Rotatory Polarisation of Liquids, 415 



§ 5. Determination of the Magneto -rotatory Powers of some 

 Isomeric Liquids. 



M. Berthelot had kindly given me, in the spring of 1869, a 

 certain quantity of two isomeric liquids ; but not having prepared 

 them himself, he took care to tell me that he did not guarantee 

 their perfect purity. They were ethylvaleric ether and amyU 

 acetic ether, both having the general formula C 14 H 14 O 4 . Sub- 

 mitted several times, and at different periods, to experiment, the 

 second always exhibited a stronger magneto-rotatory power than 

 the first. The most accurate experiments gave 0*877 for the 

 specific magneto-rotatory power of the first, and 0*895 for that 

 of the second. When I wished to compare their rotatory powers 

 with their densities, I was much embarrassed on account of the 

 difficulty of ascertaining these densities. Thus, according to 

 M. Delffs, the density of amylacetic ether is 0'863 at 10°, and 

 according to M. Kopp 0*8837 at 0°. The density of ethylvaleric 

 ether is, according to M. Delffs, 0*870 at 13°*5, and according 

 to M. Berthelot himself 0*869 at 14°. On the other hand, M. 

 Adolphe Perret (who was so obliging as to determine for me the 

 densities of most of the liquids I used in my researches) found 

 for the density of both the ethers in question at 16° the number 

 0*870; so that the samples upon which I operated had, appa- 

 rently, the same density ; the very perceptible difference, there- 

 fore, presented by their rotatory powers cannot depend upon a 

 difference of density. Besides, if either the density attributed 

 to amylacetic ether by M. Delffs or that attributed by M. Kopp 

 were taken, this would not be sufficient to explain the superiority 

 of its magneto-rotatory power. There is probably, then, in the 

 different molecular grouping presented by these two isomeric 

 liquids a cause of the greater magneto-rotatory power of amyl- 

 acetic than of ethylvaleric ether. 



Subsequently having been obliged by M.Wurtz with speci- 

 mens of some isomeric liquids prepared by himself, I was enabled 

 to extend the field of my investigation. Besides the acetate of 

 amyle and valerate of ethyle which I had already submitted to 

 experiment under the names of amylacetic ether and ethylvaleric 

 ether, M. Wurtz sent me a specimen of hutyrate of isopropyle, 

 which is isomeric with the two others. The general formula of 

 these three compounds is, according to the notation adopted by M. 

 Wurtz, who doubles the number for hydrogen, C 7 H H 2 instead 

 of C 14 H 14 O 4 . Following the system adopted by M. Wurtz, the 

 formula becomes : — 



For acetate of amyle, C 2 H 3 (C 5 H 11 ) O 2 : 



For valerate of ethyle, C 2 H 5 (C 5 H 9 ) O 2 ; 



For hutyrate of isopropyle, C 3 H 7 (C 4 H 7 ) O 2 . 



