The Romance of Modern Chemistry

NATURAL WATERS of solid matter contained in fresh waters from various sources will be obtained by a glance at the accompanying diagram. The heights of the columns are proportional to the amounts of solid matter in the various waters. Deep-well waters contain on the average about half an ounce of solid matter for every thousand ounces of water, and the proportion of solid matter in the other fresh waters may be roughly gauged from the diagram. If the amount of solid in sea water were to be represented in the same way, a column eighty times as high as the highest in the diagram would have to be introduced. This obviously must be left to the imagination of the reader. To the ordinary individual, waters are familiar as “ hard ” or “ soft,11 and this classification gives a rough idea of the amount of solid dissolved in the water. Hard waters contain a large amount of solid; soft waters, which require but little soap to make a lather, are those which are comparatively free from dissolved solid. The question next arises, what are the solids that we find in the various natural waters, and where do they come from ? If sea water is left out of account for the present, it may be said that the main substances occurring in natural waters are sulphate and carbonate of lime (and magnesia, to a less extent). The proportion of these substances held in solution by a water depends on its history. As a matter of fact, carbonate of lime (chalk) is not soluble in pure water, but only in water charged with carbon dioxide. If now the reader recollects that there is opportunity for rain to become charged with carbon dioxide from the atmosphere, he will understand that the water which falls on the surface of the earth and percolates through the soil and the rocks will have the power of 99