Tables 169-171 



TABLE 169. — Viscosity of Fluids and Solids 



205 



The coefficient cf viscosity of a substance is the tangential force required to move a unit area of a plane surface 

 with unit speed relative to another parallel plane surface from which it is separated by a layer a unit thick of the sub- 

 stance. Viscosity measures the temporary rigidity it gives to the substance. The viscosity of fluids is generally meas- 

 ured by the rate of flow of the fluid through a capillary tube the length of which is great in comparison with its diameter. 

 The equation generally used is 



ju, the viscosity, = ■ I h > 



I28Q(/+X) V * / 



where y is the density (g/cm 3 ), d and / are the diameter and length in cm of the tube, Q the volume in cm 3 discharged 

 in t sec, X the Couette correction which corrects the measured to the effective length of the tube,/; the average head 

 in cm, m the coefficient of kinetic energy correction, mi a /g, necessary for the loss of energy due to turbulent in distinc- 

 tion from viscous flow, g being the acceleration of gravity (cm/sec/sec), v the mean velocity in cm per sec. (See Tech- 

 nologic Paper of the Bureau of Standards, ioo and 112, Herschel, 1917-191S, for discussion of this_ correction and X.) 



The fluidity is the reciprocal of the absolute viscosity. The kinetic viscosity is the absolute viscosity divided by 

 the density. Specific viscosity is the viscosity relative to that of some standard substance, generally water, at some 

 definite temperature. The dimensions of viscosity are ML l T~ l . It is generally expressed in cgs units as dyne-seconds 

 per cm 2 or poises. 



The viscosity of solids may be measured in relative terms by the damping of the oscillations of suspended wires 

 (see Table 82). Ladenburg (1906) gives the viscosity of Venice turpentine at 18.3° as 1300 poises; Trouton and 

 Andrews (1904) of pitch at 0°, 51 X io 10 , at 15°, 1.3 X io 10 ; of shoemakers' wax at 8°, 4.7 X io 6 ; of soda glass at S75°. 

 11 X io 12 ; Deeley (1908) of glacier ice as 12 X io 13 . 



TABLE 170. — Viscosity of Water in Centipoises (Temperature Variation) 



Bingham and Jackson, Bulletin Bureau of Standards, 14, 75, 1917. Pressure effect, see p. 652. 



Vis- 

 cosity, 

 cp 



1. 7921 

 I-73I3 

 1.6728 

 1.6191 

 1.S674 



1.5188 

 1.4728 



1.4284 

 1.3860 

 1.3462 



Vis- 

 cosity, 

 cp 



0.4688 

 0-435S 

 0.4061 

 0-3799 

 0.3565 



o.3355 

 0.3165 

 0.2994 

 0.2838 

 0.181 * 



* de Haas, 1894. Undercooled water: — 2.10 , 1.33 cp; —4.70°, 2.12 cp; 

 — 9.30 , 2.55 cp; White, Twining, J. Amer. Ch. Soc, 50, 380, 1913. 



-6.20 , 2.25 cp; — 8.48°, 2.46 cp; 



TABLE 171. — Viscosity of Alcohol-water Mixtures in Centipoises 

 (Temperature Variation) 



Smithsonian Tables. 



Same authority as preceding table. 



