372 APPLIKD BACTEKIOLOGY 



and bell should be flexible, silk-covered wires, and it is 

 convenient to have them of different colours. 



The wires can be pinched tight between the door and 

 the machine, so as to prevent escape of the steam without 

 fear of cutting the wires. One battery and bell is sufiicient 

 for several thermometers, each thermometer being discon- 

 nected as the mercury rises and makes connection. 



A good electric thermometer should ring in fifteen 

 seconds on being plunged into boiling water. Suitable 

 thermometers can be obtained from J. J. Hicks, of Hatton 

 Garden. 



In testing a high-temperature disinfector, using an 

 electric and a maximum thermometer together within 

 several folds of blankets, and turning off the steam directly 

 the electric thermometer (set to ring at 100° C.) rang, it 

 would be expected that the maximum thermometer would 

 also register 100° C, or only a little above. This is not 

 the case, as the maximum thermometer may be found 

 registering several degrees higher. A satisfactory ex- 

 })lanation of this is not at present forthcoming. 



The presence or absence of superheat is tested by com- 

 paring the pressure in the disinfecting chamber as measured 

 by a pressure-gauge with the temperature obtained in 

 various parts of it. In the case of non-pressure disinfectors 

 the barometric pressure is the pressure in question. Keg- 

 nault's tables, stating the temperature of saturated steam 

 at various pressures, will enable the results to be interpreted. 

 The presence or absence of air at any epoch can be tested 

 by condensing the exhaust steam in a tube provided with 

 a cock on the side next to the disinfector and dipping into 

 water. If it is free from air, the tube will fill completely 

 with water ; if not, the residual air will collect at the top. 



A steam disinfector should be examined for uniformity of 

 temperature in various parts of the disinfecting chamber. 



