BETWEEN THE VISCOSITY OF LIQUIDS AND THEIR CHEMICAL NATURE. 405 
OsTWALD and Arrhenius (•'Zeits. flir pliysik. Chemle,’ vol. 7, p. 285, 1887). The 
greater number of the determinations were made at the temperature of 20°, but in 
the cases of formic and butyric acids, and in those of methyl, ethyl, propyl, iso-propyl, 
and iso-butyl alcohols, a series of estimations at every 10° between 10° and 50° was 
made. 
Gartenmeister finds that although, in general, viscosity may be said to increase 
with molecular weight, there are apparently numerous exceptions to this rule. These 
are seen not only among the initial members of the fatty acid series, but also among 
the esters of aceto-acetic acid. Metameric esters frequently possess different vis¬ 
cosities, as already observed by Rellstab, On the other hand, Rellstab’s con¬ 
clusion that the viscosities more nearly approximate the smaller the difference in 
boiling-point is only generally true. On comparing the boiling-points of the aceto- 
acetic esters with their viscosities, it is found that the boiling-point of the ethyl ester 
is always an equal number of degrees higher than that of the methyl ester of the same 
acid, whereas, in the case of the viscosities, the relations are of quite another order. 
Bruhl (‘Ber.,’ 13, 1529) has pointed out that it is probable that in the case of 
isomeric bodies more time would be required for an equal number of molecules to flow 
through a capillary tube of that particular compound which has the higher boiling- 
point, the greater relative density, and the greater refractive index ; or, in other 
words, that the viscosity of a licpiid stands in the same relation to its chemical 
constitution as do its other physical constants. Gartenmeister finds that, although 
the statement may be taken as generally true, there are numerous exceptions. 
Rellstab concluded that substances containing so-called double-linked carbon 
transpire more slowly than those of equal molecular weight containing single-linked 
carbon. Prjbrajvi and Handl, however, found that the “ specific viscosity ” of allyl 
alcohol (CgHgO) is less than that of propyl alcohol (CgHgO), and Gartenmeister 
observed that diallyl CHg : CH(CH 3 ) 2 CH : CHg has a lower viscosity than dipropyl 
CH 3 (CH 3 )j,CH 3 . On the other hand, the viscosity of benzene (GgHg) is more than 
double that of dipropyl. If it is assumed that there is double linking in both allyl 
compounds and in benzene, it would seem to follow that the relatively high viscosity 
of benzene cannot be ascribed wholly to double linking, but is dependent rather on 
those properties that we associate with the ring mode of atomic grouping. This view 
of the influence of the ring grouping is confirmed by the study of other aromatic 
compounds. 
Gartenmeister further concludes from Pribram and Handl’s observations that, 
within the limits of temperature at which the determinations have been made, the 
viscosity of compounds containing an equal number of carbon atoms in which Cl, Br, 
and I replace each other is proportional to the molecular weight. In the case of 
homologous series the viscosity is proportional to the square of the molecular weight. 
The introduction of the hydroxyl group into the molecule greatly increases the 
viscosity of the liquid. This is strikingly illustrated by the instances of propyl 
