HALDANE GAS-ANALYSIS APPARATUS. 73 



burette, A, can be introduced into the potash pipette E or into the 

 potassium pyrogallate pipette L, at will, but not simultaneously into 

 both. Level marks on the two pipettes show the height to which the 

 solutions are drawn. 



The potassium pyrogallate is made by dissolving 10 gm. of pyro- 

 gallic acid in 100 c.c. of a nearly saturated solution of caustic potash. 

 The specific gravity of the caustic potash should be 1.55. The potas- 

 sium pyrogallate is kept in a closed bottle and should be prepared some 

 time before it is to be used. 



To compensate for changes in temperature and pressure, another 

 tube, K, of the same size and construction as the burette A, and con- 

 taining a few cubic centimeters of water is inserted in the water- 

 jacket B, parallel with the burette, and is connected to the potash 

 pipette E through a three-way stopcock J. When the three-way stop- 

 cock J is opened to the outside air, the level on the tube below the 

 stopcock and the level on the potash pipette E may be set at atmos- 

 pheric pressure by raising or lowering the bulb 7, the potash solution 

 acting as a manometer. After the level has been set, the stopcock J 

 is closed to the outside air. The air on each side of the potash solution 

 is then at the same pressure. 



In the original Haldane apparatus the mercury in the burette A is 

 raised or lowered by means of the long cylindrical leveling bulb, con- 

 structed of tubing similar to that used for the burette. In this labora- 

 tory it was found somewhat difficult to use this type of leveling bulb, 

 owing to the fact that occasionally the clamp which held it did not grip 

 the tube firmly enough to prevent its slipping. When this occurred 

 the potash or the potassium pyrogallate solution would be drawn over 

 into the burette, causing considerable inconvenience. The leveling 

 bulb has, therefore, been so modified that the manipulation is much 

 easier. At the bottom of the burette A is placed a piece of rubber 

 tubing with a metal tube, 0, surrounding it. Inside the latter is a 

 flat metal piece which presses against the rubber tubing and can be 

 moved by means of a fine adjusting screw, P. A common glass stop- 

 cock, Q, is placed between and the leveling bulb D and connected 

 to the latter by means of rubber tubing. In manipulation, the glass 

 leveling bulb D is raised or lowered until the mercury is nearly at the 

 point desired. The stopcock Q is then closed and the final adjustment 

 of the mercury level in the burette, A, is made by the fine adjustment 

 screw P, which alters the pressure on the rubber tube. No accidents 

 of the character described above have occurred since this was adopted. 



The original Haldane apparatus contains a combustion pipette for 

 the oxidation of carbon monoxide or methane. In this laboratory 

 there has been no occasion for using this pipette for the purpose 

 designed. It has therefore been utilized to advantage in experimenting 

 with phosphorus as an absorbent for oxygen. The upper of the two 

 right-angle stopcocks, G, leads to the combustion pipette R on the 



