74 COMPARISONS OF RESPIRATORY EXCHANGE. 



upper right-hand portion of the apparatus. This combustion pipette 

 is provided with a three-way stopcock. The ignition tubes inside the 

 pipette have been removed and it has been filled with stick yellow 

 phosphorus of suitable length and amount, so that 21 c.c. of air can be 

 introduced into the combustion pipette. A leveling bulb, S, containing 

 water, is attached by means of rubber tubing to the lower portion of 

 the combustion pipette. It has been possible with this arrangement to 

 compare directly on the same apparatus the absorption of oxygen by 

 means of potassium pyrogallate and the absorption of oxygen by means 

 of phosphorus. 



METHOD OF USE. 



An analysis of atmospheric air or expired air is carried out in the 

 following manner: The air in the apparatus is first freed from carbon 

 dioxide and oxygen, in order that all of the capillaries may be filled 

 with nitrogen. A small portion of air is then drawn into the apparatus 

 through the stopcock, C, at the top of the burette, A, passed into the 

 potash in E, and then into the potassium pyrogallate in L until constant 

 readings are obtained. Before any readings are made the levels 

 on the potash pipette are set. This is done by lowering the mercury 

 and shutting the stopcock, Q, when the mercury has come to the proper 

 point, making the final adjustment by means of the adjustment 

 screw, P, at the bottom. The angle stopcock, F, situated between the 

 potash pipette, E, and the potassium pyrogallate pipette, L, is then 

 turned so that communication exists between the burette, A, and the 

 potash pipette, E. The stopcock, J, situated between the potash 

 pipette and the compensating tube, is then opened to the air, and the 

 levels in the tube leading from the potash pipette, E, and in the tube 

 connecting the compensating tube, K, and the potash pipette, E, with the 

 three-way stopcock,/, are set. It is advisable to place leveling marks 

 on these two tubes when the apparatus is first put into use by taking 

 out the three-way stopcock, J, and the angle stopcock, F, and allowing 

 the liquid to settle to its own level. The two levels will then obviously 

 be at atmospheric pressure. After these two levels have been set, 

 the three-way stopcock, /, connecting the potash pipette and the 

 compensating tube, is closed and there is no need of opening it again 

 during any immediately succeeding analysis or series of analyses. It 

 must be pointed out, however, that this setting of levels should be done 

 on the residual sample of gas, i. e., nitrogen, rather than on the sample 

 of gas to be analyzed. If this is not done, the first measurement of the 

 sample to be analyzed will be incorrect. After all of the connecting 

 tubes have been filled with nitrogen, the nitrogen is expelled from the 

 burette into the open air. 



The drawing of the sample may take place either by the washing 

 method or by forcing mercury out through the connections to the 



