THE DESTRUCTION OP BACTERIA 



91 



.^,^J^ 



strong copper kettle of about 34 cm. diameter by 7.5 cm. height. 

 This is completely closed except for two openings in the slightly 

 domed top, one of which is the exit vent, the other, laterally 

 placed, is for purposes of filling and is closed by a screw stopper. 

 The kettle is set up on a metal stand over an alcohol lamp, so arranged 

 with a double circle of burners that heating may be carried out rapidly. 

 The tank is filled with a solution of formalin of a strength of from 8 to 

 10 per cent (commercial formalin 1:4). The apparatus permits the 

 evaporation of large quantities of fluid in a short time (3 hters in one 

 hour). When the lamp is left in a closed room care should be taken 

 to fill it with a quantity of alcohol proportionate to the amount of fluid 

 to be evaporated. This, according to v. Brunn, is about one-quarter 

 of the volume of formalin solu- 

 tion used. By using 1.5 liters of 

 8 percent formalin for each 1,000 

 cubic feet of space, this apparatus 

 is said to yield a concentration 

 of formaldehyde of about 25 

 grams to the cubic meter, a 

 strength sufficient to complete 

 surface disinfection within seven 

 hours. 



To do away with the use of 

 hquid formalin solutions, a meth- 

 od has been devised which de- 

 pends in principle upon the breaking up by heat of the solid polymer 

 of formaldehyde (trioxymethylene) . The apparatus (trade name, 

 "Schering's Paraform Lamp") as described by Aronson ^ consists of a 

 cylindrical mantle of sheet-iron placed upon a stand and supplied 

 below with an alcohol lamp. Set into the top of the mantle is a small 

 chamber, into which 1 gram tablets of trioxymethylene are placed. 

 The alcohol lamp, so placed that the wicks project but slightly — to 

 avoid overheating — is lighted, and the formalin generated passes out 

 through slits in the upper case, minghng with the water vapor and other 

 gases liberated by the alcohol flame. The more modern devices have 

 water-boiler attachments to insure sufficient moisture. Two tablets 

 are sufficient for the fumigation of about thirty-five cubic feet, and 

 2 c.c. of alcohol are filled into the lamp for each tablet. One hundred 

 to one hundred and fifty tablets are usually enough for the ordinary 

 1 Aronson, Zeit. f. Hyg., xxv, 1897. 



77 ^ 



Fig. 13. — Bheslau Formaldehtdb 



Generator and Section of Same. 



(After V. Brunn.) a, Inlet; 6, Exit vent. 



