36 



sire to experiment with deteriorated canes and untried cutting-machines, 

 the addition of the .calcium carbonate provides against disastrous re- 

 sults which would otherwise be inevitable. 



CLARIFYING OR DEFECATING THE JUICE. 



Immediately after it is drawn from the diffusion battery the juice is 

 taken from the measuring tanks into the defecating tanks or pans. These 

 are large, deep vessels, provided with copper steam coils in the bottom 

 for the purpose of heating the juice. Sufficient milk of lime is added 

 here to nearly or quite neutralize the acids in the juice, the test being 

 made with litmus paper. The juice is brought to the boiling point, and 

 as much of the scum is removed as can be taken quickly. The scum is 

 returned to the diffusion cells, and the juice is sent by a pump to the 

 top of the building, where it is boiled and thoroughly skimmed. These 

 skimmings are also returned to the diffusion cells. 



This method of disposing of the skimmings was suggested by Mr. 

 Parkinson. It is better than the old plan of throwing them away to 

 decompose and create a stench about the factory. Probably a better 

 method would be to pass these skimmings through some sort of filter, 

 or perhaps better still, to filter the juice and avoid all skimming. After 

 this last skimming the juice is ready to be boiled down to a thin sirup, 

 in 



THE DOUBLE-EFFECT EVAPORATORS. 



These consist of two large closed pans provided within with steam 

 pipes of copper, whereby the liquid is heated. They are also connected 

 with each other and with pumps in such a way as to reduce the press- 

 ure in the first to about three- fifths and in the second to about one- 

 fifth the normal atmospheric pressure. 



The juice boils rapidly in the first at somewhat below the temperature 

 of boiling water, and in the second at a still lower temperature. The 

 exhaust steam from the engines is used for heating the first pan, and 

 the vapor from the boiling juice in the first pan is hot enough to do all 

 the boiling in the second, and is taken into the copper pipes of the sec- 

 ond for this purpose. In this way the evaporation is effected without 

 so great expenditure of fuel as is necessary in open pans, or in single- 

 effect vacuum pans, and the deleterious influences of long continued 

 high temperature on the crystallizing powers of the sugar are avoided. 



From the double effects the sirup is stored in tanks ready to be taken 

 into the strike-pan, where the sugar is crystallized. 



THE FIRST CHANCE TO PAUSE. 



At this point the juice has just reached a condition in which it will 

 keep. From the moment the cane is cut in the fields until now every 

 delay is liable to entail loss of sugar by inversion. After the water is 

 put into the cells of the battery with the chips, the temperature is care- 



