The chemistry of plant and animal life . in filter. 64 AGRICULTURAL CHEMISTRY used for generating steam they produce a large amount ofboiler scale. This can be partially prevented by the useof materials containing tannic acid. 66. Methods of Improving Drinking Waters.—(i) By boiling, which destroys disease-producing organisms. Boiled or sterilized water, however, is not free from the poisonous compoundswhich many organismsproduce. In cases ofpestilential diseases,water should always beboiled. (2) By filteringthrough charcoal orthrough disks of un-glazed porcelain-likematerial, which resultsin
The chemistry of plant and animal life . in filter. 64 AGRICULTURAL CHEMISTRY used for generating steam they produce a large amount ofboiler scale. This can be partially prevented by the useof materials containing tannic acid. 66. Methods of Improving Drinking Waters.—(i) By boiling, which destroys disease-producing organisms. Boiled or sterilized water, however, is not free from the poisonous compoundswhich many organismsproduce. In cases ofpestilential diseases,water should always beboiled. (2) By filteringthrough charcoal orthrough disks of un-glazed porcelain-likematerial, which resultsin removing a large paitof the organic care, however,should be taken to keepthe filter clean, other-wise it will be a sourceof contamination. Boil-—: ing the water before fil- Fig. water filter. tcriug alsO imprOVCS itS sanitary condition. One of the most effectual forms ofwater filters is the Pasteur filter, in which the waterpasses through a series of tubes which present a large sur-face area for WATER 65 (3) By distilling, which removes all mineral impurities,and the water is also purified from organic matter. It isthe most effectual way of removing all kinds of impuritiesand rendering the water free from organisms, and safe foruse. CHAPTER IXAir 67. Air a flechanicai flixture.—Air is a mechanicalmixture composed of a number of gases and compoundsin about the following proportions : (i) nitrogen, 79 percent.; (2) oxygen, 20 per cent.; (3) carbon dioxid, cent.; (4) ammonium compounds in small amounts;(5) moisture; (6) ozone; (7) hydrogen peroxid; (8)argon ; (9) dust: organic matter, and air is a mechanical mixture is shown by its not hav-ing a constant chemical composition, which is necessaryfor all compounds, and when nitrogen and oxjgen aremixed, in the same proportion as in air, there is no evi-dence of a chemical reaction, as change of volume ortemperature. The air that is dissolved in water is ofdiffe
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