20 



PHYSICS OF STREAMING 



SECTION 8. Influence of Temperature on Viscosity. 



With very few exceptions the viscosity of a solution decreases as the" 

 temperature rises, and each substance has its own specific rate of decrease. 

 The influence of temperature on the viscosity of albumin was investigated 

 by means of the apparatus shown in Fig. 3. The flask A contains either 

 brine cooled by a freezing-mixture, or water heated to any required 

 temperature. This can be siphoned to and fro through the water-jacket B 

 by means of an adjustable reservoir (as at F) attached to D. By lowering the 

 mercury reservoir F, albumin from K is drawn up to the mark C,and the clip 

 N closed. The mercury in F is then raised, and when it has ceased to 

 flow into E, and the temperature in B is constant, the clip N is opened, 

 and the time the albumin takes to fall to the mark H is noted. The volume 

 CH is very much less than that of E or F, and hence the pressure is 

 practically uniform throughout, while since the velocity is low and the 

 differences of velocity small, the viscosities are directly proportional to 

 the times of flow. 



The apparatus was first tested by calculating the viscosities of sugar 

 solutions and of dilute glycerine of known strength at different tempera- 

 tures from their relative times of flow and the values for one of them 

 given in Landolt and Bornstein's * Tabellen.' A series of experiments 

 were then made with egg-albumin, prepared as previously described, 

 each of the figures given being the average of three experiments. 



The viscosity of egg-albumin containing 10-8 per cent, of solids steadily 

 decreases up to 60 C., although the decrease becomes less and less per 

 degree as the temperature rises. Above 60 C. the viscosity increases, 

 and at 65 C. it is greater than at 3 C., while at 70 C. the coagulation 

 stops all flow. Hence a rise of temperature within certain limits will 

 directly accelerate streaming independently of any increased energy of 

 respiration, and that to no small extent since a rise of temperature from o C. 



The rapid rate of flow is necessary owing to the difficulty of maintaining the temperature 

 absolutely constant for any length of time. 



