292 SCIENCE PROGRESS 



menon Strutt suggests that the character of the impact of the 

 foreign gas with the nitrogen molecules is altered by their 

 known capacity of combining with the free electrons in the 

 discharge space. Argon, helium, and nitrogen itself lack this 

 property, so that, consequently, they are unlikely to function 

 as activators. Mercury vapour, although it promotes activa- 

 tion of the nitrogen, does not, however, assume a negative 

 charge in the canal rays. This anomalous behaviour of mer- 

 cury vapour may possibly be explained when it is remembered 

 that the positive charges borne by the mercury atoms in the 

 canal rays are considerably larger than is normally the case. 

 In connection with these results it is of some interest to find 

 that recently in several papers Baly has put forward a theory 

 of reactivity, based on the opening up of the condensed electro- 

 magnetic force fields of atoms and molecules, by the presence 

 of small amounts of chemically opposite activators. In our 

 present state of knowledge of the exact significance of such 

 intra-atomic and inter-molecular forces it is not impossible 

 that both views have an entirely compatible basis. 



Compounds. — The extended investigations of Stock and 

 Priess on compounds of boron, more particularly the hydrides, 

 have now reached the concluding stages. The chemical be- 

 haviour and physical constants of the trichloride and tribromide 

 class these compounds as distinctively non-metallic. The 

 four well-defined hydrides, B 2 H 6 , B 4 H 10 , B 6 Hi 2 , and Bi Hh, 

 which so far have been isolated, are in the latest paper (Ber, 47, 

 31 15, 19 1 4) studied in respect to their behaviour with chlorine 

 and bromine. Replacement of hydrogen by halogen is the 

 general rule, such compounds as Bi H 12 Br 2 and B 2 H 5 Br being 

 obtained. With excess of halogen B 2 H 6 first gives highly 

 halogenated derivatives like B 2 H 3 X 3 . which later split up into 

 the mono-haloid B 2 H 5 X or the original hydride B 2 H 6 and BX 3 . 

 In no case could evidence of BH 3 or its halogen derivatives 

 be obtained, and such a compound would appear to be as 

 incapable of separate existence as the methyl group CH 3 . 

 The conclusions which the authors draw from their extensive 

 study of these boron derivatives are highly interesting, and 

 mark an advance on previous conceptions. Boron would 

 seem to be an exception to the Bodlander-Abegg rule that the 

 sum of the positive and negative valencies of an element is 

 eight ; its highest negative valency (hydrogen) must be placed 



