OP ARTS AND SCIENCES. 89 



VII. 



NOTE ON A CRITICISM OF THE AUTHOR'S APPAR- 

 ATUS FOR FRACTIONAL CONDENSATION.* 



By C. M. Warren, 

 Professor of Organic Chemistry, Massachusetts Institute of Technology. 



The supplement of the American edition of the Chemical News 

 for February, 1869, contains an article on ''Cracking of Petro- 

 leums," hy the editor of the supplement, which closes with the 

 following paragraph : — 



" In conclusion, we offer the suggestion to those who analyze oils 

 hy fractional distillation that they take pains to avoid the condi- 

 tions which favor cracking; by not observing such caution the 

 analyses of petroleums hitherto made have generally been vitiated, 

 in fact, very many have been worthless. Perhaps it is not possible to 

 avoid all the error that may arise from cracking, yet it may easily 

 be brought so low as to be insignificant. Of the apparatus which 

 has been devised for fractional distillation probably the one least 

 suitable for petroleums and other unstable liquids is that of Prof. 

 C. M. Warren. Warren's still probably answers well enough for 

 alcohols, essential oils, and the benzole series, but cracking can 

 scarcely be avoided when it is used for petroleums." 



I am induced to notice the above criticism from the fact, to which 

 it recalls my attention, that the question of adaptability for the 

 separation of bodies more or less liable to decomposition by heat in 

 distillation, as compared with that of the common forms of distilla- 

 tory apparatus, was not specially considered in my memoir descrip- 

 tive of my process,! an omission which, it now appears, it might 

 have been better not to have made. It was not, however, from 



* It would appear that this article was written in 1869. Two manuscript 

 copies of it were found among the author's papers after his death, viz. a rough 

 draft, and a fair copy ready for the printer's hands. The latter is here printed, 

 without change. 



t Memoirs of the American Academy, 1864 ; American Journal of Science, 

 1865; Chemical News, 1865. 



