204 PRACTICAL DIRECTIONS FOR DISINFECTION. 



to the penetration of porous, non-conducting articles, such as rolls of 

 blankets, clothing, etc. These points have been the subject of nu- 

 merous experimental investigations, and the principles involved 

 have been elucidated, especially by the investigations of Esmarch 

 (1887), of Budde (1889), and of Teuschner (1890). 



It has been shown that streaming steam is more effective than 

 confined steam at the same temperature, because it penetrates porous 

 objects more quickly. Also that superheated, " dry " steam is not as 

 effective as flowing steam at 100 C. ; on the other hand, it corre- 

 sponds in effectiveness with dry air, and the temperature must be 

 raised to 140 to 150 C. in order to quickly destroy the spores of 

 bacilli. 



Esmarch's investigations show that streaming steam penetrates 

 porous objects, like rolled blankets, more readily than confined 

 steam ; but the later researches of Budde and of Teuschner show 

 that a temperature of 100 C. is more rapidly reached in the interior 

 of such rolls when the flowing steam is under pressure. With the 

 same pressure (fifteen pounds) a temperature of 100 C. was reached 

 in two and one-half minutes when the steam was flowing, and in 

 eleven minutes by steam at rest (Budde). Intermittent pressure 

 was not found by Budde to present any advantages over continuously 

 flowing steam ; on the contrary, the time of penetration was longer. 



Teuschner, whose investigations are the most recent, arrives at 

 the following conclusions : 



1. Strongly superheated steam is not to be recommended for practical 

 disinfection. On the contrary, a slight supei-heating of the steam, such as 

 occurs in the apparatus of Schimmel, is not objectionable. 



2. Those forms of apparatus in which the steam enters from above are 

 much safer and quicker in their disinfecting action than those in which this 

 is not the case. In the construction of such apparatus care must be taken, 

 in order to secure penetration of the objects, that the air and steam have a 

 free escape below. 



3. Disinfection is hastened by previously warming the apparatus. 



4. The most rapid disinfecting action is secured by the use of streaming 

 steam in a state of tension (under pressure). 



5. Objects which have been in contact with fatty or oily substances 

 require a longer time for disinfection than those which have not. 



6. To accomplish disinfection it is necessary to expel, as completely as 

 possible, all air from the objects to be disinfected, and also to secure a suffi- 

 cient condensation of the steam. 



7. The condensation of the steam advances in a sharply denned line 

 from the periphery to the centre of porous objects. 



8. The temperature necessary for disinfection is only found in the zone 

 -where condensation has already taken place. 



9. Only a few centimetres from the zone in which the temperature is 

 100 C. when disinfection is incomplete there may be places in which 

 the temperature is 40 C. or more below the boiling point. 



