1886.] NEW YORK ACADEMY OF SCIENCES. 183 



bility of greater uniformity in the standard of values for the 

 atomic weights. 



Contrasting strongly with belief in the absolute character of 

 the weights of atoms is the suggestion of Boutlerow and others 

 that tiie law of definite proportions is subject to variations. In 

 1880, Schiitzenberger observed a curious anomaly in analyzing 

 some hydrocarbons. lie found that the' sum of the carbon and 

 liydrogen was 101 for 100 i^arts of material, the result under 

 other conditions being normal. Boutlerow called attention to 

 this, and expressed the opinion that the chemical value of a con- 

 stant weight (or rather mass) of an element may vary, and that 

 the so-called atomic weight of an element may be simply the 

 carrier of a certain amount of chemical eneigy which is variable 

 within narrow limits. At a meeting of the Chemical Society of 

 Paris, where Professor Wurtz presented a summary of the views 

 of Boutlerow, an interesting discussion followed; this subse- 

 jquently drew from Prof. Josiah P. Cooke, of Harvard, a commu- 

 nication in which he shows that he had expressed similar views 

 more than twenty-five years before. As early as 1855, he had 

 questioned the absolute character of the law of definite propor- 

 tions, and had suggested that the variability was occasioned by 

 the very weak affinity between elements manifesting a fluctuating 

 composition. These speculations are interesting to theorists, but 

 do not seriously impugn the status of chemical philosophy.' 



(6.) For many years, chemists have dimly perceived the proba- 

 ble correlation of the properties of the elementary bodies and 

 their atomic weights. Dumas pointed this out for certain marked 

 groups, Newlands '" emjihasized it; but it remained for a Eus- 

 sian chemist, Mendelejeff," to establish, in 1869, a law of great 

 importance. Mendelejeff showed that if the elements are grouped 

 in the order of their atomic weights, it will be found that nearly 

 the same properties recur periodically throughout the entire 

 series. This so-called Periodic Law is more concisely stated 

 thus: The jn'operties of the elements are periodic functions of 

 their atomic weights. The accuracy of the deductions based on 

 this law is strikingly shown by the fact that MendelejefF, finding 

 an unfilled blank in the periodic system, boldly announced the 

 the general and special properties of the element awaiting dis- 

 covery; six years later, Lecoqde Boisbaudran discovered gallium, 

 an element which proved to have properties almost identical with 

 those of the hypothetical eka-aluminium described by Mendele- 

 jeff. And in 1879, the accuracy of MendelejefE's prophecy was 

 further confirmed by Nilson's discovery of scandium,'^ the coun- 

 terpart of the hypothetical ehaior. Eka-silicon, though yet to 

 be discovered, may almost be regarded as a known element, 

 so fully have its properties been predicted." 



