256 
CHEMISTRY: I. LANGMUIR 
valence which explains and coordinates the separate valence theories that we 
have needed in the past. 
There are many facts not previously well understood which are very readily 
explained by the new theory. For example, the fact that we have weak and 
strong acids, weak and strong bases, but no 'weak' and 'strong' salts, is auto- 
matically explained. 
The theory indicates that all salts consist of negative and positive ions even 
when in the solid condition, and that no pair of electrons are held in common 
between the negative and positive groups. Thus in sodium chloride the co- 
valence of both sodium and chlorine is zero, and this fact explains the non- 
existence of molecules of sodium chloride shown by the X-ray crystal analysis. 
When sodium chloride is dissolved in water the water does not cause ionization, 
but simply causes the separation of atoms already ionized. This direct result 
of the Octet Theory is in full accord with experiment and with Milner's recent 
theory of strong electrolytes. London, Phil. Mag., 35,' 1918, (214, 354). 
In the field of organic compounds the theory fits the facts particularly well. 
Although in the case of compounds like SFe, H2SiF6, etc., there is very definite 
evidence that the kernels of the atoms of sulphur and silicon are cubical in 
shape, there is the strongest evidence that in organic compounds the carbon 
atom has the eight electrons of its octet drawn together into four pairs, ar- 
ranged at the corners of a tetrahedron. This is in full accord with the fact 
that in SFe, and H2SiF6, the central atom has given up electrons to the sur- 
rounding atoms, so that the cubical kernels do not share any electrons with the 
other atoms, while in organic compounds the carbon atoms always share four 
pairs of electrons with adjacent atoms. From this we must conclude that a 
pair of electrons held in common by two octets acts as if it were located at a 
point between the two atoms. This conclusion, which can be reduced from 
the properties of a very few simple organic compounds is found to apply appar- 
ently without exception to compounds of nitrogen, sulphur, phosphorus, and 
even cobalt compounds, etc. It seems to explain all the cases of stereoisomer- 
ism that I am famihar with. For example, in the amine oxides, NR1R2R3O, 
nitrogen is quadricovalent, so that these substances exist as optical isomers, 
just as in the case of a carbon atom attached to form different groups. 
The isomerism of compounds of tervalent nitrogen such as ketoximes, hy- 
drazones, ozazones, and diazo-compounds, etc., is readily accounted for, as 
well as the absence of isomers among tertrary amines, etc. Not only are the 
substituted ammonium compounds fully explained, but also the sulfonium, 
phosphonium, and oxonium compounds. Thus the structures of S(CH3)30H, 
S(CH3)4Cl2, (C2H5)20.HC1, etc., are readily found from the Octet Theory and 
their salt-like character is explained. The covalence of the central atom in the 
above compounds is three, four and three respectively. 
When the values of e and n are both the same for two or more compounds it 
is evident according to the Octet Theory that these may have practically iden- 
tical structures. An example of this kind is found in N2 and CO. The total 
