194 TiMEHRI. 



ing proportion of volatile acids met with in cane juice. It may be laid 

 down that the proportion of acid — phosphoric or other — required to be 

 added to the juice in the eliminators to produce the suitable yellow 

 tint, is a measure of the volatile acids present in a state of combination 

 in the original juice, and in proportion to this so will there be corrosion 

 of the calandria tubes. 



While on this subjeft I may point out that the scaling of the inner 

 surface of the tubes from the use of phosphorus acid is due to the 

 phosphate of lime becoming insoluble at the moment when its solvent 

 acid is boiled off; and that such scaling is more manifest in some 

 evaporators than in others, is simply due to the difference in the 

 proportion of volatile acid in the original juice dealt with. 



As to the ammonia, from the presence of which and its adiather> 

 mancy, Mr. Abell argues a retardation of condensation, with consequent 

 effeft on the temperature of the previous body, this in the manufa6lure 

 of cane sugar, as commonly carried out, does not occur. In beet 

 manufafture, with its processes involving excessive liming for the 

 purpose of destroying albuminous matter, ammonia is produced from 

 the nitrogen of the latter. But with cane juice treatment it is different. 

 In fact, it is the absence of glucose in beet juice which renders the 

 employment of large quantities of lime feasible, and conversely its 

 presence in cane juice which precludes the mode of treatment, from the 

 discolouration produced by the aftion of the alkali and the glucose. 



As to the influence of bodies of uncondensed or uncondensible gases 

 moving about the upper part of the calandria and thus veiling some of 

 the heating surface from contact with the vapour proper, I do not 

 consider that notable effeft is thereby produced on the temperature of 

 the vessels. I have not found that Multiple Effects fitted with gas 

 (falsely by us termed " ammonia ") connexions with main pump have 

 exhibited any difference in relation of temperature when compared with 

 machines working without these connections. 



Mr. Abell has done good service in laying down the necessary provi* 

 sions for experiments with evaporators, and I trust that now the subjeft 

 has been ventilated, experimental results from independent sources will 

 follow. 



In the matter of Prof. Harrison's " Standard method of 

 Polarisation," the writer asked that it might be withdrawn, 

 as so little interest seemed to have been taken in it. 



