RECENT PROGRESS IN CHEMISTRY, 527 



ing this subject, at the Aberdeen meeting of the British Association, 

 proposed a " reasonable explanation " of the periodic law ; he regards 

 the elements as compounds of carbon and aether, analogous to the hy- 

 drocarbon radicals, and suggests that all known bodies are made up of 

 three primary elements carbon, hydrogen, and aether an assumption 

 which can not be disproved. In recent years the periodic system has 

 exerted noteworthy influence on the classification of the elements and 

 their compounds. It is of positive utility in determining unsettled 

 questions concerning new and rare elements, and is destined to main- 

 tain a lasting hold on chemical philosophy. 



The question whether the known elements are truly primary forms 

 of matter has long occupied the thoughts of chemists, and the prob- 

 lem constantly acquires new features. The influence of high tempera- 

 tures on the spectra of the metals has been a fruitful source of spec- 

 ulations. In 1878 the English astronomer and physicist Lockyer 

 announced the discovery of the resolution of the elements into one 

 primary matter ; but when Lockyer's paper was read before the Royal 

 Society his discovery proved to be little more than a hypothesis, and 

 that not a new one, he having been virtually anticipated by Professor 

 F. W. Clarke, of Washington. However, Lockyer's hypothesis was 

 based in part upon experimental evidence. After eliminating coinci- 

 dences in the lines of the spectra of various metals, due to impurities ) 

 so large a number of identical lines remained that he advocated the 

 assumption that these are produced by a primary matter common to 

 the so-called elements. He pointed out that in the hottest stars, Sirius 

 for example, hydrogen only is present, and argued that at extremely 

 high temperatures the so-called elements are broken up into hydrogen, 

 the ultimate matter of the universe. Lockyer's announcement excited, 

 temporarily, a lively interest, but his views are not regarded as sup- 

 ported by sufficient evidence. 



More recently, the doctrine of " structure " has been borrowed 

 from organic chemistry, and applied to the elementary bodies ; the 

 relations existing between the elements is so similar in many respects 

 to the relations between the hydrocarbons in a homologous series that 

 the elements have been regarded as compounds of carbon with an un- 

 known primary form of matter. Experimental evidence is lacking, 

 but the hypothesis takes a plausible form. 



During the past year an Austrian chemist has announced the de- 

 composition of didymium by purely chemical means, and the discovery 

 of praseodymium and neodymium as its constituent elements. An Eng- 

 lish chemist claims to have evidence of the existence of an allotropic 

 form of nitrogen. Both these statements await confirmation. 



The views of chemists concerning the nature of affinity and chemi- 

 cal action are undergoing modifications destined to wield an important 

 influence on the science in the near future. The notion has prevailed, 

 though not distinctly formulated, that the chemical attraction exerted 



