THE DESTRUCTION OF BACTERIA 



91 



volume of formalin solution used. By using 1.5 liters of 8 per cent 

 formalin for each 1,000 cubic feet of space, this apparatus is said to 

 yield a concentration of formaldehycl of about 25 grams to the cubic 

 meter. 



To do away with the use of liquid, a method has been devised 

 which depends in principle upon the breaking up by heat of the solid 

 polymer of formaldehyd (tri- 

 oxymethylene) . The apparatus 

 (trade name, "Schering's Para- 

 form Lamp") as described by 

 Aronson l consists of a cylindri- 

 cal mantle of sheet-iron placed 

 upon a stand and supplied be- 

 low 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, 



77 \\ 



FIG. 13. BRESLATT FORMALDEHYD GEN- 

 ERATOR AND SECTION OF SAME. (After v, 

 Brunn.) a, Inlet; b, Exit vent. 



so placed that the wicks project 



but slightly to avoid overheating is lighted, and the formalin gen- 

 erated passes out through slits in the upper case, mingling with the 

 water vapor and other gases liberated by the alcohol flame. The 

 more modern devices have water-boiler attachments to insure suffi- 

 cient 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 room. 



A simple method of generating formaldehyd is that which is known 

 as the "lime method." In a wide shallow pan 40 per cent formalde- 

 hyd solution (commercial formaldin) is poured over quicklime (CaO) . 

 The previous addition of concentrated sulphuric acid to the formalin, in 

 proportions of one to ten, increases the speed of formalin liberation, and 

 aids in limiting polymerization. One and one-half to two pounds (one- 

 half to one kilogram) of quick-lime are used for every 500 c.c. of the for- 

 malin solution. The heat generated in the slaking of the lime produces 

 volatilization of the formalin. 



A modification of this method is that of Sobering 2 in which tab-' 



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



2 Schering, Hyg. Rundschau, 1900. 



