Thin Fabrics and Films to Hydrogen and Helium. 279 



Table II. 



(a) Hydrogen. 



Transfusion of gas in c.c. 

 Duration of film. Temp. per sq. cm. of film per hour. 



H. min. °C 



1 52 18-6 48 



1 35 200 5'2 



59 201 42 



1 45 196 4-3 



1 20 20-S 3'5 



1 10 197 4-1 



1 07 19T 3-8 



4 40 19-2 31 



19T 31 



19-2 3-8 



19T 36 



Average 4 



(b) Helium. 

 3 41 



5 15 



18-4 



3-0 



18-3 



2-4 



18-0 



31 



19-5 



2-2 



19-3 



2-8 



18-7 



2-8 



18-7 



3-1 



Avero 



ge 2-8 



hydrogen to be 960 and for helium 670 litres per square metre 

 per day. For the most highly porous balloon fabrics tested 

 by Elworthy and Murray the transfusion of hydrogen was 

 only about 10*0 litres per square metre per day, and of 

 helium 7*1 litres per square metre per day. It is interesting 

 to note that while soap films were very much more permeable 

 to hydrogen and helium than were the balloon fabrics tested, 

 the ratios of the permeabilities of both fabrics and films to 

 the two gases were practically the same. This is the mora 

 interesting when it is considered that while in the case of 

 the films the membrane was of the continuous type, in the 

 case of the fabric there was a possibility of the diaphragm 

 being discontinuous. It may ba, however, that on account 

 of the fabrics being " doped " the discontinuity referred to 

 was negligible. In this case the process of transfusion of the 

 gases through the substance of the fabric would probably 

 be of the same nature as that of transfusion through the 

 films. 



