G66 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
Molecular Viscosity Work at Slope ‘04323 —(continued). 
Observed. 
Calculated. 
Difference 
per cent. 
Methyl sulphide. 
‘240 
236 
1-7 
Ethyl sulphide. 
393 
396 
-0-8 
Alethyl ethyl ketone .... 
302 
301 
0-3 
Methyl propyl ketone .... 
383 
381 
0-5 
Diethyl ketone. 
376 
381 
- 1-3 
Formic acid. 
160 
159 
0-6 
Acetic acid. 
237 
239 
- 0-8 
Propionic acid . . . . 
323 
319 
1-2 
Butyric acid. 
397 
399 
- 0-5 
Isobutyric acid. 
398 
391 
1-8 
Acetic anhydride. 
394 
393 
0-3 
Propionic anhydride .... 
542 
553 
- 2-0 
Ethyl ether. 
‘295 
295 
0-0 
Benzene . 
314 
315 
- 0-3 
Toluene. 
395 
395 
0-0 
Ethyl benzene. 
475 
475 
0-0 
Ortho-xylene. 
483 
475 
1-7 
Meta-xylene. 
474 
475 
- 0-2 
Para-xylene. 
467 
475 
- 1-7 
The average difference between the observed and calculated numbers given by the 
above compounds is less than 1 per cent. ; in one or two cases, as the isomeric ketones 
and isomeric xylenes, the differences are partly due to effects of constitution which are 
ignored in obtaining the calculated values. 
Several compounds are worthy of special discussion, and are considered in what 
follows. 
IsojJT'ene .—The calculated value for isoprene is deduced on the assumption that it is 
a straight chain compound containing two double linkages. Of the five possible 
formulEB for isoprene (see Tilden, ‘ Proc. Birmingham Phil. Soc.,’ vol. 8, 1892), one 
contains, in addition to the double linkages, an iso linkage of carbon atoms. If an iso 
linkage occurred in the chain the calculated value for the molecular viscosity work 
would be reduced to 270, and the difference between the observed and calculated 
values raised to 14 units, or 5 per cent. Viscosity observations therefore favour the 
view which is indicated by chemical methods, that no iso linkage occurs in the 
