90 PROCEEDINGS OF THE AMERICAN ACADEMY 



oversight that this was omitted, hut because it was thought that 

 no one could fail to see. on a moment's reflection, that the condi- 

 tions to which liquids are subjected in my apparatus, so far as 

 these may be of a nature to affect the liability to decomposition, 

 are quite the same as those attending fractional distillation by the 

 common process. It was therefore deemed sufficient to make no 

 further allusion to this matter than was done, indirectly, in recom- 

 mending my process for the separation of "bodies not decomposed 

 by heat in distillation " (p. 134 of the original memoir), clearly 

 implying that I did not regard it as faultless for the opposite class 

 of substances; and sufficient, it would seem, to put any one on his 

 guard who would make such use of it. Nevertheless, as I hold that 

 my process introduces no new condition favorable to decomposition, 

 even of bodies liable to partial change of this nature during distil- 

 lation, I do not hesitate to recommend it also as preferable to the 

 old process for this very class of substances, — when distillation 

 cannot be altogether avoided, — since the length of time required 

 to effect an equal or better separation may thereby be very much 

 shortened, and consequently the aggregate amount of decomposition 

 materially and proportionately lessened. But in operating upon 

 such substances it would be unadvisable to continue the process 

 longer than absolutely necessary to obtain the best approximation 

 to the desired result which the nature of the material would admit 

 of; and the same is of course true of the old process. 



Not to enter into much detail, it may be stated that the only 

 essential difference between my apparatus and that in common use 

 for fractional distillation consists in the elevated condenser which I 

 interpose between the retort and the ordinary condenser, discharg- 

 ing itself backward into the retort, its temperature being regulated 

 by a separate flame, and maintained a few degrees (more or less, 

 according to the nature or purity of the substance to be distilled) 

 below the temperature of the retort. 



In other forms of apparatus, there being no regulated condenser 

 to effect a separation of the mixed vapors that escape from the re- 

 tort, the whole of these go forward and are condensed together, the 

 resulting liquid falling into the receiver. 



Both in my process and in the common process the liquid in the 

 retort is simply maintained in a state of ebullition under atmos- 

 spheric pressure; consequently it is no more favorably conditioned 

 for decomposition, in respect to temperature, in the one case than 

 in the other. 



