APPENDIX 395 



ultra violet most active. Direct sunlight kills plague bacilli in less than one hour 

 typhoid bacilli in six. 



(2) Burning. Very efficient but expensive. 



(3) Boiling. Especially m carbonate of soda solution for about one hour is a 

 very efficient disinfectant. Nonspore-bearing bacteria are killed almost instantly 

 by a boiling temperature. One must remember that the boiling temperature is 

 lower at mountainous elevations. 



(4) Steam. Extremely efficient. The condensation of the steam on the object 

 to be sterilized gives off latent heat and produces a vacuum. 



(B) Of the gaseous disinfectants we have the very efficient germicide formal- 

 dehyde gas and the weakly germicidal, but potent insecticide, sulphur dioxide. 



Formaldehyde gas is practically valueless as an insecticide. 



Bromine, chlorine and hydrocyanic acid gas have a certain degree of efficiency 

 but are not of practical application. Hydrocyanic acid gas is especially dangerous 

 on account of its extreme toxicity. 



(i) Formalin. This is a 40 % solution of formaldehyde gas, but is as a rule 

 of less strength from evaporation or otherwise. Formaldehyde is efficient as a 

 surface disinfectant when the temperature is above 50 F. and the air contains at 

 least 60 % of moisture. It is not efficient in cold dry rooms. Owing to its lack 

 of penetrating power it is not efficient for the disinfection of mattresses, or similar 

 articles. To prepare a room for disinfection we must measure the cubic space 

 to ascertain the necessary amount of formalin to use and stuff up or better paste 

 up with newspaper all cracks and openings. 



In the production of formaldehyde gas the more expensive autoclaves and lamps 

 have largely been replaced by the simple formalin permanganate method. In this 

 one pours 500 c.c. of formalin on 250 grams of potassium permanganate for each 

 1000 cubic feet with six to twelve hours' exposure. 



In employing this method, take a pan partly filled with water. Place in this 

 a second metal or glass receptacle containing the permanganate. Then pour the 

 formalin on the permanganate crystals.. The gas is generated in great amount in 

 a few seconds. The receptacle containing the permanganate and formalin should 

 be large enough to contain ten times the volume of formalin, as there is a tendency 

 for the mixture to foam over the sides of the dish. 



Another practical method is the formalin-sheet-spraying one. The formalin 

 (40%) should be sprayed on sheets suspended in the room in such a manner that 

 the solution remains in small drops on the sheet. Spray not less than 10 ounces 

 of formalin (40%) for each 1000 cubic feet. Used in this way a sheet will hold 

 about 5 ounces without dripping or the drops running together. The room must 

 be very tightly sealed in disinfecting with this process and kept closed not less than 

 twelve hours. The method is limited to rooms or apartments not exceeding 2000 

 cubic feet. The formalin may also be sprayed upon the walls, floors, and objects 

 in the rooms. 



Paraform Lamps. For single rooms the use of the paraform lamp is quite con- 

 venient. Special lamps can be obtained to burn the paraform tablets or a pint 

 tincup will suffice for the heating of i ounce of paraform. The lamp or alcohol 

 flame under the receptacle must not be high enough to ignite the paraform which 

 burns readily and in so doing does not give off formaldehyde gas. One ounce of 



