116 METHODS FOR THE ANALYSIS OF BLOOD 



stopcocks 3 and 8. (The stopcock 8 is double-bored, so that 

 the tube leading from the burette can be brought into connection 

 with either 9 or 12.) The control burette 10 is also in connection 

 with this bulb through the manometer tube 11. (This tube also 

 has a three-way stopcock 19, so that it may be opened to the out- 

 side.) Any variation in temperature which may occur during the 

 analysis will cause the level of the alkaline solution in the manom- 

 eter to change. 



When final readings of the shrinkage of volume are made, 

 the level of the caustic solution is returned to the level of that in 

 the manometer. By so doing any error due to temperature changes 

 is avoided, since change in temperature must be equal in the two 

 burettes. 



The absorption bulb 12 for oxygen is filled with a solution 

 made by dissolving 10 gms. of pyrogallic acid in 100 c.c. of a 

 nearly saturated KOH solution. The specific gravity of the KOH 

 should be 1.55, which is obtained approximately by dissolving 

 the sticks (pure by alcohol) in an equal weight of water. The 

 mark 13 on the stem of the bulb indicates the level at which the 

 solution should stand. Enough pyrogallate solution is introduced 

 through tube 15 to fill bulbs 12 and 14 two-thirds full. Then 

 pyrogallate solution is poured into tube 16 until the difference 

 in level of the fluids is sufficient to produce enough pressure to 

 raise the level of the pyrogallate solution in 12 to the level 13 on 

 the stem. Stopcock 8 must be open during this procedure. It 

 may be necessary to add or take away a little pyrogallate solution 

 through 15 to attain the above level. 



Care must be taken to allow for complete absorption of oxygen 

 from the air that is entrapped between 14 and 16 before an analysis 

 is made; otherwise changes will be produced in the level of the 

 pyrogallate solution. The air in the capillary tubing connecting the 

 burettes with the absorption bulbs must also be freed of CO2 and C>2. 

 This can be accomplished by making a dummy analysis of atmos- 

 pheric air before the real analysis. Great care must be taken to 

 have atmospheric pressure in all the tubes at the start of the 

 analysis. This is accomplished by opening the stopcock in the 

 burette first to atmospheric air and then to the absorption bulbs, 

 until no further change in the level of the fluids in the stems of 

 the absorption bulbs occurs. This level is then marked and used 

 as the standard, A small amount of water in the burette over 



