754 A MANUAL OF BACTERIOLOGY 



a deleterious action on articles, with the exception of 

 leather, as dry heat, while its penetrating powers are far 

 greater. By " saturated steam " is meant steam at the 

 temperature at which it can condense, and the tempera- 

 ture of the condensation point rises as the pressure 

 increases. By " superheated steam " is meant steam at a 

 temperature higher than that at which it can condense ; 

 therefore superheated steam has to be cooled down into 

 the state of saturated steam before condensation ensues. 

 If superheated steam is used for disinfection, it loses heat 

 by conduction, and the rise in temperature of the articles 

 treated approximately corresponds to the fall in tem- 

 perature of the steam. With saturated steam, on the 

 other hand, immediately it is cooled an enormous amount 

 of latent heat is set free by the change in state from the 

 gaseous to the liquid condition, therefore saturated steam 

 is a far more efficient disinfectant than superheated steam. 

 These considerations should always influence the choice 

 of a steam disinfecting apparatus for efficient working. 



The Equifex di&infector is worked with saturated steam 

 at 10 Ib. pressure (239 F.). The chamber consists of a 

 cylinder of mild steel, made without steam jacket, so as 

 to avoid risk of superheating. The cylinder is lagged with 

 non-conducting composition and wood, to reduce loss of 

 heat by radiation, and, as usually supplied, is furnished 

 with separate doors for infected and disinfected articles 

 respectively. An arrangement can be supplied to prevent 

 both doors being opened simultaneously. The Washing- 

 ton-Lyons apparatus, or its modifications, is an elongated 

 cylindrical boiler with double walls, forming a jacket, and 

 a door at each end. The chamber is of sufficient size to 

 admit bedding, and is built into the partition wall between 

 two rooms, so that each door opens into a different room. 

 Into one of the rooms the infected articles are conveyed, 

 and are placed in the disinfector as lightly packed as 



