480 TRANSACTIONS OF SECTION B. 
Discussion on Valency. 
(i) The Nature of Valency. By Professor W. J. Pops, F.R.S. 
(ii) Zur Valenzfrage. By Professor A. WERNER. 
(iii) Valency. By Professor R. ABEGG. 
The polarity of valency is distributed through the periodic system according 
to a well-defined law ; the valency is strongest on the left, and least on the right 
side, increasing with the atomic weight in the principal groups, decreasing in 
the sub-groups on the left side of the system, while on the right-hand side they 
both increase in the same order as the atomic weights. Decreasing + polarity and 
increasing — polarity are consequently identical. 
The valency number is very simple and constant in compounds with atoms of 
different polarity (heteropolar compounds), while most variable in compounds of 
nearly equal polarities (homeopolar compounds). All elements are able to act 
amphoterically, being positive against stronger negative atoms, and negative 
against stronger positive ones, as is proved either by electrolysis or hydrolysis of 
their compounds. 
The maximum valency number is limited for both + and — valency, the 
former being the number of the group, the latter the number which makes this 8. 
The strength of valency affinity decreases with increasing number of valencies ; 
thus the polarity with the smaller number of valencies becomes prominent and 
forms the ‘normal valency,’ while the other forms the ‘ contravalency,’ thereby 
giving rise to the following table :— 
Number of Group of Period. System| I. Il. / III. | IV. | MOREE MALE VII. | VIII.=0 
Normal valency . ' : +1] +2 
+3)| | a8 1) 94-0 
Contravalency : : 5 -7 | —6 |-5 
| 2 
—bs| +7) \ 45 +6| +7|+8-8 
The contravalencies of the left-hand groups, being originally an extrapolation 
from the behaviour of the right side, may be found in homeopolar compounds of 
the metals—z.e., the alloys. 
Any binary compound is unsaturated with respect to the two valencies of its 
components, only one kind being satisfied. The other valencies can and do act as 
links between binary compounds, bringing about their molecular compounds. ‘The 
strength of their junction corresponds with the strength of the polarities present, 
being greater in the case of normal-valency linkage and smaller in the case of 
contravalencies. 
This system does not claim to be a complete solution of the problem of 
valency; but as many known facts are in accordance with it, and may be explained 
by its help, it might be taken as some approximation to the truth. 
(iv) Dwisibility of Valency. By Professor Huco KAuFFMANN. 
One of the first consequences of the theory of electrons is the divisibility of 
valency, and chemistry furnishes us with much experimental proof of this sup- 
position. The first investigations of this nature were made by Thiele, who as a 
consequence formulated a theory of partial valency. The divisibility of valency 
is most strikingly shown in compounds containing double bonds, and nearly all 
research up to the present has been developed by the aid of such bodies. The 
author’s investigations deal with colour and fluorescence, and it has heen found 
that in the case of benzene derivatives the colour and fluorescence of the sub- 
stance becomes more marked the greater the amount of partial valency in the 
chromophore attached to the benzene nucleus. 
These facts have peculiar signification in the case of chromophores containing 
