 



