8 ART. S. — S. KAWAMUEA : COAGULATION OF COLLOIDAL 



colloidal solutions of ferrie and aluminium hydroxide prepared 

 by dialysis. Hence coagulation phenomena similar to those ob- 

 served in the latter solution are to be expected in the present 

 study. 



3. The Method of Measurement. 



The apparatus and the method of measuring viscosity em- 

 ployed in this work are those recommended by Ostwald ; they 

 are too well known to require description. A capillary tube of 

 a rather wide bore was purposely chosen for the viscosimeter in 

 order to minimise the effect of small particles which might 

 separate out from the solution and adhere to the side of the 

 tube. This had the unfortunate result of making the flow of 

 the liquid too rapid and so the correction to be applied on 

 account of the kinetic energy acquired by it became unduely 

 large. But as it is quite useless to aim at any high degree of 

 exactness in a work of this nature, this correction has been 

 neglected. The omission is the more justifiable as the viscosity 

 is measured not for its own sake but only as an index to the 

 degree of coagulation, and so only relative values are to be 

 considered. For the same reason the time of flow was measured 

 with an ordinary watch, the readings being taken to the second. 



As the temperature exercises considerable influence on vis- 

 cosity, the apparatus was immersed in a thermostadt with glass 

 sides. The temperature was kept constant at 25°, and the greatest 

 fluctuation during the whole period of the work, which lasted 

 several months, did not exceed 5 of a degree. 



To make a measurement, 2 c.c. of the colloidal solution and 

 an equal volume of an electrolyte solution were introduced into 



