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_,