lime, which, added in even so small an amount as 0 000426 gramme to a hundred cubic centimetres of water, kills all the micro-organisms within two hours. The bacteria appear to be acted upon much more promptly than the other organic matter present. For the removal of the excess of the agent the addition of sulphite of sodium (0 000209 gm.) suffices, and an excess of this substance up to 50 per ...