366 REPORT—1905. 
have been carried out at one temperature, and, as the result of these determina- 
tions, it has been found that the viscosity-composition curve for binary mixtures 
may exhibit a maximum or minimum of viscosity, or may be an almost straight 
line joining the values for the viscosity of the pure liquids. - 
In the present investigation the viscosities of the mixtures were determined at 
the temperature of the boiling-point of the mixture, in which case it was expected 
viscosity curves would be obtained similar in form to the boiling-point curves, and 
that maxima and minima in the boiling-point curve would be represented by 
minima and maxima respectively in the viscosity curve. In the case of benzene 
and methyl alcohol, the viscosities of which at the respective boiling-points are 
nearly the same, this expectation appears to be realised. Where the viscosities 
of the pure liquids at their boiling-points are not the same certain complications, 
not yet fully worked out, are met with. 
In addition to the preceding line of investigation, it is proposed to study also 
the ‘mean molecular weight’ of the mixture, with a view to ascertaining the 
effect of association in the production of irregularities in the viscosity curve, 
5. Report of the Committee on Wave-length Tables of the Spectra of the 
Elements and Compounds.—See Reports, p. 105, 
6. Report of the Committee on the Study of Hydro-aromatic 
Substances.—See Reports, p. 153. 
FRIDAY, AUGUST 18. 
The following Papers and Report were read :— 
1. A South African Mineral Spring. 
By Professor P. D. Haun, Ph.D., M.A. 
Yhe thermo-chalybeate spring at Caledon is the most remarkable of its kind 
in the British Empire. The spring yields daily 150,000 gallons of water, and the 
temperature of the water at the eye of the spring is 120° F. (49° C.),. The water 
was found to have the following composition, One thousand parts of water con- 
tain :— 
Hydric ferrous carbonate . ‘ : : - . . 0-0460 
Sodic sulphate . : ; : : : . 4 - 0:0123 
Common salt - : : - : : ‘ : » 0:0575 
Silica . : : ; : 5 . : : cE . 0:0257 
Alumina. : ‘ : : : : : ‘ - 00108 
Calcic sulphate . : : : ; : : : - 0:0232 
» carbonate . c 3 S 5 ; : . trace 
Magnesic sulphate. " : : 2 : 3 « 0:0150 
Potash. : = . 5 j . 3 ‘ . . trace 
Total mineral ingredients. ; : . - 01905 
. 
In judging a chalybeate water the important point is whether the physiological 
and therapeutical effect of the use of the water has definitely proved that the iron 
compounds in the water have been absorbed into the system. The quantity and 
quality of the accompanying constituents, rather than the absolute quantity of the 
iron compounds in a water, decide whether it is to be counted among the chaly- 
beate waters. In the Caledon water the accompanying saline constituents 
which come into account—viz., common salt, sodic sulphate, and magnesic 
sulphate—form only a very small quantity, which does not in the least prevent 
