760 MAN'S PHYSICAL WELFARE Detergents and Abrasives Have Their Place in Cleanliness as Well as in Industry. Abrasives are useful in removing films of foreign material by mechanical action. Many abrasives of different degrees of hardness are available, and it is important to select the proper abrasive for a given purpose. Powdered glass, though a good abrasive, will soon wear the enamel from the teeth when used as a constituent of a dentifrice. Certain popular abrasives that contain volcanic ash or diatomaceous earth and similar powders are frequently too coarse for continued use on enamel or porcelain. Detergents are substances that have cleansing qualities similar to those of soaps. Sodium alkyl sulfates, such as sodium lauryl sulfate, and triethanolamine lauryl sulfate have been patented and are licensed for sale for special purposes under such names as "Drene," "Dreft," "Teel," and "Irium." They have the detergent properties of soap, but they do not form alkaline solutions and are unaffected by hardness in waters. In addition to the sodium alkyl sulfates which have been made available for domestic uses, there are fifty or more other types of "soapless soaps" which are finding wide application, especially in the textile industries. Phosphates Are Rapidly Finding Favor in American Homes. The known phosphate rock deposits in the United States amount to about seven billion tons. Of that amount about 9 per cent are located in Florida and Tennessee, where phosphorus is being extracted from phosphate rocks by electrochemical methods at Muscle Shoals Dam by the T.V.A. Nearly 91 per cent of the phosphate deposits are located in the western states, Idaho, Montana, Utah, and Wyoming. These western deposits are being utilized to a small extent only, partly because of the high cost of transportation, but largely because the underground mining methods required to work these deposits are more expensive than the surface mining methods used in Florida and Tennessee. The most important use of phosphates is in fertilizers, but three sodium phosphates are coming into wide use in industry and in the homes of the United States. 1. Trisodium Phosphate. • Trisodium phosphate, Na3P04 I2H2O, hydrolyzes to produce a solution which is more strongly basic than soap but not as strongly basic as lye. This salt is the cheapest of the sodium phosphates and is used for cleaning operations such as washing dishes or cleaning sinks and tubs, where a moderately strong alkali will do no harm.
NATURALLY OCCURRING SOLUBLE SALTS 761 2. Sodium Pyrophosphate. This salt, Na4P207, is often used as a substitute for sodium hexametaphosphate because it is cheaper. It hydrolyzes to produce a mildly alkaline solution and may be used in washing even the most delicate fabrics such as silks and woolens. Sodium pyrophosphate is used with soap because it not only acts as an excellent detergent but it also prevents the formation of insoluble soaps, thus softening hard water. Several commercial soap powders contain this salt. It is used for dispersing clay in such applications as treatment of oil-well mud, in dairy cleaning because of its excellent emulsifying action on casein and butter fat, in cleaning textiles, and in the preparation of stable asphalt emulsions. 3. Sodium Hexametaphosphate. Sodium hexametaphosphate, (NaP03)6, is a patented chemical which is licensed for sale for a wide variety of specialized uses under different names. Under the name of "Calgon," sodium hexametaphosphate is sold for washing operations. It represents one of the few major contributions to the science of washing. Its rapid and widespread acceptance by laundries, restaurants, and critical housewives, despite its relatively high price, is based on the fact that it combines with calcium and magnesium ions to form complex ions that will not precipitate with soluble soaps. "Calgon" will also dissolve insoluble soap precipitates. It is much more efficient than sodium pyrophosphate as a water-softener. For the average hard water, less than a tablespoonful of "Calgon" per gallon is required. It is especially useful as a bath salt and as a hair rinse. Sodium hexametaphosphate will find wide application in many other fields of usefulness as its interesting properties come to be better known; for example, it is used in the treatment of burns because of its tanning action on albuminous materials. It has a strong healing action on such skin irritations as poison oak, poison ivy, sunburn, and athlete's foot. Sodium hexametaphosphate in concentrations of 0.5 to 5 parts per million has a marked inhibitive action on the corrosion of iron and steel by water. Sodium hexametaphosphate is also used in the treatment of boiler waters to prevent the formation of boiler scale, in photography, in pharmaceutical and cosmetic preparations such as toothpaste, and in insecticide sprays. The Development of the Borax Industry Is a Story Worth Telling. When borax was first discovered in some of the salt flats of the deserts of California and Nevada, its high price made it very much worth while to work small deposits; but these deposits were soon exhausted. Then borax was discovered in Death Valley, where it was obtained by leaching it out of the salt deposits scraped up from the