MANUFACTURE OF SALT FROM SEA-WATER 45 



of brick, tile, pottery, textiles, paper, soap, ice, oil, 

 leather, dyes, chlorine, soda, lye, sodium sulphate, 

 and practically all the sodium compounds with the 

 exception of sodium nitrate. It is also the source of 

 the chlorine of most of the chlorine compounds of 

 commerce, the most important of which are bleach- 

 ing powder, sodium h3rpochlorite, sodium chlorate, 

 sodium perchlorate, hydrochloric acid, and silver 

 chloride. Indeed its uses are so numerous and varied 

 that it is difficult to find an industry in which some 

 salt or product made from salt is not used. Conse- 

 quently the quantity of salt produced is much greater 

 than most people realize. In 1925, for example, the 

 United States alone produced 7,897,4)98 tons. Most 

 of this was low-priced salt used for industrial pur- 

 poses, the total value being only $26,162,361, or 

 less than four dollars a ton. 



Salt making is one of the most widely distributed 

 industries, some salt being prepared in almost every 

 country of the world. In addition to the United 

 States, China, Japan, India, Germany, England, 

 France, Portugal, Spain, Italy, Brazil, and many 

 other countries have important salt industries. In 

 some places salt is heavily taxed. In Italy, Aus- 

 tria, Turkey, and China, the salt industry is a 

 government monopoly. 



The important sources of salt are (1) mines, (2) 

 wells or springs, and (3) sea- water. Rock-salt is 

 obtained from mines in the salt deposits in the earth's 

 crust. Wells are usually operated by drilling into 

 salt deposits, pumping water down into the wells, 

 and simultaneously pumping up the saturated salt 



