704 SCIENCE PROGRESS 



(colourless needles), a basic substance insoluble in water, but 

 soluble in nitric acid to the corresponding nitrate, (CH 3 ) 3 Pt . N0 3 . 

 The original iodide combines additively with two molecules 

 of ammonia, a combination which in all probability involves 

 the formation of a molecule having octahedral symmetry: 



NH 3 

 CH 3X /CH 3 2NH3 CH 3 j CH 3 



CH ; 



/' Ni 



CH, j 



NH ; 



At present very little is known regarding the organic 

 derivatives of the other metals of the platinum family. Both in 

 this series and in the first vertical series, including the alkali 

 and currency metals, it is significant that it is the metal of 

 highest atomic weight — platinum in one case, gold in the other — 

 which has combined most readily with alkyl radicals. 



Generalisations 



1. Influence of Atomic Weight on the Stability and Ease 

 of Formation of Organic Derivatives 



In the natural families of elements thus far considered the 

 capacity for forming organic derivatives appears to increase 

 with the rise in atomic weight. Gold and platinum, the final 

 members of their respective groups, have just been cited as a 

 case in point. Thallium, the final member of the aluminium 

 family, is the only one yielding readily both alkyl and aryl 

 derivatives. Iodine, although a non-metal, may be quoted, as 

 it furnishes iodinium bases such as I(C 6 H 5 ) 2 . OH containing two 

 phenyl or other aryl groups, a property which is not possessed 

 by the halogens of lower atomic weight. 



Organo-Mercuric Compounds 



Mercury, the final member of the glucinum family, affords a 

 striking illustration of the great capacity for combining with 

 organic groups possessed by metals and metalloids of high 

 atomic weight. This metal possesses a very marked affinity 

 for carbon, and enters into combination with a large number of 

 organic substances of very varied type. 



In many instances the attachment of mercury to carbon can 

 be effected merely by boiling the organic substance with 

 mercuric acetate in a suitable solvent. This is notably the 



