Of all salts found in the body, the most abundant and valuable is sodium chloride (NaCl), common salt; it exists in all tissues, secretions, and fluids of the body, with the exception of enamel of the teeth. The amount found in food is not always sufficient; therefore salt is used as a condiment. It assists digestion, inasmuch as it furnishes chlorine for hydrochloric acid found in gastric juice.
Common salt is obtained from evaporation of spring and sea water, also from mines. Our supply of salt obtained by evaporation comes chiefly from Michigan and New York; mined salt from Louisiana and Kansas.
Salt is a great preservative; advantage is taken of this in salting meat and fish.
Other salts—lime, phosphorus, magnesia, potash, sulphur, and iron—are probably obtained in sufficient quantity from food we eat and water we drink. In young children, perfect formation of bones and teeth depends upon phosphorus and lime taken into the system; these are found in milk, green vegetables, fruit, cereals, meat, and fish.
Starch is a white, glistening powder; it is largely distributed throughout the vegetable kingdom, being found most abundantly in cereals and potatoes. Being a force-producer and heat-giver it forms one of the most important foods. Alone it cannot sustain life, but must be taken in combination with foods which build and repair tissues.
Test for Starch. A weak solution of iodine added to cold cooked starch gives an intense blue color.
Starch is insoluble in cold water, and soluble to but a small extent in boiling water. Cold water separates starch-grains, boiling water causes them to swell and burst, thus forming a paste.
Starch subjected to dry heat is changed to dextrine (C6H10O5), British gum. Dextrine subjected to heat plus an
