The cutters are started, and cell 1 is filled with chips. This done, the chips from the cutters are turned into cell 2; cell 1 is closed, and cut off from the others, and water is turned into it by opening valve, c, of cell 1 (see Fig. 2) until it is filled with water among the chips. When 2 is filled with chips, its valve, a, is raised to allow the liquid to pass down into the juice pipe. Valve a of 3 is also raised. Now the juice pipe fills, and when it is full the liquid flows through valve, a, of 3, and into the heater between 2 and 3, and into the bottom of 2, until 2 is full of water among the chips. (This may be understood by following the course of the arrows shown in the diagrams of 9 and 10). Valve a of 2 is now screwed down; c is down and b is opened. It will be readily seen by attention to the diagram that this changes the course of the flow so that it will no longer enter at the bottom, but at the top of 2, as shown by the arrows at cell 2.
It is to be observed that the water is continually pressing in at the top of 1, and driving the liquid forward whenever a valve is opened to admit it to another cell, heater, or pipe. When cell 3 is full of chips, its valves are manipulated just as were those of 2. So as each succeeding cell is filled, the manipulation of valves is repeated until cell 6 is filled with liquid. After passing through six cells of fresh chips, this liquid is very sweet, and is drawn off into the measuring tank shown at p in diagram, Fig. 1, and is thence conveyed for subsequent treatment in the factory. To draw this juice from 6, valve a of 7 is raised to connect the heater between 6 and 7 with the juice pipe. A gate valve in the juice pipe is opened into the measuring tank, and the pressure of water into the top of 1 drives the liquid forward through the bottom of 1, through the heater, into the top of 2, out from the bottom of 2, through the heater into the top of 3, out from the bottom of 3, through the heater into the top of 4, out from the bottom of 4, through the heater, into the top of 5, out from the bottom of 5, through the heater, into the top of 6, and now out from the bottom of 6, through the heater, into the juice pipe, and from the juice pipe into the measuring tank. It will be understood that the liquid which is drawn from 6 is chiefly that which was passed into 1 when it was filled with chips. There is doubtless a little mixing as the pressure drives the liquid forward. But the lighter liquid is always pressed in at the top of the cells, so that the mixing is the least possible. The amount of liquid, now called juice, which is drawn from 6 is 1,110 liters, or 291 gallons. When this quantity has been drawn into the measuring tank, the gate valve is closed, and the valves connecting with 7 are manipulated as were those of 6, a measure of juice being drawn in the same way. All this time the water has been passed into the top of 1, and this is continued until the juice has been drawn from 9. Valve c to cell 1 is now closed, and compressed air is turned into the top of 1 to drive the liquid forward into 10. After the water has thus been nearly all expelled from 1, valve a of cell 2 is lowered so as to shut off communication with the juice pipe, and b, of cell 2 is closed. a and b of cell 1 have, it will be observed, been closed or down from the beginning. Cell 1 is now isolated from all others. Its chips have been exhausted of sugar, and are ready to be thrown out. The bottom of 1 is opened, and the chips fall out into the car, o (see diagram, Fig. 1), and are conveyed away. Immediately on closing valves a and b of cell 2, c is opened, and the water presses into the top of 2, as before into the top of 1, and the circulation is precisely similar to that already described, 2 having taken the place of 1, 3 of 2, and so on.
When 2 is emptied, 3 takes the first place in the series and so on. When 12 has been filled, it takes the l3th place. (The juice pipe returns from the termination of the series, and connects with 1, making the circuit complete.) The process is continuous, and the best and most economical results are obtained if there is no intermission.
One cell should be filled and another emptied every eight minutes, so that in twenty-four hours the number of cells diffused should be one hundred and eighty.
WHAT HAS TAKEN PLACE IN THE DIFFUSION CELLS.
For the purpose of illustration, let us assume that when it has been filled with chips just as much water is passed into the cell as there was juice in the chips. The process of osmosis or diffusion sets in, and in a few minutes there is as much sugar in the liquid outside of the cane cells as in the juice in these cane cells; i.e., the water and the juice have divided the sugar between them, each taking half.
Again, assume that as much liquid can be drawn from 1 as there was water added. It is plain that if the osmotic action is complete, the liquid drawn off will be half as sweet as cane juice. It has now reached fresh chips in 2, and again equalization takes place. Half of the sugar from 1 was brought into 2, so that it now contains one and a half portions of sugar, dissolved in two portions of liquid, or the liquid has risen to three quarters of the strength of cane juice. This liquid having three fourths strength passes to 3, and we have in 3 one and three fourths portions of liquid, or after the action has taken place the liquid in 3 is seven eighths strength. One portion of this liquid passes to 4, and we have one and seven eighths portions of sugar in two portions of liquid, or the liquid becomes 15/16 strength. One portion of this liquid passes to 5, and we have in 5 one and fifteen sixteenths portions of sugar in two portions of liquid, or the liquid is 31/32 strength. It is now called juice. From this time forward a cell is emptied for every one filled.
Throughout the operation, the temperature is kept as near the boiling point as can be done conveniently without danger of filling some of the cells with steam. Diffusion takes place more rapidly at high than at low temperatures, and the danger of fermentation, with the consequent loss of sugar, is avoided.