420 



ILLUSTRATIVE EXPERIMENTS 



50 c.c. mark. Close / and replace the bulb on the upper ring. Slacken 

 the milled head of the screw that controls the central swivel. Holding the 

 pipette at the bulb with the right hand and gathering up the loose rubber 

 tubing with the left, rotate the bulb through 180 some 15 times. Set 

 vertically and tighten the milled head. Lower reservoir and, with / open 

 to d, rapidly empty the water solution into d without however allowing 

 any of the gas to follow it. Now open /to c and, by raising the reservoir, 

 fill the body of the pipette with clean mercury. Hold the reservoir in such 

 a position that pressure inside the reservoir is atmospheric and rapidly take 

 a reading. If thought desirable, re-extraction may be carried out. 



FIG. 81. Van Slyke Micro Apparatus. 



Cleaning. Lower the reservoir and run most of the mercury back 

 through c. Open ftod and, by raising the reservoir, run the water back 

 into the pipette. Open e to a and force the fluid out into a collecting jar. 

 The apparatus is now ready for another determination. 



Micro apparatus (Fig. 81). This apparatus is easier to manipulate, and 

 as water, etc., never enters the gas pipette, it is easily kept clean. The 

 different parts are in the same relative proportions as the corresponding 

 parts of the larger apparatus. Each division of 0-002 c.c. on the smaller 

 corresponds to 0-01 c.c. on the larger. 



(1) It is advisable to mark the course of the canals with pencil on the 

 butt end of the tap d. 



