Peideaux. — On Kauri-resin. 375 



to combined and H. At the beginning of the distillation 

 the conditions must favour the formation of water, since most 

 of the water is given off just before 100 and up to about 200. 

 After this the proportion of water in the distillate grows 

 negligible. This loss of combined water at an early stage is 

 evidently responsible for the fact that we get a very small 

 proportion of oxidized products in the distilled oils, although 

 the resin itself is a very highly oxidized substance, approxi- 

 mating to the molecular constitution C 2n H 3n O n by a combustion. 

 The escaping gases are thus oxidized at or before the moment 

 of liberation, water being separated. This view accounts for 

 the fact that the first runnings of the distillate consist of more 

 unsaturated carbon-compounds, while the later portions are 

 more saturated.* The few bromine numbers I have obtained 

 for the oils bear this out. The total absorptions of bromine 

 decrease as the boiling-points of the distillates rise, but the 

 absorption- figure in the second column! decreases still more 

 remarkably, for the substituted bromine calculated as HI 

 remains nearly constant through the oils experimented with, 

 which, of course, makes the rise in bromine-absorption less 

 abrupt when we take the first column in the table than when 

 we take the second. The first products, even if saturated, 

 would be deprived of some of their H to form water and an 

 unsaturated compound. As the distillation proceeds the O 

 has nearly all been got rid of as water, so there is now no 

 reason why unsaturated compounds should be produced rather 

 than saturated. This accounts for the large drop in the 

 bromine-absorption observed by Mills in the case of ordinary 

 resin-oils between the last of the spirit-like distillate and the 

 beginning of the medium oil. This is the point where the 

 proportion of water in succeeding fractions dwindles almost 

 to nothing. Even now, however, it is probable that the for- 

 mation of unsaturated compounds is favoured by the small 

 proportion of H left relatively to C. We started with the 

 composition C 2n H 3n O n ; nearly all the has been removed as 

 H.,0, so we are left with C 2n H n as the basis from which to 

 form the remaining distillate. So at high temperatures the 

 bromine-absorption of the distillate hardly decreases, and re- 

 mains stationary in the last runnings. We should expect an 

 increase, if anything, at the end — that is, if all the resin is to 

 come over as oil. But if the distillation is pushed to the end 

 there is a residue of pure C, so we must suppose that the un- 

 saturated bodies which would have to be formed to bring over 

 all the C in the combined state are not stable at such high 



* Mills has proved this in the case of ordinary resin-oil by the 

 bromine-absorption, whici begins at a maximum and decreases with 

 the higher fractions. 



t Calculated as I have explained above in the case of the resins. 



