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.
The chemical factory, Eisenbuettel, near Braunschweig, distributes the following circular: "The principal generators of incrustation in boilers are gypsum and the so-called bicarbonates of calcium and magnesium. If these can be taken put of the water, before it enters the boiler, the formation of incrustation is made impossible; all disturbances and troubles, derived from these incrustations, are done away with, and besides this, a considerable saving of fuel is possible, as clear iron will conduct heat quicker than that which is covered with incrustation."
J. Kolb, according to Dingler's Polyt. Journal, says: "A boiler with clear sides yielded with 1 kil. coal 7.5 kil. steam, after two months only 6.4 kil. steam, or a decrease of 17 per cent. At the same time the boiler had suffered by continual working."
Suppose a boiler free from inside crust would yield a saving of only 5 per cent. in fuel (and this figure is taken very low compared with practical experiments) it would be at the same time a saving of 3c. per cubic meter water. If the cleaning of one cubic meter water therefore costs less than 3c., this alone would be an advantage.
Already, for a long time, efforts have been made to find some means for this purpose, and we have reached good results with lime and chloride of barium, as well as with magnesia preparations. But these preparations have many disadvantages. Corrosion of the boiler-iron and muriatic acid gas have been detected. (Accounts of the Magdeburg Association for boiler management.)
Chloride of calcium, which is formed by using chloride of barium, increases the boiling point considerably, and diminishes the elasticity of steam; while the sulphate of soda, resulting from the use of carbonate of soda, is completely ineffectual against the boiler iron. It increases the boiling point of water less than all other salts, and diminishes likewise the elasticity of steam (Wullner).
In using magnesia preparation, the precipitation is only very slowly and incompletely effected--one part of the magnesia will be covered by the mire and the formed carbonate of magnesia in such a way, that it can no more dissolve in water and have any effect (Dingler's Polyt. Journal, 1877-78).
The use of carbonate of soda is also cheaper than all other above mentioned substances.
One milligramme equivalent sulphate of lime, in 1 liter, = 68 grammes sulphate of lime in 1 cubic meter, requiring for decomposition:
120 gr. (86-88 per cent.) chloride of barium of commerce--at $5.00 = 0.6c.
Or, 50 gr. magnesia preparation--at $10.00 = 0.5c.
Or, 55 gr. (96-98 per cent.) carbonate of soda--at $7.50 = 0.41c.
The proportions of cost by using chloride of barium, magnesia preparation, carbonate of soda, will be 6 : 5 : 4.