Having obtained the results of the several tests, it remains to interpret them. If the water examined is found to lose color rapidly under the permanganate test - to contain an undue amount of chloride - and also free ammonia, it must be pronounced hopelessly bad, and, in most cases, the source of supply had better be abandoned. If, on the other hand, the color changes but slowly, the amount of chlorides is but little more than 5 in 100,000, and no free ammonia, or only a very slight trace, is discovered, the effect of cleaning out the well, and a careful protection of the surroundings, may be tried, after which another test should be made. If the color remains a good pink for 24 hours, only a small amount of chlorides is present, and no ammonia, the water may be pronounced good.

At the same time it must be remembered that no chemical tests can make it quite certain that a drinking water is entirely free from disease germs.

Nearly enough has been said, under the several divisions, to direct one to fair conclusions. It must not be inferred that the methods presented here are infallible guides to the quality of a water. All that can be claimed for them is, that in most cases they will reveal the character of waters which are so polluted as to be immediately injurious to health. Some that are polluted with vegetable matter alone may escape detection. Other tests, which cannot be used by people generally, must be made before all that can be known of a water will be revealed.

It is seldom that a bad water will show all the indications that have been described. If an excess of both chlorine and ammonia occurs, the water is polluted with animal matter or with drains. If considerable chlorine is present, together with a strong reaction for nitrates or nitrites, while ammonia is not found by means of the test described, a past or future pollution is indicated. If an excess of ammonia alone occurs, contamination from vegetable matter is suggested, which becomes quite certain if the sugar test and the permanganate of potash have given a reaction.

But there are more conditions and variations than can be specified for every case. The application of the tests, and an examination of the surroundings of a well, together with thought and judgment, will usually lead to the right conclusion.

A good natural water for manufacturing carbonated beverages should be free from organic impurities as near as can be, for very few waters, in a natural condition, are absolutely pure in this respect; it should not contain more than twenty or thirty grains of solid matter per gallon, and if it contains over this, it should be capable of being removed by a soften-ing process. It should not contain much air, and the quantity of chlorine per gallon must not exceed one to two grains for ordinary water, although this quantity is considerably exceeded by deep well-water. A little experience is required in order to decide on the merits of a water from the results of analysis. An impure water would unhesitatingly be condemned, but a very pure water may involve us in trouble almost as serious; so that, without going into this part of the subject fully, it would be impossible to give much information which would be generally applicable.

As may readily be perceived, the above methods are valuable only for a superficial qualitative investigation. If an exact qualitative or quantitative analysis of the nature of the water is required, it is best to send a liberal sample to a professional chemist.