During the last two years a very considerable amount of work has been done at the Maine Laboratory of Hygiene upon the matter of formaldehyde disinfection. In the course of this work the formalinpermanganate method was first worked out as a means of practical disinfection. In one way this method seemed an anomaly, in that part of the agent which was to do the work of disinfection was itself used up in the reaction that furnished the heat to evaporate the formaldehyde solution. In looking for a means of surmounting this difficulty, the use of calcium carbide was suggested, and the subsequent work with this compound forms the basis of this paper. As is well known, when calcium carbide and water are mixed, there results a violent reaction from which acetylene gas is formed and driven off, while calcium oxide is theoretically the product remaining in the generator. In actual practice the residue in the generator is calcium hydroxide, resulting from the union of the first-formed oxide with water. The value of this reaction for disinfection does not lie