114 REPORTS ON THE STATE OF SCIENCE. 



of cases the proportions in which the isomerides are in equilibrium can be 

 determined by means of solubility measurements. Photographs have 

 therefore been taken of the absorption spectra of the majority of the 

 camphor-derivatives which have formed the subject of previous investiga- 

 tions, and we are now in a position to summarise the principal results 

 that have been obtained. 



Halogen-derivatives of Camphor. 



(1) The camphor band observed by Baly and by Hartley at a concen- 

 tration of N|10 piactically disappears when the concentration of the 

 alcoholic solution is reduced to N|1U0 (thickness of liquid 250 to 2 5 inm.), 

 but can be restored by the addition of alkali. /j-Bromocamphor, 



/CH, 

 C«H,3Br/ I 



at a concentration cf NjlCO behaves in the same way as camphor. 



(2) a-Chlorocamphor and a-bromocamphorat a concentration of N|100 



show a band in the same position (-- 3400] as the camphor band. 



The band is eliminated when the second a -position is occupied by 

 bromine or by a nitro group, but remains unaffected when the halogen is 

 introduced in the /3 or in the tt position. 



(3) No marked change in persistence is produced by the addition of 

 alkali to a-chlorocamphor, a-bromocamphor, or their /3 and ir bromo- 

 derivatives. All these compounds are quite stable when alone, but 

 undergo isomeric change rapidly in presence of a small proportion of 

 alkali. It is therefore evident that in this case at least there is no 

 direct quantitative relationship between the velocity of isomeric change 

 and the persistence of the absorption band. 



Kitro-derivati ves. 



(4) Nitrocamphane shows no absorption band, whether the solution 

 be prepared by dissolving the crystals of the normal form or by adding 

 acid to the sodium salt of the pseudo form. Even in presence of ten 

 equivalents of alkali no definite band is developed. It is therefore clear 

 that dynamic isomerism, even of a well-pronounced type, is not neces- 

 sarily associated with the production of a band. 



(5) Nitrocamphor dissolved in alcohol shows a shallosv band at 



— 3000 ; it differs in position from that produced by bromocamphor — 

 A 



a result that is in accord with the view, consistently advocated, that the 



mobile hydrogen atom in this compound wanders to the nitro and not 



to the carbonyl group. The band disappears in the a-chloro and ti bromo 



derivatives, and also in the anhydride derived from the pseudo form by 



loss of water ; its occurrence appears, therefore, to be limited by the same 



conditions as those which determine the occurrence of isomeric change. 



(6) In marked contrast with the behaviour of the — CHX-CO — 

 compounds described above, the nitrocamphor band is enormously inten- 



