466 GERMICIDES — DISINFECTANTS 



Chlorine is generally used in the form of the hypochlorites which 

 easily liberate chlorine. Chlorinated lime (improperly called chlor-. 

 ide of lime), bleaching powder, is a mixture of hypochlorites. 



Iodine is employed in the free state as the tinctiire, Lugol's solu- 

 tion, ointment and in various combinations with organic matter of 

 which iodoform may be taken as an example. 



Tincture of iodine is a favorite disinfectant for operating areas 

 and infected wounds. For details of the halogens see p. 371. 



MISCELLANEOUS DISINFECTANTS 

 FORMALDEHYDUM 



Synonym. Formic Aldehyde 



This is a colorless gas formed by oxidizing methyl alcohol. It is 

 official in a 37 per cent, solution in water, under the name of Liquor 

 Formaldehydi. Formalin is a similar product. Formalin or solu- 

 tion of formaldehyde is a clear colorless liquid, having a pungent 

 odor and caustic taste. It is miscible in all proportions with water 

 and alcohol. 



Action. Formaldehyde is one of the most powerful germicides 

 and has the advantage of being volatile and very penetrating. It 

 prohibits the growth of bacteria in 1 : 500 to 1 : 20,000 (pure 

 formaldehyde) ; formalin requires 2% times as much. It also checks 

 growth in 1 : 30,000 of most organisms and solutions of 1 : 2% per 

 cent, kill most bacteria together with their spores, according to spe- 

 cies and time of exposure. The gas is more active, in the presence of 

 moisture. It surpasses most disinfectants in penetrating power and 

 does not injure metal or clothing, so is very serviceable for disinfect- 

 ing rooms, etc. 



Formaldehyde vapor is very irritating to the mucous membranes 

 even in dilute solutions but animals and man soon gain a tolerance 

 for it. It toughens the unbroken skin, making it rough and white, 

 and produces anesthesia. Strong solutions or repeated applications 

 may lead to superficial necrosis. These effects are produced by 

 coagulation of the proteids with which it forms actual combinations. 

 It has no effect upon pepsin, rennin or malt but diminishes the ac- 

 tivity of papain, trypsin and amylopsin. When inhaled, even for a 

 long time, there is little if any effect aside from some local irrita- 

 tion, which may lead to bronchitis or pneumonia. Intravenous in- 

 jections of 1 : 5000 in physiological saline produce no physiological 

 action. Oral doses have little if any immediate action aside from 

 irritation. 



The antidote to local action is ammonia or the ammonium salts. 

 The irritant action of formaldehyde can be largely eliminated by 

 using it in the form of some of its condensation products, from which 

 it is eliminated slowly. It has the property of forming more or less 



