76 MICROBIOLOGY 



slightly soluble in water and alcohol. To summarize, formal- 

 dehyde exists in three states. 



CH 2 



CH 2 CH 2 



CH 2 CH 2 O CH 2 



Formaldehyde gas. Paraformaldehyde, Trioxymethyleiie. 



Paraform. 



Paraform is obtained in the market and is put up by 

 certain manufacturers in the form of paraform candles, in 

 such quantities that one candle liberates gas sufficient for 

 1,000 cu. ft. of space. When used the room or stable must be 

 tightly sealed. 



Formaldehyde is used practically by saturating sheets or 

 blankets with formalin and suspending them in the room, 

 using at the rate of 10 oz. of formalin for each 1,000 cu. ft. 

 of space. 



Sulphuric and crude carbolic acids. This consists of a 

 mixture of these acids. It is quite corrosive and care should 

 be taken to protect the eyes and the hands from accidental 

 splashing : 



Crude sulphuric acid % gallon. 

 Crude carbolic acid % gallon. 



These two substances should be mixed in wooden tubs or glass 

 vessels. The sulphuric acid is very slowly added to the car- 

 bolic acid. During the mixing a large amount of heat is de- 

 veloped. The disinfecting power is heightened if the amount 

 of heat is kept down by placing the tub or demijohn contain- 

 ing the carbolic acid in cold water, while the sulphuric acid is 

 being added. The resulting mixture is added to water in the 

 ratio of 1 to 20. One gallon of mixed acid will thus furnish 

 20 gallons of a strong disinfecting solution having a slightly 

 milky appearance. The mixture should be applied to the walls 

 and floors of the pens, saturating them with it. 



Sulphur. Sulphur is one of the oldest disinfectants. 

 Sulphur dioxide gas (S0 2 ) has been extensively used for the 



