Comparative Air-Analyses 



95 



1911. A further change was made at this time which was due to the fact 

 that at the end of an analysis the potassium pyrogallate was in contact 

 with pure nitrogen in the capillary tube inside the chamber, while the 

 reagent in the outer part of the reagent chamber was in contact with air. 

 This was remedied by the attachment of a double bulb to the tube through 

 which the chamber is filled. This double bulb provided a seal, one bulb 

 containing water and the other air. When a sample of air was forced 

 into the pyrogallate vessel, the reagent, rising on the outside of the inner 

 tube, forced the gas above it into the first bulb, thereby expelling the 

 water which it contained into the second bulb. 



The modified routine adopted on February 15, 1911, was as follows: 

 After absorbing the carbon dioxide, the air was sent back and forth into 

 the potassium pyrogallate five times, being left there each time 10 seconds. 

 The first reading was then taken. Following this the air was again sent 

 into the potassium pyrogallate for 10 seconds and a second reading taken. 

 This procedure was carried on until the readings were essentially constant. 

 About this time a change was also made in the carbon-dioxide routine. 

 As it appeared unnecessary to make two readings of this factor, the first 

 reading was omitted, although the procedure for transfer of air to and 

 from the potassium-hydroxide pipette was not altered in any way. With 

 this routine, therefore, the air was passed from the measuring pipette into 

 the potassium pyrogallate a maximum of eight times. A sample analysis 

 made with the third routine is given in table 55. 



Table 55. Results obtained on a sample of outdoor air with third 

 routine, February 20, 1911, J^ 25 m p. m. 



This routine was followed for but two days in the regular air-analyses; 

 the few results are given in table 56. During the period from February 

 16 to March 10 the cylinder air was likewise more or less continually 

 analyzed, the third routine being used. (See table 57.) 



Table 56. Analyses of outdoor air made at the Nutrition Laboratory. Series 3. 



