MICHIGAN ACADEMY OP SCIENCE. 145 



FORMALDEHYDE DISINFECTION BY MEANS OF POTASSIUM 



PERMANGANATE. 



E. M. Houghton, L. T. Clark. 



Formaldehyde has been recognized for several years as the most effi- 

 cient germicide available for disinfecting closed rooms and apartments. 

 Some difficulty has been encountered in devising a safe, economical, and 

 equally effective method for liberating the gas from its liquid or solid state, 

 that would do away with the necessity for expensive apparatus and an ex- 

 perienced operator. 



A'arious means have been employed for liberating the gas from saturated 

 aqueous solutions of formaldehyde and from it.s dry polymeric form, para- 

 form. The following methods have been the most extensively used: auto- 

 clave under pressure; retort without pressure; generator or lamp; formal- 

 dehyde and dry heat in partial vacuum; sheet spra3'ing; and heating para- 

 form. These several ways have had their respective good c[ualities as well 

 as their objectionable features. The autoclave under pressure and retort 

 without pressure are perpaps the most commonly used and rank among 

 the first in efficiency, but they also have serious deficiencies, requiring (1) 

 an expensive apparatus, (2) outside heat, (.3) an experienced operator. 



In January, 1904, Dr. G. F. Johnson, of Sioux City, Iowa, read a paper at 

 a meeting of the Sioux Valley Medical Association, in which he described 

 a new means for liberating formaldehyde from its solution for purposes 

 of disinfection. This method, conveniently called ''the formalin-perman- 

 ganate method," differs from others quite materially, as no outside heat is 

 recjuired. It consists in adding potassium permanganate crystals to full- 

 strength formaldehyde solution in a convenient receptacle placed in the center 

 of the room to be disinfected. Various proportions of permanganate and 

 formaldehyde have been employed, but McClintic, of the Department of 

 Public Health and jMarine Hospital Service, as the result of an elaborate 

 series of experiments, has recently reported that the best results are ob- 

 tained when fifty grams of potassium permanganate are brought in contact 

 with one hundred cubic centimeters of formaldehyde, or multiples of these 

 ciuantities, depending upon the space to be disinfected. Within a few sec- 

 onds to one minute, depending upon the size of crystals used and the tem- 

 perature of the room, a vigorous reaction ensues, causing strong ebullition 

 of the liquid and producing sufficient heat to liberate a large volume of 

 formaldehyde gas and water vapor. This boiling continues from four to 

 six minutes, becomes less vigorous, and gradually recedes until nothing re- 

 mains except the nearly dry residue. In many of our trials it became 

 thoroughly dry. In the majority of cases, however, this residue consisted 

 of a lower grade of manganese, a very small amount of formaldehyde, car- 

 bon dioxide, potassium hydrate and some moisture. According to McClintic 

 the liberation of the gas and water vapor is brought about according to the 

 following reaction: -4 K Mn04 + 3 HCOH + H20 = 4MnO (0H)2 + 

 2 K 2C03 + C02 (C02), the heat produced causing the liberation of form- 

 aldehyde and water vapor. Contrary to the general belief, the amount of 

 19 



