between the viscositt of liquids and their chemical nature. C57 
Compounds Differing by a Carbon Atom. 
1 
,)rV\ 
Diff. 
rP. 
Diff. 
Tetrachlormethane . 
Tetraclilorethylene . 
406 
496 
90 
Methyl alcohol 
Aldehyde . 
126 
169 
48 
As in the case of molecular viscosity, the different values given by the comparisons 
may be partly due to the fact tliat the addition of a carbon atom to form the group 
C : C exerts a different effect from that produced when the carbon atom added 
forms the group C : O, and partly to the presence of molecidar aggregates in the 
methyl alcohol. 
Isomers. 
Normal and Iso compounds. 
Normal. 
Difference. 
Iso. 
>lP. 
Pentanes . 
329 
9 
320 
Hexanes. 
415 
10 
405 
Heptanes. 
495 
13 
482 
Propyl iodides. 
425 
8 
417 
Propyl bromides. 
353 
7 
346 
Propyl chlorides. 
294 
4 
290 
Butyric acids. 
397 
- 1 
398 
With the exception of the butyric acids, which are anomalous, probably for the 
reason already given, the normal compound has always the higher viscosity, the 
average difference being about 8 units. It is evident, however, that in the same 
family of compounds the difference tends to rise with the molecular weight. 
Aromatic Hydrocarbons. 
//#. 
Diff. 
Ortho-xylene. 
483 
- 8 
Ethyl benzene. 
475 
- I 
Meta-xylene. 
474 
-7 
Para-xylene. 
467 
As in the case of molecular viscosity, ortho-xylene has the largest value and para- 
MDCCCXOIV.'—A. 4 P 
