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CHAPTER XVIII 



that Ci - Ji < C.^ — J2 < C.3 — J:i < C^ — J^, but very often C^ ~ J.^ 

 is found to be less than C^ — J^, and infrequently C3 — J^ is also less than 

 Ci — /i- The excessive absorption in the last body is accounted for by 

 the lower temperature at which it boils, by the greater quantity of scale 

 depositing on the tubes, by the viscosity and consequent lower rate of 

 transmission in the heavy syrup, and also by the lower density of the steam. 

 The lower rate frequently observed in the first body is probably to be ac- 

 counted for by a deposit of oil and grease on the steam side of the tubes 

 and also in some cases to scale on the juice side, particularly if badly defecated 

 juices are sent to the evaporator. Another cause is to be found in the heating 

 required in this cell. An entirely different factor controlling the distribution 

 of the fall lies in the manipulation of the valves controlling the incondensible 

 gas system. 



Below are given some actual observations by the writer ; as for the 

 apparatus, i, 2, 3 were of the vertical submerged tube type, 4 was a hori- 

 zontal submerged tube, and 5 was a horizontal film apparatus. 



A very detailed series of observations of this nature has also been made 

 by Kerr^" covering in addition double and triple effects. The same relatively 

 great absorption was observed in the last body, amounting to from 39 to 63 

 per cent, of the total in quadruples, from 50 to 68 per cent, in triples, and 

 from 49 per cent, to 84 per cent, in double effects. Similarly, his results 

 also show a very irregular distribution of the fall as between the first three 

 or first two bodies. 



Temperatures and Pressures. — The temperatures and pressures observed 

 do not correspond with those for saturated steam, and invariably some degree 

 of superheat is found. In a vertical submerged tube apparatus the following 

 observations were made : — 



