FROM THE PRACTICAL VIEWPOINT 



as it leaves the heater is then suddenly raised 

 5 to 10, and the time at which the rise takes 

 place is noted. A careful watch is then kept at the 

 outlet of the holder to determine when any rise in 

 temperature occurs at this point. The elapsed time 

 indicates the time of holding. The temperature, 

 instead of being raised, may be lowered a given 

 amount at the heater, and the corresponding drop 

 in temperature at the outlet noted. 



The inaccuracy of this method of testing is due 

 to the fact that during the long holding period 

 there is a natural tendency for the changed tem- 

 perature to become diffused throughout the sur- 

 rounding liquid. It can also be seen that when 

 the temperature is raised the natural tendency is 

 for the hotter liquid to remain on top of the tank, 

 while if the temperature is dropped, the tendency 

 is for the cooler liquid to settle toward the bot- 

 tom of the tank. A graphic chart can be made 

 showing the result of these tests very clearly. 

 Using the upright gradations of the chart to indi- 

 cate changes in temperature, and the horizontal 

 gradations to indicate periods of time, the sudden 

 rise at the heater will be clearly shown by an al- 

 most perpendicular line. The line showing the 



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