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8. If the water in the well is bad, more permanganate will be necessary. In such a case it will be found that the strong red colour at first produced quickly changes to brown, and then fades away. This is because the permanganate destroys dirt and is destroyed by it. Therefore, if the water in the well is clean, a smaller quantity of permanganate will be necessary. From one to four ounces of permanganate will be found to be enough for ordinary wells. If more permanganate is added than is enough to produce a faint permanent red colour, it is likely that frogs, that may be in the well, will be killed. This will, in a few days, give the water a putrid taste. If the quantity of permanganate is not enough to produce a faint permanent red colour, it is unlikely to do good. If possible, the permanganate should be added at night, in order to leave the wells undisturbed as long as possible. The water will be fit to drink on the following morning. If then a red colour is still present, the water may have an unpleasant taste, but it is perfectly harmless.