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.