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Transactions of the Royal Society of South Africa. 
reaction of the water in which they are examined. As all the absorption- 
bands are double, each substance has six bands in all, and it is the object 
of this paper to calculate all the six bands of each substance. 
This leads to the result that each of the six bands corresponds to a 
different chemical constitution, or at least to a different orbital motion of 
an electron round the molecule. 
As examples, _p-oxyazobenzene has AA 433 and 395 when alkaline, 
AA 490 and 463 when acid, and AA about 340 and 315 when neutral, the 
corresponding figures for butter-yellow being AA 490+460 and 543+508 
and about 405 + 375. Taking the former example, the six chemical consti- 
tutions are respectively : Ph . NH . NOH . C 6 H 4 0', Ph . NOH . NH . C 6 H 4 0', 
Ph . NHC1 : N . C 6 H 4 OH, Ph . N : NHC1 . C 6 H 4 OH, Ph . NH . N : C 6 H 4 : 0, 
Ph . N : N . C 6 H 4 OH. 
Solution of the Problem of the Oxy-compounds. 
Let phenate-ion, C 6 H 5 0' have A 287 in water.* 
Let the a-methylene-interposition-colour-factor, -CH 2 -, be 0-92. 
Let the a-imino- ,, ,, -KH-, be 1-09. 
Let the ^-methylene- ,, ,, ,, . be 1-15. 
Let the /3-imino- ,, ,, . be 1-22. 
Let the a-oxidation-f actor be .... 1-10. 
Let the p- „ „ 1-035. 
Let the a-phenyl-substitution-f actor be 1-135.| 
Let the j8- „ „ „ „ . • . 1-03. 
Then we have all the data for calculating the bands of the oxy-com- 
pounds of azobenzene, azomethine, stilbene, benzaldehyde, benzhydrol, 
benzophenone, diphenylamine, triphenylcarbinol, phenylhydroxylamine, etc. 
The method of calculation is, as before, factorial. All the relative 
factors taken from the formula of the substance are multiplied together, 
the result being the wave-length of the band-centre corresponding to that 
formula. For example, Ph NH NOH C 6 H 4 0' gives :— 
287 (phenate)xl-09 (a-imino) X 1-10 (a-oxidation) X 1-22 (ji-imino) X 1-03 
(jS-phenyl), which equals 432-4, the decimal part having no significance on 
account of the factors being correct only within one-half per cent. 
In order to simplify the subsequent calculations, some of the factors 
may be multiplied together to begin with, thus giving useful subsidiary 
factors. 
Thus : a-carbinol, CHOHa, = 0-92 X 1-10 = 1-01 
P- „ CHOHjS, = 1-15x1-035 = M9 
* Observation agrees with this. 
t As found before in Part XIII, A, of table on p. 36. 
