OF ARTS AND SCIENCES. 91 



The elevated condenser being kept at a lower temperature than 

 that of the retort, it seems needless to say, has no effect to raise 

 the temperature of the latter, hut, on the contrary, holds it in 

 check; and by proper management may serve to secure the condi- 

 tions most favorable for taking off the largest possible quantity of 

 the most volatile constituent at any time present, and this at the 

 lowest possible temperature, not only of the vapor to be collected, 

 but also of the liquid in the retort, — operating therefore advanta- 

 geously, rather than unfavorably, with respect to decomposition. 

 And yet I suspect, as he does not specify, that this is the identical 

 feature of my process — being its chief or only distinctive feature — 

 which has occasioned nry critic's misconception with regard to the 

 utility of the apparatus. It would evidently require a considera- 

 bly longer time to distil a given quantity of a mixture of liquids 

 of different boiling-points in my apparatus, if used as recom- 

 mended for stable liquids, than in the common form, since in a 

 single operation the larger part of the mixture is in reality many 

 times condensed and re-distilled. Can this be his stumbling-block, 

 — that he has not taken into consideration the relative amount of 

 actual work (not measurable, however, by the quantity of liquid 

 distilled, but by the degree of purity of the products obtained) that 

 may be done with this apparatus in a given time as compared with 

 the common apparatus? 



If the liquid is not subjected to a higher temperature in the one 

 apparatus than in the other, it is evident that superiority on the 

 score of decomposition must be awarded to the one capable of giv- 

 ing the best results in the shortest space of time, since the amount 

 of decomposition must be proportional to the time occupied. If 

 objection is made to the repeated condensation and re-distillation 

 that take place in my apparatus, I have only to say that this is a 

 necessary condition of any effective process of fractional distilla- 

 tion; and if, to avoid cracking, this condition must be abandoned, 

 and the vapors, as they rise laden with impurities, are immediately 

 condensed in the receiver, then must fractional distillation itself 

 be abandoned as a worthless process. 



It has probably escaped my critic's scrutiny that my apparatus 

 does not require to be employed in precisely the manner that I 

 recommended for stable liquids; and a judicious chemist would 

 modify the conditions to suit the nature of the material to be ex- 

 amined, — I refer to the adjustment of the temperature of the ele- 

 vated condenser. In operating on perfectly stable liquids, I have 



