OXYGEN RESPIRATION 43 



Some experiences show that it is possible to carry out a series 

 of exact analyses in a short time in the apparatus of Polowzow- 

 Richter, since each analysis requires but 20-30 minutes and the 

 apparatus can at once be used again after completing an analy- 

 sis.-' For the physiologist it is of great importance that the 

 apparatus makes possible the analysis of very small amounts of 

 gas. Other merits of the apparatus are: simplicity of construc- 

 tion, inexpensiveness, and the small quantity of mercury 

 required for the analyses. 



In the original model of Polowzow, oxygen was determined 

 by absorption with an alkaline solution of pyrogallol. The 

 essential modification introduced by Richter consisted in 

 the determination of oxygen by explosion with hydrogen. The 

 use of the explosion pipette makes possible a more rapid and, at 

 the same time, a more accurate determination of oxygen. 

 Moreover, the modified apparatus is useful for determinations 

 of hydrogen, carbon monoxide and other gases. 



The manipulation of the apparatus of Bonnier and Mangin^ 

 is simpler. However, it yields less accurate results. In this 

 apparatus the determinations of CO2 are rehable up to 0.3%, 

 the oxygen determinations, to 0.5%. This accuracy is entirely 

 satisfactory in many cases; moreover the apparatus is so con- 

 structed that it is conveniently portable and can thus be used 

 on trips and excursions. Fig. 7 represents the small model of 

 the apparatus, which is mounted on a wooden base, and, packed 

 in a specially fitted wooden box, is particularly suitable for 

 carrying about. 



The horizontal portion of the measuring tube R is divided 

 into milhmeters. The twice-bent end of the measuring tube 

 is immersed in mercury in the bath W. The piston S with 

 handle, moved by means of a screw thread in a metal shell filled 

 with mercury, serves for the introduction and expulsion of gases 

 and reagents. 



The analyses of gas are carried out in this apparatus as 

 follows. The analysis tube with gas contained therein is placed 



1 After closing a series of analyses the mercury bath C must be emptied at once and the 

 level of mercury somewhat lowered in the capillary tube of the absorption pipette. 



2Aubert. Rev. gen. de bot. 3: 97- 1891. (Thoday (Ann. of Bot. 27: 5(^5-573. I9i3^ 

 gives the detailed procedure, and mentions important precautions to be observed, when 

 using this apparatus.] 



