20 The Philippine Journal of Science 
CONCLUSION 
Anyone who has found it necessary to use as guides in ex- 
perimental work such valuable but hazy and incomplete valence 
theories as those of Werner, Thiele, Friend, and Nef will wel- 
come Langmuir’s octet theory of valence as the true ‘‘key to the 
situation.” It is hoped that the proposed system of structural 
formulas will be found valuable not only as a method for rep- 
resenting the primary valence relations of atoms in molecules 
but as a better basis than has been available in the past for the 
study of polarity, secondary valence, reactivity, selective absorp- 
tion, and other phenomena depending on the shell electrons. It 
has enabled the writer to see certain perplexing reactions in a 
new light, and has led to the formulation of a theory of reaction 
mechanism of the direct union, which will be published in the 
near future. 
SUMMARY 
1. A system for writing structural formulas has been devised, 
based on the octet theory of valence as presented by Langmuir. 
2. The new feature of the system is a distinction between 
“normal” and “borrowing” unions which enables the actual 
valence relations of the atoms to be represented in the formulas. 
3. The borrowing union, AB, is unique in that it is polar in 
the direction A —*B although the shared pair is held more 
closely by B. 
4. The mode of application of the system to all of the known 
elements has been indicated. 
5. The system in itself represents only the primary valence 
relations of the atoms, but can easily be adapted to the study 
of other phenomena depending on the valence electrons. 
