JOURNAL ^"..^ ..tu« 







Elisha Mitchell Scientific Society 



Volume XXXVII MARCH Nos. 3 and 4 



ISOTOPES 

 By Francis P. Venable 



The fundamental conception in chemistry is that of the atom. The 

 atomic theory is the basis of all explanations offered as to the consti- 

 tution of matter and such reactions and other chans'es as may occur 

 in matter. The atom is possessed of certain characteristics or proper- 

 ties that distinguish it. It has even been sugo'ested that an atom is 

 a bundle of properties. The mass or weio-ht of the atom has been as- 

 sumed to be an unvarying;- property and hence to be classed as a con- 

 stant of nature. 



The determination of one of these constants, which after all means 

 an attempt at measurino' the attraction exerted by other masses of 

 matter upon it, is of course relative in its results and beset by many 

 difficulties and chances for error. At first the methods used were too 

 crude and the results obtained too inaccurate to .iustifj^ any conclu- 

 sions as to the unvarying nature of these so-called constants, but with 

 the improvements in apparatus, methods, and manipulation there was 

 reached a degree of confidence which caused some investigators to 

 question the constancj^ of the atomic weights. Schiitzenberger, Bout- 

 lerow, and others raised this question but no satisfactory conclusion 

 could be reached so long as the possibility of error in such determi- 

 nations was unavoidable. There was, however, a persistent suspicion 

 that changes in the atomic weights might occur in the course of chemi- 

 cal reactions. To refute this we have the well-known experiment of 

 Landolt which proved that within the limits of experimental accuracy 

 no change in the sum of the total interacting weights of matter can 

 be detected when chemical action takes place. For the usual routine 

 work of the chemist, then, it can be taken for granted that the weight 



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