WHAT IS DIFFUSION?

The condition in which the sugars and other soluble substances exist in the cane is that of solution in water.  The sweetish liquid is contained, like the juices of plants generally, in cells.  The walls of these cells are porous.  It has long been known that if a solution of sugar in water be placed in a porous or membraneous sack, and the sack placed on water, an action called osmosis, whereby the water from the outside and the sugar solution from the inside of the sack each pass through, until the liquids on the two sides of the membrane are equally sweet.  Other substances soluble in water behave similarly, but sugar and other readily crystallizable substances pass through much more readily than uncrystallizable or difficultly crystallizable.  To apply this properly to the extraction of sugar, the cane is first cut into fine chips, as already described, and put into the diffusion cells, where water is applied and the sugar is displaced.

[Illustration:  Fig. 1—­APPARATUS FOR MANUFACTURE OF SORGHUM BY THE DIFFUSION PROCESS.]

THE DIFFUSION BATTERY,

as used at the Parkinson factory, consists of twelve iron tanks. (See diagram.) They are arranged in a line, as shown in diagram, Fig. 1.  Each has a capacity of seventy-five cubic feet, and by a little packing holds a ton of cane chips.  The cells are supported by brackets near the middle, which rest on iron joists.  Each cell is provided with a heater, through which the liquid is passed in the operation of the battery.  The cells are so connected by pipes and valves that the liquid can be passed into the cells, and from cell to cell, at the pleasure of the operator.  The bottom of each cell consists of a door, which closes on an annular rubber hose placed in a groove, and filled with water, under a pressure greater than that ever given to the liquids in the cell.  This makes a water tight joint whenever the trap door bottom is drawn up firmly against it.  The upper part is of cast iron and is jug shaped, and is covered with a lid which is held with a screw on rubber packing.  In the jug neck and near the bottom the sides are double, the inner plates being perforated with small holes to let water in and out.  The bottoms are double, the inner plates being perforated like the neighboring sides, and for the same purpose.  The cells, of whose appearance a fair idea may be had from diagram, Fig. 2, are connected with a water pipe, a juice pipe, a compressed air pipe, and the heaters, by suitable valves.  The heaters are connected with a steam pipe.  This, and the compressed air pipe, are not shown in the diagram.  The water pipe is fed from an elevated tank, which gives a pressure of twelve pounds per square inch The valve connections enable the operator to pass water into the cells at either the top or the bottom; to pass the liquid from any cell to the next, or to the juice pipe through the heater; to separate any cell from any or all others, and to turn in compressed air.