Viscosity of Solutions, 277 



mark to that when it crossed the lower mark was caught in a 

 weighed flask and immediately weighed. 



The only disadvantage of the use of corks instead of making 

 the whole glischrometer of glass and sealing the capillary and 

 limbs together, is that a ring of rubber 8 millim. in mean 

 diameter and 0*5 millim. in width is in contact with the 

 liquid at each end of the capillary tube ; but in the case of 

 aqueous solutions there is nothing to fear in the way of 

 dissolved rubber. By the use of corks, on the other hand, in 

 addition to the fact that the constants of the glischrometer can 

 be evaluated before uniting the limbs and capillary, we have 

 the further advantages that cleaning operations are much 

 facilitated, risk of breakage is diminished, and capillary tubes 

 of different dimensions can readily be substituted if necessary. 



The following values were obtained for the constants : — 



Semi-major-axis of capillary (A) =0*012165 cm. 



Semi-minor axis of capillary (B) =0*011525 ,, 



Mean diameter of capillary (D) =0*023681 „ 



Length of capillary . . (L) =5*3570 „ 



Couette correction to length (/) =0*0190 „ 

 Working length of capillary (L + /) = 5*3760 „ 



Volume of right limb , . (Vr) = 5*240 c. cm. 



Volume of left limb . . . (Y L ) =5*211 „ 



The formula from which the values of the viscosity are 

 found is 



7rA 3 B g G/)AT ABV 8 n 



v ~4Y(A.* + B*)(L + l) 4tt(A 2 + B 2 )(X + t 



where the second term represents the kinetic-energy cor- 

 rection, and 



7] is the viscosity coefficient, 



G is the value of the acceleration due to gravity, 



p is the density of water in the water-manometer, 



h is the height of water in the manometer, 



T is the time taken for volume V to flow through the 

 capillary under pressure G p h, 



8 is the density of liquid under observation at the par- 

 ticular temperature ; and 



(l + 23t) is the correcting term for expansion of the glass, 

 where ,6 is the linear coefficient of expansion, and t is 

 the temperature of the experiment. 



The formula then becomes 



v = ccXpxhxT-l3x jj x (1 + 2/30, 

 Phil. Mag. S. 5. Vol. 49. No. 298. March 1900. U 



