﻿1008 Research Staff o£ the G. E. C, London, on 



The essential features were the viscosimeter, the surface 

 tension apparatus, and the drawing device. 



(a) Viscosimeter. — The viscosity was measured directly by 

 means of the torsional force exerted on a flat disk by another 

 disk parallel and near to it when both are immersed in the 

 liquid and when the second disk is made to rotate at a fixed 

 speed. If the geometrical arrangement is unaltered the 

 torsional force will be proportional to the viscosity of the 

 liquid and to the velocity. 



A is a metal vessel containing the liquid and surrounded 

 by a thermostat B containing glycerine. Through the 

 bottom of this vessel passes a spindle C to which a pulley is 

 fixed driven by a small motor. 



To the top of is attached the rotating disk E in the 

 centre of which is a jewelled bearing. Above this is the 

 fixed disk separated from it and supported by a hardened 

 steel point resting in the jewelled bearing. A light steel 

 spindle F passing loosely through the metal cover serves to 

 keep the fixed disk parallel to E and to connect it with a 

 torsion measuring device consisting of a spiral steel spring H 

 and an aluminium pointer G which moves over a graduated 

 scale on the metal cover. 



Vanes D are also attached to the spindle which serve to 

 stir the liquid by causing it to rise through vertical channels 

 in the metal cylinder K and to fall over the top of K back 

 into the bath. The bottom of K is bevelled as shown, so 

 that if the liquid contains suspensions these will fall in 

 between the vanes and thus be kept from settling. 



The thermostat can be heated by means of the gas ring 

 burner placed below it. 



(a) The viscosimeter was calibrated by means of solutions 

 of known viscosity. A 60 per cent, sucrose solution was 

 found exceedingly useful for this purpose, as it gives a wide 

 range of viscosities with temperature change, and the 

 viscosities at various temperatures have been accurately 

 determined by the Bureau of Standards *. 



It was found that the scale deflexions for a given speed 

 of the rotating disk were directly proportional to the viscosity, 

 and also that for a given viscosity the scale deflexions were 

 directly proportional to the speed of the rotating disk over a 

 wide range. 



(b) Surface Tension Apparatus. — The surface tension 

 apparatus was measured by Willi elmy's method, viz. by 

 means of the force required to break the film drawn out o£ 



* E. C. Bingham and R. F. Jackson, Bureau of Standards Bulletin, 

 No. 14, p. 59 (1917). 



