A CENTURY OF CHEMISTRY. 109 



confirming the doctrine of the regularity of chemical 

 proportions in all combinations. 



Others again, without accepting any protyle-hy- 

 pothesis, pointed out the existence of serial regular- 

 ities in the atomic weights of the elements, (Lens- 

 sen 1857, Pettenkofer 1850, Dobereiner 1817, and 

 even before the atomic theory, J. B. Richter 1798). 

 Dobereiner pointed out that a number of elements 

 could be arranged in groups of three, or triads; e.g., 

 calcium, strontium, and barium, the members of each 

 triad having analogous properties and displaying a 

 certain regularity in the relations of their atomic 

 weights. This idea of family characteristics was 

 afterwards extended by Dumas. 



Most noteworthy, however, was the work of New- 

 lands (1863-4), who showed that when the elements 

 were arranged according to the magnitude of their 

 atomic weights, " similar elements were found at 

 approximately equal distances in the series; count- 

 ing from any one element, every eighth was in gen- 

 eral more similar to the first than the other ele- 

 ments." ^ 



As the eighth element, starting from a given one 

 is a kind of repetition of the first, like the eighth note 

 of an octave in music, he called the regularity ^^ The 

 Law of Octaves." He did not succeed, however, in 

 fully carrying out his idea. In the same year 

 (1S64), Dr. Odling also published a suggestive pa- 

 per on " The Proportional E'umbers of the Elements 

 and their Serial Relations." 



Independent Discovery hy Meyer and Mendelejeff. 

 — We accept the conclusion of expert authorities 

 that in 1869 Lothar Meyer and D. Mendelejeff inde- 



* Ostwald, General Chemistry, trans, by Walker, 1890, 

 p. 35. 



