The Romance of Modern Chemistry

NATURAL WATERS different from pure water. Thus it is well known that practically all natural waters contain in solution an appreciable amount of solid matter. A large part of this solid matter may be deposited when the water is boiled, Fig. 2.—Showing the relative amounts of solid matter dis- solved in various waters. and a glance inside the kitchen kettle will, in many cases at least, suffice to show that this is the case. The so-called “ furring ” of a kettle is simply due to the solid matter depositing when the water boils. The same thing happens in engine boilers, and the incrustation or scale that forms on the plates of the boiler is a cause of serious trouble. For it is very diffi- cult to remove the scale with- out damaging the boiler, and so long as it is allowed to remain extra heat must be supplied to the boiler if the output of steam is to be main- tained. The extra heat is required because the scale is a bad conductor of heat, it has been found that a boiler incrustation one quarter of an inch in thickness involves a consumption of fuel 50 per cent, greater than would be required if the boiler plates were clean. Different natural waters contain quite different amounts of dissolved solid matter. Some, such as sea water, con- tain a great deal; others, such as rain water, contain very little. A good idea of the relative average amounts 98