A CONVENIENT FORM OF BURETTE CREIGHTON. I I / 



through which the water-jacket be filled or emptied, or through 

 which water at a constant temperature can be circulated. 



The lower end of Dl, and D2, and the lov/er ends of thr 

 small and large arms of the burette are joind by heavy rubbee 

 tubing to the three-arm tube X, the horizontal portion of which 

 is joined by two meters of rubber pressure tubing to a reservoir 

 containing mercury. 



The absorption pipettes are connected to the upper end 

 of the burette in the usual way. The rubber connections are, 

 however, enclosed in mercury to prevent leaks. It is also ad- 

 visable to employ for L a stop-cock with a mercury seal. 



In order to measure a given volume of gas enclosed in the 

 burette, the stop-cock LI is closed, the stop-cock L2 opened 

 and the reservoir containing the confining liquid raised or 

 lowered, until the level of mercury the in the larger arm of the 

 burette is brought to one of the marks between two of the bulbs 

 Bl. If the volume of gas is between 95 and lOOcc, the first 

 small bulb is filled with mercury; if the volume is between 90 

 and 95 cc. the first two small bulbs are filled with mercury 

 and so on The stop-cock L2 is then closed and the stop-cock 

 LI opened, and the fraction of 5cc contained in P measured by 

 bringing the mercury in P, Dl and D2 to the same level. This 

 is readily accomplished by getting the mercury meniscus in 

 each of the three tubes in a line, one behind the other When 

 this is done, the stop cock LI is closed and the volume of gas 

 read. It is necessary, of course, to make corrections for changes 

 temperature and pressure which occur during analysis. 



With this particular burette it is only possible to measure gas. 

 volumes which are more than 70 cc. and not more than 100 cc. 

 The writer has used this burette to determine the carbon- 

 dioxide, oxygen and carbonmonoxide in more than one hundred 

 samples of air, in laboratories and large industrial plants. In a 

 number of instances where small quantities (0.02 to 0.04 per 

 cent.) of carbonmonoxide were found present in the air, sub- 

 sequent investigation showed its presence to be due to small 

 leaks in the illuminating gas lines and connections. 



The Chemical Laboratory, 

 March 2nd. 1920. 



