888 Structural Theory of the Chemical Elements. 



These form a very definite system, with the pecularity 

 that the usual groupings are replaced to a great extent by 

 helium groups. When the suggested constitution of argon, 

 5He 2 , is considered, it is seen that they do not violate the 

 usual relation to the inert gases. 



Perhaps this preponderance of helium, that is to say, ol 

 the positive charges of only two types which may be the 

 nuclei of the helium atom, may be responsible for the peculiar 

 properties and isolated position oE these elements. It is 

 especially noteworthy that the formula for iron consists only 

 of these. 



Uranium. — Perhaps a suggestion with respect to the re- 

 lation between uranium and actinium may be made at this 

 point, though it is highly speculative. If the present atomic 

 weight of uranium, recently determined carefully, be accepted 

 it is in accordance with the constitution 



Uranium, 8{Nu 2 (PfH) 8 }4{He 2 Nu 2 (PfH) 3 }2{He 2 (PfH) 3 } = 238'50, 



giving this accepted value exactly. This formula is a 

 multiple of 3. Actinium is believed to be a branch product 

 of the activity of uranium, and there is certainly a con- 

 siderable gap between the atomic weights. An instability 

 arising in an atom of uranium may in certain cases cause 

 instability in a neighbouring atom, or the unstable atom may 

 be projected into the. stable one, so that they break up 

 together. If this should happen three atoms or more of a 

 new substance may be formed, presuming that the result is 

 not a mixture of elements. If three atoms were formed the 

 atomic weight of the substance would be f of that of: uranium, 

 or 159'00. Its constitution might be arranged as 



6{Nu 2 (PfH) 3 }4{He 2 (PfH) 3 }Nu 4 , 



derived directly from the formula for uranium. The escape 

 of two a particles of constitution Nu 2 and atomic weight 

 3*25 would then leave the substance already indicated as the 

 probable actinium emanation. If four a particles escaped 

 each might be nebulium. 



It is noteworthy that in the September number of the Philo- 

 sophical Magazine Mr. G. N. Antonoff describes experiments 

 which seem to indicate a branch product UrY derived in small 

 quantity from uranium. This product appears to give off 

 a rays, but not to the extent expected from the ft radiation. 

 If it be the parent of actinium, perhaps these a rays are not 

 from UrY, but from one of its products. 



At this point it is convenient to close the present paper. 

 The views which have been advocated are capable in several 



