between the viscosity oe liquids and their chemical nature. 443 
A romatic Hydrocarhons. 
Benzene. 
.C,H,. 
Toluene (Methyl benzene) . 
.C,H,.CH3. 
Ethyl benzene. 
.C3H3.C,H,. 
Ortho-xylene. 
.C,H,(CH3),(1;2). 
Meta-xylene. 
.C 3 H,(CH 3 ),( 1 : 3 ). 
Para-xylene. 
.C 3 H,(CH 3 ),(I: 4 ). 
Alcohols. 
Methvl alcohol .... 
...... CH30H'. 
Ethyl alchohol .... 
. CHg.CbLOH. 
Propyl alcohol. 
.CH3.CH3.CH,on. 
Isopropyl alcohol .... 
.. (CH3)3CH0H. 
Butyl alcohol. 
. CH3.(CH3)3.CH30H. 
Isobutyl alcohol .... 
. (CH3)3CH.CHoOH. 
Trimethyl carbinol . 
. (CH3)3C0H. 
Amyl alcohol (active) 
. CH3.CH3.CH(CH3).CH30H. 
Amyl alcohol (inactive). 
. (CH3)3CH.CH2.CH30H. 
Dimethyl ethyl carbinol 
. (CH3)3C(0H).CH3.CH3. 
Allyl alcohol. 
. CHaiCH.CkLOH. 
Of course such a list might be greatly extended, and might be made to comprise 
other well-defined groups of correlated substances. It must, however, be remembered 
that we are limited in our selection by the difficulty of obtaining many substances in 
a state of sufficient purity to warrant the expenditure of the labour necessary to 
determine their viscosity. Moreover, we were desirous that the upper limit of 
temperature in our observations should not exceed that which could be converdently 
ascertained in a glycerin bath : hence the boiling-point should not be higlier than 
160° or 170° 
PART II.—RESULTS OBTAINED. 
Water. 
The viscosity of water has been frequently measured ; indeed, no other liquid has 
been made the subject of so many determinations of this property. As the measure¬ 
ments hitherto published extend, for the most part, over a comparatively limited range 
of temperature, we have considered it desirable to make an additional series of observa¬ 
tions from about 0° up to the ordinary boiling-point, partly to gain more information 
as to the effect of temperature in altering the viscosity of water, and partly to 
3 L 2 
