J. H, Long—Indices of Refraction of Compound Ethers. 285 
Making the necessary calculations I find the values as in the 
following table: 
Bp dao Nao 
§ Methyl butyrate ....-_. 103-104° ‘8976 13889 
Methyl isobutyrate _..- - 90° *8893 1:3840 
§ Ethyl butyrate._....... 114° 8906 13960 
Ethyl isobutyrate ...... 107° “8697 1°3880 
§ Isobuty] butyrate ...__- 155° 8627 1°4045 
Isobutyl isobutyrate .... 144-145° "8575 1:3999 
utyrate 178° "8646 1:4110 
| Amyl isobutyrate -....- 166° "8580 1:4076 
As might be expected, the constants in the case of the iso 
compounds are in every instance lower than in those of the 
corresponding normals. Here as in several compounds exam- 
ined by Briihl, the characteristic differences of ethers of nor- 
mal and iso acids are seen to extend to their action on light. 
It will not be without interest to find what values for the 
m—1 diff. for 
u("7) 
d CH, 
Methyl formate.....- O,H4O. 21-28 
Propyl formate .._. Neh ae us 7°65 
Methyl propionate Dol hs 
Ethyl propionate __ 799 
Isobutyl fo 6.2 Os 44°56 
es iso u a 7-16 
ropyl propionate __ Fe 
a: Mebane t CoHi202 1A RR 
Sobutyl propionate 
Propyl isobutyrate_ t OrH140s — 
es propionate fae 8-16 
uty! butyrate__ 5 
Isobutyl isobutyrate CeHi60a ae 
Propyl valer. tec: 
Amyl butyrate ___. T14 
Amyl isobutyrate._ | ©,H,.02 75-06 
Isobutyl valerate __ a 
Mean diff. for CH, = 7°69. 
Tt thus appears that the differences for CH, from group to 
Oup are not quite constant, but the variations are not greater 
| 
09, &” S.09 
or 
Ww . 
5°90, 5°81, 6-11, 5-58, 5°38, 5°80 and 5°85. Of course it is not 
intended that these numbers represent the atomic refraction in 
