-shaped shelves, placed at an angle of 45°, and riveted alternately to opposite sides of the vessel. This arrangement causes the water to take a serpentine course. The position of the shelves is indicated by the dotted lines.
As soon as the mixture of water and reagent flows down the pipe F, and enters the vessel E, the calcium carbonate commences to precipitate and settles upon the
-shaped shelves. At the top of the tank a layer of wood shavings, inclosed in wire-netting, is placed as shown by the dotted lines. This acts as a filter, and intercepts any particles that may not have subsided. The clear purified water passes away by the pipe I.
The precipitate that collects on the
-shaped plates is from time to time drawn off by the cocks shown at G; this may be done without interfering with the working of the apparatus. While there can be no doubt that the use of soft water is advantageous in the boiling, washing, and bleaching processes, and also of course for supplying steam boilers, it is probably an advantage to use a hard water for diluting the pulp before running it into the machine.
In the case of papers which are loaded with any of the forms of calcium sulphate (pearl-hardening, crystal-hardening, &c.) the use of very soft water is objectionable from the fact that a certain quantity of calcium sulphate is dissolved. This would not take place to the same extent with water which is already charged with sulphate and carbonate of calcium.
The removal of soluble iron from a water is effected by the softening processes described.
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