AUTOCLAVES 



11 



It is obvious of course that a sufficient quantity of water must be put 

 into the boiler before commencing the sterilization. Heating should never 

 be continued for longer than 30 to 40 minutes in case the boiler should 

 boil dry. 



2. Ducretet and Lejeune's autoclave. The principle and working of the 

 instrument are the same as in the case of Chamberland's autoclave. The 

 tall form of boiler however makes it especially useful for the sterilization 

 of long pieces of apparatus and of porcelain filter bougies ; as many as thirty 

 of the latter can be accommodated at one and the same time by means of a 

 special pattern of support. The autoclave will withstand a pressure of 

 3 or 4 atmospheres, and is strong enough to be used for sterilization by 

 means of compressed carbonic acid (d' Arson val). 



To facilitate manipulation, some minor alterations have been introduced in the 

 construction of the newest models of autoclaves. For instance, in one made by 

 Adnet the cover is secured by a gearing controlled by a single screw instead of by 

 bolts. In another, made by Rongier, the cover is fitted with an hinge, and in yet 

 another, by Radias, with a lever. 



3. Vaillard and Besson's autoclave. In large laboratories where, for 

 instance, toxins for immunizing horses in the preparation of therapeutic 

 serums or for other purposes are required in 



large bulk, and the consumption of media is 

 considerable, it is necessary or at least con- 

 venient to have some more commodious form 

 of autoclave than Chamberland's. In such 

 cases Vaillard and Besson's pattern is available 

 (%. 7). 



This autoclave l consists of a large cylindrical boiler 

 with double walls. The apparatus to* be sterilized is 

 arranged on shelves in a central space. The steam 

 rising from the water in the double bottom ascends 

 between the inner and outer walls, passes through the 

 sterilizing chamber from above downwards, and escapes 

 through a safety valve, the escape being regulated in 

 such a .manner that the pressure and therefore the tem- 

 perature rise gradually. When the temperature reaches 

 115 C., the safety valve automatically allows the steam 

 to escape sufficiently to prevent any further increase 

 of pressure. The boiler is also fitted with a lateral 

 funnel through which the water may be poured in, a 

 tap by which the level of the water is regulated, a 

 manometer and a safety valve. The construction of 



this apparatus is such that sterilization is effected in a current of steam, and a further 

 advantage is that all the air is expelled without resort to decompression, the disadvan- 

 tages of which have already been noted. 



Technique. (a) Place the apparatus in the chamber S, and secure the cover firmly 

 by means of the screw bolts. (6) Open the tap of the lateral supply funnel and pour 

 in water until it runs out at P, which must also have been previously opened ; then close 

 both taps and raise the valve D. (c) Light the stove. (In France charcoal is generally 

 used as the source of heat, but the autoclave is also constructed to work with gas.) (d) As 

 soon as the water boils, steam will rise between the inner and outer walls, enter the steriliz- 

 ing chamber, and escape by way of the tube leading to D. When the pressure is sufficient 

 to cause the steam to issue in a powerful jet, lower the valve D. The temperature and 

 pressure within the autoclave will now rise, and will be registered on the manometer M. 

 The steam escapes more and more violently as the pressure increases, until the tem- 

 perature for which the valve has been regulated (usually 115 C.) is reached, when 

 the volume of escaping steam is such as to prevent any further rise of temperature. The 



1 Annalea de V Institut Pasteur, 1894. 



FIG. 7. Vaillard and Besson's 

 autoclave. 



