22 ANALYSES OF GAS ON THE EXTERIOR AND INTERIOR OF SOAP BUBBLES. 



maintained, and under what circumstances a state of equilibrium will ensue. I have 

 already stated that the condition of rest was simply an identity of composition of the 

 media on both sides the membrane, a law which is rigidly observed by all gases that 

 have yet been tried. Four hundred measures of nitrogen gas procured by phosphorus, 

 but which, by standing over water, were found to have gained 3| per cent, of oxygen, 

 were exposed to atmospheric air, in the apparatus above described, for thirty minutes : 

 at the end of that time, there were found four hundred and thirty-two measures in the 

 bubble, of which 15* per cent, were oxygen. Outside the bubble were ten hundred and 

 seventy measures, which also contained 15? per cent, of oxygen ; thermometer 57 Fah. 



60. Two hundred measures of nitrogen, containing the impurity as above, were ex- 

 posed for thirty minutes in an atmosphere of impure oxygen, which contained nitrogen 

 and carbonic acid, to the amount of 13^ per cent. : at the end of that time, three hun- 

 dred and sixty-one and a fourth measures were found in the bubble, of which 62 per 

 cent, were oxygen ; and eleven hundred and forty-four and a half measures were found 

 outside, 62i per cent, of which were oxygen ; thermometer 55 Fah. 



61. Two hundred measures of oxygen were exposed to an atmosphere of hydrogen 

 for fifteen minutes, at a temperature of 66 Fah. : at the end of that time, two hundred 

 and seven and three fourths were found in the bubble, containing 16?- per cent, of ox- 

 ygen ; and twelve hundred and seventy-three outside, which also contained 16f per 

 cent, of oxygen. 



62. The slower passing gases being thus found to obey a very simple law of equilib- 

 rium, attempts were made to ascertain whether such as carbonic acid, which are very 

 absorbable by water, followed the same law ; but, after many trials, no certain result 

 could be obtained, so rapid was the action. Five hundred measures thus confined 

 passed out immediately, the bubble collapsing almost as fast as it had been expanded : a 

 tube was therefore prepared, which had a roof of water at one extremity, about half an 

 inch thick and two inches in diameter; beneath this roof five thousand measures of car- 

 bonic acid gas were placed, and the arrangement exposed to the atmosphere. In forty- 

 eigbt hours, analysis showed that a trace of carbonic acid still existed in the tube, which, 

 when washed off, about two hundred measures of unabsorbable gas remained, con- 

 sisting of 20-5 oxygen, 79-5 nitrogen ; and therefore atmospheric air. This experiment 

 would thus warrant the conclusion that gases of any kind will pass a barrier, subject to 

 the same regulations as those that are less absorbable ; had it been allowed to continue 

 for a sufficient length of time, there can be no doubt that all the carbonic acid gas pres- 

 ent would have escaped into the atmosphere, and atmospheric air alone been present on 

 both sides of the barrier. 



63. Hence, the condition under which motion ceases through a barrier is identity of 

 chemical composition on both its sides. As gases, however, pass with different degrees 

 of velocity through the same liquid, results seemingly anomalous may be obtained, and 

 chemical decomposition may ensue ; if water recently boiled be exposed to the atmo- 

 sphere, it will be found in a few hours to have abstracted oxygen and nitrogen gases, 

 not in the same proportion, however, that exists in the circumambient air, for the gas 

 found in water contains 1 instead of i of oxygen ; perhaps in the course of time that 



