Becker — Apparatus for Observing Reaction between Gases, etc, .'537 



adjusted by means of a screw, so that the whole is water-tight. In addition, 

 the glass part of the stirrer is expanded into a cone at the lower end, which 

 is ground to fit a corresponding cone on the bearing, so that the metallic 

 parts of the stirrer do not come into contact with the liquid at any point. 



The glass part of the stirrer is so designed that, when rotated at a high 

 speed, it causes a stream of fine bubbles of the gas to circulate through the 

 liquid, thus ensuring equilibrium between the liquid and the gas. 



The manometer is provided with a scale of millimeters etched on the 

 glass. 



IV. — Calibration of the Apparatus. 



In order to check the formula derived for the calculation of the volume 

 of gas absorbed, use was made of ferrous hydrate as an absorbent for oxygen. 

 The following experiments were made :■ — 



The apparatus was filled with 110 c.c. of distilled water which had been 

 previously saturated with air at 20° C. by bubbling air through it for some 

 hours, and the water circulation from the thermostat through the water- 

 jacket started. When everything was in equilibrium, about 25 c.c. of the 

 water was withdrawn, and in place of it was added exactly 10 c.c. of a 

 solution of ferrous sulphate containing 8*2 grams per litre, followed by 10 c.c. 

 of a 10 per cent, solution of sodium carbonate, the whole being carefully 

 washed into the apparatus. The barometer was then read, and the taps of 

 the apparatus having been suitably adjusted, the stirrer Avas started, and the 

 manometer watched until the reading became constant. The inaximum 

 reading was then used to calculate the volume of oxygen absorbed by the 

 ferrous hydrate. 



Experiment A. — Temperature, 20'0° C ; barometer, 768T mm. 

 Maximum reading of manometer, . 114'0 divisions. 



Second reading after resetting to zero, . 5-5 „ 

 114 divisions at 768T mm. correspond to 1'525 c.c. 

 o"5 „ „ „ "UYo „ 



Total, 1-598 



Total volume absorbed, calculated for N.T.P. = 1'504 c.c. 



Experiment B. — Temperature, 20'0° C. ; barometer, 769.9 mm. 

 Maximum reading of manometer, 118 divisions. 



118 divisions at 769'9 mm. correspond to 1'610 c.c, which at N.T.P. 

 reduces to 1'520 c.c. 



The mean of the two experiments gives 1"512 c.c. absorbed. 



Since the partial pressure of the oxygen in the air in the vessel was 



2s2 



