DISINFECTION 



333 



SO 2 in the air in the centre of the room at a height of four 

 feet, and after the lapse of four hours. There can be little 

 doubt that fuming a sealed-up room with sulphur fumes in 

 a moist atmosphere, and leaving it thus for twenty-four 

 hours, is generally, if not always, efficient disinfection. It 

 will kill the bacillus of diphtheria, though not always more 

 resistant germs. Moreover, its simplicity of adoption is 

 greatly in its favour. Anyone can readily apply it by pur- 

 chasing a few pounds weight of ordinary roll sulphur and 

 burning this in a saucer in the middle of a room which has 

 had all its crevices and cracks in windows and walls blocked 

 up with pasted paper. Nitrous fumes may also be used in 

 this way. 



Recently formalin has come much in favour as a room 

 disinfectant. Formalin is a 40 per cent, solution of form- 

 aldehyde in water, a gas discovered by Hofmann in 1869. 

 This gas is a product of imperfect oxidation of methyl 

 alcohol, and may be obtained by passing vapour of methyl 

 alcohol, mixed with air, over a glowing platinum wire or 

 other heated metals, such as copper and silver. It is the 

 simplest of a series of aldehydes, the highest of which is 

 palmitic aldehyde. Its formula is CH 3 O, and it is a colour- 

 less gas with a pungent odour, and having penetrating and 

 irritating properties, particularly affecting the nasal mucous 

 membrane and the eyes of those working with it. It is 

 readily soluble in water, and in the air oxidises into formic 

 acid (CH 2 O 3 ). This latter substance occurs in the stings 

 of bees, wasps, nettles, and various poisonous animal secre- 

 tions. Formalin is a strong bactericide even in dilute 

 solutions, and, of course, volatile. A solution of I to 

 10,000 is said to be able to destroy the bacilli of typhoid, 

 cholera, and anthrax. A teaspoonful to ten gallons of milk 

 is said to retard souring. When formalin is evaporated 

 down, a white residue is left known as paraform. In lozenge 

 form this latter body is used by combustion of methylated 



