7 io SCIENCE PROGRESS 



The atomic volume of carbon is less than that of other elements, 

 and accordingly when a metal or metalloid unites directly 

 with carbon there is room for the maximum number of 

 associating units. 



Organic Derivations of Selenium and Tellurium 



Considerable attention is now being given to the study of 

 organic compounds of selenium and tellurium owing to a recent 

 statement made by v. Wassermann to the effect that com- 

 binations containing these elements had been noticed to induce 

 diminution in the growth of malignant tumours. Bearing in 

 mind the beneficial results obtained with atoxyl and salvarsan, 

 it seems likely that the most promising field for research lies 

 in the study of the aromatic derivatives of these two elements. 

 The Grignard reaction is available for both, and recently it 

 has been found that selenium can be introduced into aromatic 

 nuclei through the agency of the diazo-reaction. The following 

 series has been completed by Mr. Elliott of the Royal College 

 of Science, Dublin. Starting with diazotised para-nitraniline, 

 selenium is introduced by the action of potassium selenocyanide 

 KCNSe : 



N0 2 /~ ~\N 2 C1 -> N0 2 ^^>Se.CN -> 



N ° 2 ( )~ Se - Se ~ C ^) NQ 2 -» 



NH 2 /~ ~\— Se . Se— f ~\ NH 2 (VIII.) 



The organic selenocyanide when hydrolysed yields 

 di-^>-nitrophenyldiselenide ; this on reduction furnishes 

 di-/>-aminophenyldiselenide (VI II.), an oxidisable base which, 

 like salvarsan, can be utilised in the form of its more stable 

 dihydrochloride. 1 



1 Alternating in the periodic scheme with the arsenic and selenium families, 

 we find, as in other cases, two other groups of elements showing little or no 

 capacity for yielding organic derivatives ; these are the vanadium family (with 

 columbium and tantalum) and the chromium family (with molybdenum, tungsten, 

 and uranium). It was formerly supposed that tungsten had yielded organic 

 derivatives, but this statement has since been contradicted. 



