Odor is a condition which, although less fre quent, is much more objectionable than turbidity or color. As a rule it is due to the life esses of minute organisms, and is to a considerable degree by filtration. It may, however, persist at certain times in the year and has been known to produce, or be followed by bowel disturbances among small children.
Sewage contamination is the most harmful of all the various forms of impurities natural or artificial that a water supply may be sub jected to, and is the direct cause of epidemics of typhoid fever and various troubles of the intestines, which by undermining the constitu tion reduces its power of resistance to other dis eases. The water may be somewhat purified by filtration, but the proper remedy is to remove the source of pollution. Failing this, even a much polluted water may be made reasonably safe for drinking by sterilization with chlorine.
The quality of water is ascertained by vari ous kinds of analyses, physical, chemical and bacteriological. Physical analyses consist merely of comparisons of the given samples with standard solutions, and afford data relative to temperature, turbidity, color and odor. Chem ical analyses indicate the time of past contami nation and the nature of its origin — animal or vegetable, and the content of mineral salts. Bacteriological analyses are principally used to ascertain the absence or presence of the growths which cause bad taste and odor. Such analyses are capable of showing the number and prob able origin of the bacteria present, but in mat Pets of differentiation, as in the case of the tvphoid germ from the harmless water bacteria, their operation is quite uncertain.
The results obtained by any set of analyses are generally interpreted by chemists and engi neers by comparing them with other known. fans, without attempting to establish a system of arbitrary standards. A minimum limit of impurity, however, may be stated, as follows: (1) The best authorities consider water as unfit for drinking purposes when 100,000 parts of the liquid contain more than three parts by aright of mineral matter or one part by weight of dry organic matter, before it has been sub mitted to precipitation, or when it holds in sus pension more than one part by weight of dry organic matter after six hours of perfect repose m a reservoir.
(2) When the same amount of liquid con tains in solution more than two parts by weight of organic carbon, or three parts of nitrates.
(3) If it exhibits a distinct color under day fight when placed in a white porcelain dish, to the depth of one inch.
(4) When 100,000 parts of the liquid con tain than two parts by weight of a salt of any metal except calcium, magnesium, potas mum and sodium.
(5) When 100,000 parts of the liquid contain in solution, suspension, or chemical combina tion. more than 0_5 part of arsenic.
(6) When 100,000 parts of the liquid, after the addition of sulphuric acid, contain more than one part by weight of free chlorine.
(7) 1APhen 100,000 parts contain more than me part by weight of sulphur in the form of salphuretted hydrogen, or a soluble sulphuret.
(8) When 100,000 pans of the liquid holds en suspension more than 03 part of petroleum of hydrocarbon, or exhibits a film of the same span its surface.
(9) When the acidity than that produced by two parts by weight of hydrochlo ric acid to 1.000 parts of distilled water.
(10) When the alkalinity is greater than that produced by adding one part by weight of mastic soda to 1,000 parts of distilled water.
(11) When 10 cubic centimeters of water contain more than 100 harmless bacteria. This is the requirement of the government for water served on railroad trains in interstate com merce, and is adopted by all bottlers of table waters.
Is general, a large percentage of chlorine and nitrates, together with the presence of Berthas cob coamemeis, an organism originating in large quantities in the human intestines, indi cate sewage contamination.
A very simple but reliable test for comansinatioe was suggested by a pint of the suspected water placed in a deaf cr4rirless glass-stoppered bottle, add a few mins of the best white lump-sugar, and expose the bottle freely to daylight in the window of a warns room for a week or 10 days. If the water remains clear it may be considered safe, Mt if it become turbid, it is open to grave sus POCIOD of sewage contamination.