BY STEAM 437 



same pressure. Saturated steam condenses immediately it meets the 

 object to be disinfected, and gives out its latent heat; superheated 

 steam acts by conduction, and not uniformly throughout the object. 

 Its advantage is, that it dries moistened objects. It differs physically 

 from saturated steam, because it does not condense (and give out its 

 latent heat), until its temperature falls. Therefore, as a disinfecting 

 power, superheated steam is much less than saturated steam, it has 

 less heat in it, so to speak, and it has less penetrative power. One 

 further term must be defined, namely, current steam. This is steam 

 escaping from a disinfector as fast as it is admitted, and may be at 

 atmospheric or higher pressures. The disinfecting temperature 

 which is now commonly used as a standard is an exposure to saturated 

 steam of 115° G.for thirty minutes. 



A number of different kinds of apparatus have been invented to 

 facilitate disinfection at this standard on a large scale. All the 

 larger Sanitary Authorities are now supplied with some form of 

 steam disinfector, though many are not furnished with high-pressure 

 disinfectors. Professor DeMpine has pointed out that a current of 

 steam at low pressure may disinfect completely.* Whilst such simple 

 current-steam machines have thus been demonstrated as efficient 

 bactericides, for practical purposes' it is important to have disin- 

 fectors, (a) capable of giving temperatures considerably above 100° C, 

 (6) of simple construction, (c) having a constant steam power of uni- 

 form temperature and rapid penetration, and (d) containing, when in 

 action, a minimum of superheated steam. In addition to these 

 characters of a first-rate steam disinfector, two other important 

 points in actual management should be borne in mind, namely, the 

 air must be completely ejected from the disinfection chamber before 

 the results due to steam are obtained, and some sort of automatic 

 indicator giving a record of each disinfection is indispensable. 



The five chief types of steam disinfectors in common use are, the 

 Washington Lyon, the G-oddard, Massey, and Warner, the Equifex 

 (Defries), the Thresh, and the Eeck.f 



Washington Lyon's apparatus consists of an elongated boiler 

 having double walls, with a door at each end. The body of the 

 apparatus is in a "jacket" for the purpose of preventing loss of heat 

 and for " drying " disinfected articles after the process. The whole is 

 large enough to admit of bedding and mattresses, and generally is so 

 arranged that one end opens into one room, and the other end opens 

 into another room. This convenient position admits of inserting 

 infected articles from one room and receiving them disinfected into 



* Jour, of State Med., December 1897, p. 561. 



t Full particulars of these various disinfectors may be obtained by communi- 

 cating with the makers. Elaborate catalogues are now issued with illustrations 

 and details of working. 



