ORGANIC COMPOUNDS 147 



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 crj^stals 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 8i 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 bicliromate, 10 ounces. 



2. Saturated solution of formaldehyde, 16 ounces. 



3. Common sulphuric acid, IJ ounces. 



Two and 3 are mixed together and when cool are 

 poured on the bichromate, which is placed in an earthen- 

 ware jar of a volume about ten times the quantity of fluid 

 used. The quantities given are for each 1000 cubic feet of 

 space. 



A very simple method is to cause the formalin, diluted 

 about twice with water to furnish moisture enough, to drop 

 by means of a regulated ''separator funnel" on a heated 

 iron plate. The dropping should be so regulated that each 

 drop is vaporized as it falls. The plate must have raised 

 edges, pan-shaped, to prevent the drops rolling off when they 

 first strike the plate. Formaldehyde has no corrosive (except 

 on iron) or bleaching action, and is the most nearly ideal 

 closed space disinfectant today. In disinfecting stations it 

 is made use of in closed sterilizers such as were described 

 under steam disinfection, particularly in connection with 

 vacuum apparatus. It is also used in solution as a pre- 

 servative and as a disinfectant. The commonest strength is 

 2 or 3 per cent of formalin or 0.8 to 1.2 per cent of the 

 formaldehyde gas. As an antiseptic it is efficient in dilu- 



