=Soap.=--Experimenters have obtained many conflicting results with soaps when tested on different organisms, as is to be expected from the great variations in this article. Miss Vera McCoy in the author’s laboratory carried out experiments with nine commercial soaps--Ivory, Naphtha, Packer’s Tar, Grandpa’s Tar, Balsam Peru, A. D. S. Carbolic, German Green, Dutch Cleanser, Sapolio--and obtained abundant growth from spores of _Bacillus anthracis_, from _Bacterium coli_ and from _Staphylococcus pyogenes aureus_ in all cases even when the organisms had been exposed twenty-four hours in 5 per cent. solutions. From these results and from the wide variations reported in the literature it is clear that _soap solutions alone cannot be depended on_ as disinfectants. Medicated soaps do not appear to offer any advantages in this respect. The amount of the disinfectant which goes into solution when the soap is dissolved is too small to have any effect. =Formaldehyde.=--Formaldehyde (HCHO) is perhaps the most largely used chemical disinfectant at the present time. The substance is a gas but occurs most commonly in commerce as a watery solution containing approximately 40 per cent. of the gas. This solution is variously known as formalin, formol, and formaldehyde solution. The first two names are patented and the substance under these names usually costs more. It is used in the gaseous form for disinfecting closed spaces of all kinds to the exclusion of most other means today. A great many types of formalin generators have been devised. The gas has little power of penetration and all material to be reached should be exposed as much as possible. The dry gas is almost ineffective, so that the objects must be moistened or vapor generated along with the gas. A common method in use is to avoid expensive generators by pouring the formaldehyde solution on permanganate of potash crystals placed in a vessel removed from inflammable objects on account of the heat developed which occasionally sets the gas on fire. The formalin is used in amounts varying from 20 to 32 ounces to 8-1/2 to 13 ounces of permanganate to each 1000 cubic feet of space. This method is expensive since one pint (16 ounces) of formalin is sufficient for each 1000 cubic feet, and since the permanganate is an added expense. Dr. Dixon, Commissioner of Health of Pennsylvania, recommends the following mixture to replace the permanganate, claiming that it works more rapidly and is less expensive and just as efficient: 1. Sodium bichromate, ten ounces. 2. Saturated solution of formaldehyde, sixteen ounces. 3. Common sulphuric acid, one and a half ounces. Two and three are mixed together and when cool are poured on the bichromate which is placed in an earthenware jar of a volume about ten times the quantity of fluid used. The quantities given are for each 1000 cubic feet of space.