136 A CHEMICAL SIGN OF LIFE 



analysis is done immediately after the respiration, dur- 

 ing which the variation in temperature and pressure 

 will not affect the results beyond experimental errors, 

 as is shown in the following calculation: 



Let us suppose that 10 mg. of the tissue respire for ten 

 minutes at 18 C. under 760 mm. of pressure in 25 c.c. 

 of the chamber, and suppose i . 5 c.c. of the air at 22 C. 

 and 730 mm. of pressure gave the first precipitate. We 

 shall then obtain the following results: 



a) Without correction we get 



i . oX IQ 7 g.X = 16 . 6X io~ 7 g. 



b) With a correction, 



(270+ 2 2) X 760 



This shows a little over 5 per cent error, which will be 

 the maximum and almost an impossible variation, con- 

 sidering the ordinary weather in the laboratory for a 

 short interval of time. Besides, we are dealing with a 

 very small sample of moist tissue, the weight of which 

 may easily vary within 5 per cent. 



