BY FORMALIN 443 



perfectly tight, and should be kept closed at least twenty hours." * 

 Calmette states that sulphur vapour under pressure may be relied 

 upon for the disinfection of ships, etc. 



Eecently, formalin has come much into favour as a room 

 disinfectant. Formalin is a 40 per cent, solution in water of 

 formaldehyde, 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. Its formula is CHgO, and it is a colourless 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 {GKfi^. This latter substance occurs in the stings of 

 bees, wasps, nettles, and various poisonous animal secretions. 

 Formalin is a strong bactericide even in dilute solutions, and, of 

 course, volatile. Its use should be restricted to disinfection of 

 articles injured by heat (furs, etc). A solution of 1-10,000 is said 

 to be able to destroy the bacilli of typhoid, cholera, and anthrax. A 

 teaspoonful to 10 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 spirit to produce the gas. Hence we have three 

 common forms of the same thing— /orma^m,/ormM aldehyde, para- 

 form — each of which yields formic acid, and thus disinfects. The 

 vapour cannot in practice be generated from the formalin as readily 

 as from the paraform. 



By a variety of ingenious arrangements, formic aldehyde has been 

 used by a large number of observers during the last two or three 

 years. We may refer to four modes of application : 1. The sprayer 

 produces a mixture of air and solution for spraying walls, ceilings, 

 floors, and sometimes garments. There are a number of different 

 forms of spraying apparatus such as the Equifex, the Mackenzie, 

 the Eobertson, etc. 2. The autoclave (Trillat's apparatus). In this 

 apparatus a mixture of a 30-40 per cent, watery solution of 

 formaldehyde and calcium chloride (4-5 per cent.) is heated under 

 a pressure of three or four atmospheres, and the almost pure, dry 

 gas is conducted through a tube passing through the keyhole of the 

 door into the sealed-up room. 3. The paraform lamp (the Alformant). 

 The principle of this lamp is that the hot, moist products from the 

 combustion of methylated spirit act upon the paraform tablets, 

 converting them into gas. 4. Lingner's apparatus consists of a ring 

 boiler in which steam is generated and driven into a reservoir filled 



* Tenth Report of State of Maine Board of Health, 1898, p. 365. This report 

 contains a digest on the whole subject of disinfection. 



