BETWEEN THE VISCOSITY OP LIQUIDS AND THEIR CHEMICAL NATURE. 635 
Normal Propyl and Allyl Compounds. 
Normal pro])yl. 
Difference. 
Allyl. 
Tjd^. 
ijd?. 
Hydrocarbons. 
818 
(45) 
728 
Iodides . 
903 
39 
864 
Bromides. 
774 
40 
734 
Chlorides. 
658 
41 
617 
Ethylene and Acetylene Bromides. 
Ethylene 
Acetylene. 
Bromides. 
973 
41 
932 
It is evident that a normal propyl compound has a molecular viscosity which is, on 
the average, 41 units greater than that of the corresponding allyl compound. It is 
further indicative of the comparatively definite quantitative relations here exhibited 
that the difference between the molecular viscosities of ethylene and acetylene 
bromides, which are related in the same way as a normal propyl compound is to an 
allyl compound, is also 41 units. 
Isologous Hydrocarbons. 
C„H2„. 
C„H 
2^ — 2* 
CnHoti — g* 
Difference. 
Difference. 
1 
Difference. 
,]d^. 
5 
687 
22 
665 
67 
620 
6 
818 
90 
728 
130 
688 
7 
931 
110 
821 
8 
1035 
* • 
• • 
• • 
• • 
96 
939 
Loss of hydrogen is always attended by a fall in molecular viscosity. On comparing 
two series of corresponding hydrocarbons, the differences, although not quite 
constant, vary within comparatively narrow limits ; in the case of the aromatic hydro¬ 
carbons and the paraffins, the differences vary in a regular way, and diminish with 
rise in molecular weight. It is also evident that the removal in succession of two 
hydrogen atoms from a saturated hydrocarbon brings about a variable decrement in 
viscosity. 
4 M 2 
