Water is usually classified as surface and ground water. Rain water and water from streams and rivers belong to the first class. Well water and deep spring water belong to the second. Rain water is our purest water, if it is col- lected from a clean surface after the dust in the air has been washed out. This water, flowing along the ground or through it, dissolves or carries along with it many different substances. Water which has much mineral substance dissolved in it is called hard ; this is the water that will not lather easily with soap. Hard water is, however, of two kinds. In one case there is present a soluble lime salt which precipitates if the water is boiled. This is the water which leaves a crust on the inside of a tea kettle. It is called temporarily hard because the water itself is softer after the boiling. Water containing salts of lime and magnesium which are unaffected by the boiling is called permanently hard. Permanently hard water may, however, be softened by the addition of such chemicals as soda, ammonia, and borax. Soft water is much the best for washing and also for cooking, but it is not so palatable as harder water. Water that is very hard is possibly not WATER 45 so good for us. If it can be softened by boiling, it may be cooled and used for drinking. Water is a carrier of bacteria, and the most harmful water is not hard water, but water which contains harm- ful bacteria. There are many kinds of domestic filters which are supposed to remove the bacteria from the water. Most of them are not reliable and, in any event, need great care. They must be sterilized frequently or the water which goes through them will be found to con- tain more bacteria than it did before. If there is any reason to believe that the water is dangerous, it is much safer to sterilize the water by boiling it. All that is necessary is to bring the water to boiling and then cool it. Water which has been boiled tastes flat because it contains less air dissolved in it. The palatability can be increased by pouring the water back and forth from one pitcher to another so as again to dissolve air in it. Freezing does not sterilize water. While in cities, at least, our water usually comes from a reservoir that is carefully protected from contamination, our ice supply may come from a private pond in which the water may be quite impure. Unless it is known that the water from which the ice was made was pure, the ice itself should not be put into beverages or foods. Instead, they can be set on ice to cool. So-called artificial ice is manufactured by freezing water in large tanks, the necessary cold tem- perature being often obtained by the evaporation of ammonia. Such ice is as pure as the water from which it is made. REFERENCES U. S. Dept. of Agriculture. Bulletin 57. "Water Supply, Plumb- ing and Sewage Disposal for Country Houses." OGDEN. "Rural Hygiene." 46 FOOD STUDY QUESTIONS 1. What diseases are most frequently carried by water? 2. Why is the water from shallow wells often dangerous ? 3. How should such wells be protected ? 4. Why is deep well water usually safer ? 5. How is the question of sewage disposal bound up with the question of a safe water supply ? VIII USE OF WATER IN COOKING POACHED EGGS A. Class Experiment. SOLUBILITY OF EGG WHITE.

AI-modernized reading of the original text

Water is usually classified as surface and ground water. Rain water and water from streams and rivers belong to the first class. Well water and deep spring water belong to the second. Rain water is our purest water, if it is collected from a clean surface after the dust in the air has been washed out. This water, flowing along the ground or through it, dissolves or carries along with it many different substances. Water which has much mineral substance dissolved in it is called hard ; this is the water that will not lather easily with soap. Hard water is, however, of two kinds. In one case there is present a soluble lime salt which precipitates if the water is boiled. This is the water which leaves a crust on the inside of a tea kettle. It is called temporarily hard because the water itself is softer after the boiling. Water containing salts of lime and magnesium which are unaffected by the boiling is called permanently hard. Permanently hard water may, however, be softened by the addition of such chemicals as soda, ammonia, and borax. Soft water is much the best for washing and also for cooking, but it is not so palatable as harder water. Water that is very hard is possibly not so good for us. If it can be softened by boiling, it may be cooled and used for drinking. Water is a carrier of bacteria, and the most harmful water is not hard water, but water which contains harmful bacteria. There are many kinds of domestic filters which are supposed to remove the bacteria from the water. Most of them are not reliable and, in any event, need great care. They must be sterilized frequently or the water which goes through them will be found to contain more bacteria than it did before. If there is any reason to believe that the water is dangerous, it is much safer to sterilize the water by boiling it. All that is necessary is to bring the water to boiling and then cool it. Water which has been boiled tastes flat because it contains less air dissolved in it. The palatability can be increased by pouring the water back and forth from one pitcher to another so as again to dissolve air in it. Freezing does not sterilize water. While in cities, at least, our water usually comes from a reservoir that is carefully protected from contamination, our ice supply may come from a private pond in which the water may be quite impure. Unless it is known that the water from which the ice was made was pure, the ice itself should not be put into beverages or foods. Instead, they can be set on ice to cool. So-called artificial ice is manufactured by freezing water in large tanks, the necessary cold temperature being often obtained by the evaporation of ammonia. Such ice is as pure as the water from which it is made. U. S. Dept. of Agriculture. Bulletin 57. "Water Supply, Plumbing and Sewage Disposal for Country Houses." OGDEN. "Rural Hygiene." 1. What diseases are most frequently carried by water? 2. Why is the water from shallow wells often dangerous ? 3. How should such wells be protected ? 4. Why is deep well water usually safer ? 5. How is the question of sewage disposal bound up with the question of a safe water supply ? POACHED EGGS A. Class Experiment. SOLUBILITY OF EGG WHITE.

Food study