§ Mr. H. Macmillan
In this country fluoride is not yet added to water supplies. In the United States of America, however, there is a growing practice to make such an addition and the fluoride is usually added as sodium fluoride, sodium silico-fluoride (fluosilicate) or hydrofluosilicic acid. The first two of these compounds are solid salts, but are usually made into an aqueous solution before adding to the water. Hydrofluosilicic acid is purchased as an aqueous solution.