599 
Calculating however with the same value of x the proportion of 
the nitro-m-chlorotoluenes formed by the nitration of m-chlorotoluene, 
there is no such gratifying concordance. This is due to the fact, 
CMs that in this case the two substituents act no longer independ- 
ZN ently of each other, but that both methyl and chlorine 
| 3| direct the entering nitro group to the places 2, 4, and 6. 
A, Now we must not simply add the figures for the isomers, 
but we must take the resultant of their action, as is indicated in 
the scheme below, in which it is assumed that the benzene nucleus 
is a regular hexagon. 
a 
If we calculate in this way the proportion of the isomers, we find 
indeed a gratifying concordance between calculation and experiment: 
CH, CH, 
Ee 
tal one. soo 
21 Sla | “slo 
Ne NA 
25.9 32 
calculated found 
Amsterdam, org. chem. lab. of the Univ. October 1912. 
Physics. — “On the polarisation impressed upon light by traversing 
the shit of a spectroscope and some errors resulting there- 
Jrom.” By Prof. P. Zeman. 
In a communication “The intensities of the components of spectral 
lines divided by magnetism” '), I drew attention to the fact that 
by the polarizing action of the grating the ratio of the observed 
intensities of the components of a triplet differs considerably from 
1) These Proceedings, October 26 1907. 
