PRESIDENTIAL ADDRESS SECTION B. 61 



there is scarcely any free hydrion, the constitution being not unlike 

 that of C 2 II 6 . No doubt aqueous hydrochloric acid when strong 

 contains (OH 3 ) CI and (OH 4 ) Cl 2 . On this theory the angle 

 between the two valencies of oxygen is not very different from that 

 in the case of carbon. Hence H — O — H is misleading, and H,0' 

 should be printed ^ H 



\H 



Another spatial consideration is that NH 4 ion, owing to fhe' 

 fact that the tetrahedron of hydrogen attached to valency 

 electrons is far out from the N atom, has an abnormally large 

 volume (as compared with sodium). This agrees with the fact that 

 ammonium and the large atom rubidium (weight 85) are mutually 

 replaceable in crystals. 



The conceptions for KN0 3 and KC10 4 are specially interesting. 

 The N0 3 ion has 23 plus charges (3 sixes from oxygen and one 5 

 from nitrogen) and 24 binding electrons (3 octets) : its valency is 

 therefore --1, the same as that of fluoride ion (valency +7 — 8). 

 Similarly the CIO, ion has 7 + (4x6)- 31 plus charges, and 32 

 binding electrons (4 octets), giving a total valency of — 1 also r 

 similarly SO, has 30 plus and 32 minus, giving a valency of —2:. 

 PO, similarly is 29 plus and 32 minus = —3. 



This paper would not be complete without some account of the 

 nature of the spectrum lines of the elements. In the first place it 

 is known that these lines, like the valency of the element, have 

 their origin in the outermost electron-shell of the atom. The 

 spectrum of hydrogen which by theory arises from a single 

 electron* has been already reduced to a mathematical formula, viz., 



-r- = 1097 I ^5 ™ I in which N is successively 3, 4, 5, 6, etc. 



This is a harmonic series beginning with A 6563 (line C of the sun) 

 and terminating by superposition at A = 3650. Hydrogen has 



also an ultra-violet spectrum for which '/ A = 1097 I 1 — N 2 J and 



N is 2, 3, 4, etc., successively. Similar but more complex, 

 formulae, also depending on inverse squares of natural numbers, 

 hold for the other elements. 



N. Bohr has suggested that the cause is revolution of the 

 electron in a constant slightly-elliptic orbit round the nucleus, with 

 the possibility of it suddenly jumping from one orbit to another, 

 thus giving what is called a quantum of radiation. The mathe- 

 matics of this peculiar theory lead not only to the above formula 

 for the frequency of the different kinds of light emitted, but also' 

 predict the fine structure of the spectrum lines when seen under 

 high resolution. Nevertheless Sir J. J. Thomson declares that 

 when there are several electrons no stable orbit is possible, so he 

 suggests that the electrons vibrate in and out instead of round, that 

 the nucleus repels when the electron goes near and attracts when 

 it is far, thus giving a neutral position where there is no force, 

 which neutral position is that of the electron in the unstimulated 

 atom. This theory also leads to the octet (skew-cube) arrangement" 

 when the number of electrons is large. Now in crystals it is known 



