" Multiple Evaporation." 



ammoniacal compounds, and that ammonia is adiather- 

 manous whilst steam is diathermanous. Is it not rational 

 to conclude that these gases, separated from the steam 

 and collefted in blocks, and also the remainder partly 

 mixed with steam may bring about a totally different 

 effe6l to what would be obtained from pure steam ? A 

 trial of the condition and behaviour of an evaporator 

 dealing with water would let much light on the point. 



In paragraph (d) we have an apparent anomaly very 

 difficult to account for, particularly when we consider 

 that ammoniacal gases boil at two-thirds of the tempera- 

 ture required to boil water. This particularly calls for 

 our consideration, for in the writer's limited experience 

 it appears rational to conclude that the light gases should 

 be given off in the eliminators, particularly on estates 

 where yellow sugar is made, and the juice retained a 

 considerable time under the boiling a6lion of high pres- 

 sure steam. Again, if not all liberated in the eliminator, 

 one would expe6l to find the lighter gases given off in 

 the first vessel of the multiple evaporator. Such is not 

 the case. We all know that it is in the second vessel, 

 at a temperature of i8o° F., and a vacuum of 15" that 

 these light gases are most a6lively given off, and passing 

 over to the third vessel distin6lly separate and appro- 

 priate spots and blocks to themselves, mostly at the top, 

 and usually at the side remote from the entrance of the 

 vapour to that calandria. It is the wandering about of 

 these blotches or blocks of ammoniacal or similar gases 

 that doubtless accounts for the wandering irregular flow 

 of circulation or boil in the second vessel ; and the spas- 

 modic constantly changing position of flow in the third 

 vessel as instanced by Mr. Cornish, 



B 



