This section is from "Scientific American Supplement Volumes 275, 286, 288, 299, 303, 312, 315, 324, 344 and 358". Also available from Amazon: Scientific American Reference Book.
If we use for ten cubic meters water, one kilogramme lime, or in one day (in twenty-four hours), 240 cubic meters 24 kg. lime, a vessel four or five feet high and about 700 liters capacity, in which daily 24 kg. lime with about 100 liters water are slaked and then diluted to the mark 600, constantly stirring, 25 liters of this mixture contain exactly 1 kg. slaked lime.
Before using, this milk of lime has to be stirred up and allowed to settle for a few seconds; and then we draw off the required quantity of milk of lime (in our case 25 liters) through a faucet about 8 inches above the bottom, or we can dip it off with a pail. For the first precipitate we always need the exact amount of milk of lime, which we have figured out, or rather some more, but for the next precipitates we do not want the whole quantity, but always less, as that part of the lime, which does not settle with the precipitate, will be good for use in further precipitations. It is therefore important to control the addition of milk of lime by the use of litmus paper. If we do not add enough lime, it prevents the formation of the flocky precipitate, and, besides, more carbonate of soda is used. By adding too much lime, we also use more carbonate of soda in order to precipitate the excess of lime. We can therefore add so much lime, that there is only a very small excess of hydrous lime in the water, and that after well stirring, a red litmus paper being placed in the water for twenty seconds, appears only slightly blue. After a short time of practice, an attentive person can always get the exact amount of lime which ought to be added. On adding the milk of lime, we have to dissolve the required amount of pure carbonate of soda in an iron kettle, in about six or eight parts hot water with the assistance of steam; add this to the other liquid in the precipitating reservoirs and stir up well. The water will get clear after twenty-five or thirty minutes, and is then drawn off into the pure water reservoir.
In order to be convinced that the purification of the water has been properly conducted, we try the water in the following manner. Take a sample of the purified water into a small tumbler, and add a few drops of a solution of oxalate of ammonia; this addition must neither immediately nor after some minutes cause a milky appearance of the water, but remain bright and clear. A white precipitate would indicate that not enough carbonate of soda had been added. A new sample is taken of the purified water and a solution of chloride of calcium added; a milky appearance, especially after heating, would show that too much carbonate of soda had been added.
1. The boilers do not need to be cleaned during a whole season, as they remain entirely free from incrustation; it is only required to avoid a collection of soluble salts in the boiler, and therefore it is partly drawn off twice a week.
2. The iron is not touched by this purified water. The water does not froth and does not stop up valves. The fillings in the joints of pipes, etc., do not suffer so much, and therefore keep longer.
3. The steam is entirely free from sour gases.
4. The production of steam is easier and better.
5. A considerable saving of fuel can soon be perceived.
6. The cost of cleaning boilers from incrustation, and loss of time caused by cleaning, is entirely done with. Old incrustations, which could not be cleaned out before, get decomposed and break off in soft pieces.
7. The cost of this purification is covered sufficiently by the above advantages, and besides this, the method is cheaper and surer than any other.
The chemical factory, Eisenbuettel, furnishes pure carbonate of soda in single packages, which exactly correspond with the quantity, stated by the analysis, of ten cubic meters of a certain water. The determination of the quantities of lime and carbonate of soda necessary for a certain kind of water, after sending in a sample, will be done without extra charge.--Neue Zeitung fur Ruebenzucker Industrie.