180 ANNUAL REPORT 



the most valuable agent for conveying heat to this liquid to be 

 evaporated, as its use implies security against damage by reason 

 of overheating or burning. 



The temperature of steam can no more be higher than that 

 due to the pressure per square inch, than the stream can rise 

 higher than the fountain; hence the complete protection from all 

 liability to damage or deterioration due to a high, irregular and 

 aggressive heat. Even should the steam pressure be carried as 

 high as 120 pounds to the square inch, the temperature would 

 not exceed 340° and the persistent or effective temi^erature in 

 the shallow body of liquid being evaporated, would vary but 

 little from that found with a pressure of 70°. With the latter 

 pressure the temperature of the liquid in which the steam coil 

 or pipe is submerged will not, under the ordinary conditions of 

 evaporation, vary much from 215° to 220°. 



This relatively low temperature is, however, directly depen- 

 dent upon maintaining a shallow body of the liquid being evap- 

 orated. The depth of this incumbent upon the steam pipe or 

 coil acts as an obstruction to the free and liberal escape upward 

 of the bubbles of steam formed at the coil, and should it be al- 

 lowed to increase there will be a corresponding increase of the 

 resistance and a like increase of the temperature until the latter 

 is nearly if not quite equal to that of the steam within the coil. 

 Thus the liquid being evaporated is the chief condition which 

 determines and regulates this temperature, and it is easily seen 

 that to keep within the lowest range of temperature the depth 

 of the liquid must be kept at the lowest practicable, and main- 

 tained at that depth with all the accuracy possible. 



In evaporating a deep body of cane juice by means of heat ra- 

 diated from a steam pipe or coil in the bottom-of the vessel there 

 is a reckless waste of fuel and time and a wanton destruction or 

 breaking down of the most valued properties of the juice. The 

 chemical and mechanical factors involved are the same, whether 

 the liquid be in deep or shallow body; these are heat, pressure, 

 time and space. 



If in shallow body, these factors develop almost instantaneously 

 the phenomena of bubbles of expanding steam escaping from the 

 coil without resistance, and consequently at the lowest range of 

 temperature, and, by reason of their expansion constantly di- 

 minishing in temperature. If in deep body, the incipient bubble 

 of steam remains attached to the coil until all the factors of the 

 phenomena are reinforced sufficiently to enable it to detach from 



