$14 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Manipulation* 



If the apparatus has been recently pieced together it is necessary to fill 

 the connections with nitrogen. This is done in the same way as in an analysis 

 of gas : 



Both the control tube (C) and the potash bulb are connected to the 

 atmosphere through M and to one another. The level of the potash is then 

 put at the mark (N) by adjusting the height of R. The tap (M) is closed and 

 is not turned again until the analysis is finished. 



The tap (T) is opened to the air and air is drawn into the gas burette by 

 lowering the levelling tube. The tap is closed to the air. The volume is 

 read by turning the tap to connect S and G and adjusting the levelling tube so 

 that the potash stands at F. The tap being open to the potash absorption bulb, 

 the gas is driven out of the burette until mercury just reaches the tap (T) 

 which is closed. After some minutes, to allow absorption to occur, the tap 

 (T) is opened and the levelling tube lowered until the gas returns to the burette 

 and the potash stands at F and also at N. The latter position is adjusted by 

 moving R. The volume is noted. The gas is now driven into the bulb (P) by 

 raising the levelling tube and turning the 3-way tap to the bulb (P). After 

 some minutes it is returned to the gas burette by lowering the levelling tube 

 and allowing the pyrogallol to reach the mark (H). The gas is driven over 

 several times into the pyrogallol until on measuring the volume it remains 

 the same. 



A small quantity of oxygen remains between the 3-way tap and F. This 

 is absorbed by driving the gas again into the potash bulb, returning it to the 

 burette and then driving it into the pyrogallol. The gas is returned to the 

 burette leaving the pyrogallol standing at H and the 3-way tap turned. 

 Before finally reading the volume, the gas is driven again into the potash 

 bulb, the level at N adjusted by R, and returned to the burette leaving the 

 potash at F. The volume is read off. The capillary tubes are thus filled with 

 nitrogen and the compensation for changes of temperature have been made. 



An analysis of gas is made in the same way after driving out the nitrogen 

 in G through T to the air and drawing in the sample to be analysed. 



The Analysis of Atmospheric Air, Expired Air and Alveolar 



Air with Haldane's Gas Analysis Apparatus. 

 ( I ) A tmospheric A ir. 



The air from the room is introduced into the gas burette by lowering the 

 mercury levelling tube. 



The direct estimation of the amount of carbon dioxide may be neglected 

 as this gas is present in such small amounts. The analyses should be 

 repeated until the correct figures (20^96 per cent.) are obtained for atmospheric 

 oxygen. 



