574 Experiments 



If we examine Column 9, we see that the carbonic acid obeys the 

 law given, up to a pressure corresponding to 5 or 6 atmospheres of 

 air; but from there on. the product CO., x P decreases rapidly. On 

 comparing Columns 7 and 9 with Columns 6 and 8 of Table VII, 

 we find numbers that are quite analogous, and that indicate a simi- 

 lar intervention of the fatal action of oxygen. It becomes very 

 evident, when the tension of this gas can be represented by 150, 

 that is, when it corresponds to an atmosphere and a half of pure 

 oxygen, or 7 atmospheres of air. 



In Figure 7, the lower line C expresses the numbers of Column 

 9; we see that for the same barometric pressures it remains far 

 below line B, which represents the results of the experiments in 

 which ordinary air was used. 



Finally, Column 6 shows, as did Column 4 of Table VII, that the 

 duration of life, referred to a liter of ordinary air under normal 

 pressure, continues to decrease with astonishing rapidity, when the 

 pressure, or rather the oxygen tension, increases. 



It is therefore overwhelmingly proved that oxygen, under a 

 certain tension, is a dangerous agent which, in compressed air in 

 closed vessels, first joins its action to that of the carbonic acid 

 produced, and which for high tensions is the principal, soon the 

 only, cause of death; this tension, measured by the expression 

 O. x P, can be reached, according to the statement already made 

 so often, by increasing either the barometric pressure P, or the 

 percentage of 2 . 



But it is established at the same time that the formula previously 

 given, The death of sparrows occurs when the tension of the car- 

 bonic acid, measured as I have specified, is represented by a figure 

 which oscillates between approximately 24 and 30, expresses the 

 truth. To prove it experimentally one need only guard against the 

 excess of oxygen. 



F. Compression with ordinary air: elimination of carbonic acid. 



The presence of carbonic acid had prevented me, as we have just 

 seen, from finding the real law which determines the exhaustion of 

 the oxygen of compressed air for animals allowed to die in closed 

 vessels. 



But the fatal action of compressed oxygen which the studies 

 just discussed had revealed to me no longer permitted me to think 

 that the simple law, established for pressures lower than one at- 

 mosphere, could continue to be applicable to higher pressures. 



It was, however, necessary to determine the facts. Apparently 



