DESTR UCTION OF BA CTEEIA B Y CHEMICALS. 161 



The methyl-alcohol is oxidized and produces formal- 

 dehyde as follows: 



CH 2 OH + O = CH 2 O H 2 O. 



Formaldehyde is a gaseous compound having the 

 chemical formula CH 2 O and possessed of an extremely 

 irritating odor. At a temperature of 68 F. the gas 

 is polymerized that is to say, a second body is formed, 

 composed of a union of two molecules of CH 2 O. This 

 is known as a paraformaldehyde, and is a white, soapy 

 body, soluble in boiling water and alcohol; it exists in 

 the solution of commerce a clear, watery liquid con- 

 taining from 33 to 40 per cent, of the gas and 10 to 20 

 per cent, of methyl-alcohol, its chief impurity. If the 

 commercial solution ordinarily known in the trade as 

 "formalin" is evaporated or concentrated above 40 

 per cent., paraformaldehyde results; and when this is 

 dried in vaccuo over sulphuric acid a third body 

 trioxymethylene is produced, consisting of three mole- 

 cules of CH 2 O. This is a white powder, almost soluble 

 in water or alcohol, and giving off a strong odor of 

 formaldehyde. The solid polymers of formaldehyde, 

 when heated, are again reduced to the gaseous condi- 

 tion; ignited, they finally take fire and burn with a 

 blue flame, leaving but little ash. 



Formaldehyde has an active affinity for many organic 

 substances, and forms with some of them definite chem- 

 ical combinations. It combines readily with ammonia 

 to produce a compound called ammoniacal-aldehyde, 

 which possesses neither the odor nor the antiseptic 

 properties of formaldehyde. This action is made use 

 of in neutralizing the odor of formaldehyde when it is 

 desired to dispel it rapidly after disinfection. Formal- 



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