8 



STUDIES ON FKUIT RESPIRATION. 



use of air nearly or quite saturated with water vapor would cause 

 excessive humidity. The air entered each desiccator near the top 

 and was removed through a delivery tube reaching nearly to the 

 bottom. From the desiccator it was drawn through a Keiset absorp- 

 tion apparatus, then through another wash bottle containing baryta 

 water and to the suction pump. The air current was drawn through 

 at the rate of from 2 to 4 liters per hour. 



The desiccators were kept in the dark usually at some distance 

 from their respective sets of purifying and absorption apparatus. 

 The gases were led to and from them in copper tubes (one-fourth 



Fig. 1.— Purifying and absorption apparatus. 



inch outside diameter and one thirty-second inch wall) which pos- 

 sessed, in addition to the advantage of being infrangible, the property 

 of being easily bent into the required shapes. In all apparatus care 

 was taken to have the ends of the glass or copper tubes come together 

 closely at the joints, and to avoid entirely leading gases in rubber 

 tubes because of the well-known fact that rubber absorbs carbon 

 dioxid selectively. 1 The desiccators were of the tubulated Scheibler 

 pattern, 8 or 10 inches in diameter. No difficulty was experienced 

 in fitting the covers tightly, provided the glass surfaces were plane 

 and finely ground. The two-holed stoppers carrying the tubes were 

 well lubricated with vaseline, forced tightly into place, and tied. 



1 Morse, H. N., Exercises in Quantitative Chemistry, 1905, p. 77. 



