DISINFECTION AND DISINFECTANTS 255 



temperature, sealing of the room, the use of at least GO 

 grammes of formaldehyde per 1,000 cubic feet (preferably 

 more, up to 120 grammes), and, in the case of large 

 rooms, mixture of the gas with the air of the room, either 

 mechanically or by the provision of a multiplicity of inlets 

 for the gas into the atmosphere. In the Alformant lamp 

 twenty-five tablets of paraform are volatilised for every 

 100 square feet of floor space. The Kuhn lamp generates 

 formaldehyde by the partial oxidation of methyl alcohol. 

 In the Trenner-Lee retort and Lingner apparatus form- 

 aldehyde gas and water vapour are passed into the 

 room. The ' Maine process ' requires only a 10-quart 

 tin pail, in which 300 grammes of potassium permanganate 

 are placed and 600 c.c. of formalin are added. The re- 

 action is violent, and is complete in about five minutes, 

 a maximum dosage of the room being quickly obtained. 

 Base modifies the method by using 300 c.c. of water with 

 375 grammes of potassium permanganate and 600 c.c. 

 of formalin, but finds the yield of gas less satisfactory. 

 The Military Commission in Vienna, on the contrary, 

 got better results by dilution of the strong formaldehyde 

 solution. Where portability of materials is important, 

 paraform and sodium bicarbonate solution may be sub- 

 stituted for formalin. 



On evaporation, molecules of formaldehyde condense 

 to form para-formaldehyde (polymerisation), (HCOH)w, 

 which has little disinfecting power, but which, on heating, 

 produces formaldehyde. Polymerisation seems to be 

 prevented to a large extent by the presence of moisture 

 (see also above). As a spray, formalin can be used in 

 any ordinary apparatus. It is stated by McLaughlin 

 that if the formaldehyde be mixed with phenol vapour, 

 polymerisation does not take place, and that therefore 

 the formaldehyde penetrates thoroughly. The mixture 

 he employs is 3 parts of 40 per cent, solution of formalde- 

 hyde with 1 part of carbolic acid. It may be volatilised 

 in a retort, or it may be simply poured on a sheet, which 

 is then hung up in the room to be ^disinfected. Base 

 quotes the conclusions of Werner as to the practical 

 requirements for an effective formaldehyde disinfection: 

 (1) 5 grammes of formaldehyde (absolute) should be 

 present in each cubic metre of space (0'1416 gramme per 

 cubic foot), and should be allowed to act for seven hours; 



