A CONVENIENT FORM OF BURETTE CREIGHTON. 115 



A Convenient Form of Burette for Exact Gas Analysis. 

 By Henry Jermain Maude Creighton, D. Sc, x^ssist- 

 ant Professor of Chemistry, Swarthmore College, Swarth- 

 more, Penn., U. S. A. 



(Read 10 May. 1920) 



A large number of gas burettes for various kinds of analysis 

 is described in the chemical literature and in the catalogues of 

 chemical apparatus. With most of these burettes, which have 

 a volume of 1 00 or I 50 cc. and are graduated to read to 0. 1 or 

 0.2 cc, it is not possible to measure differences in volume with 

 an accuracy of more than 0.1 or 0.2 per cent., an accuracy 

 sufficient for many purposes. Since in some kinds of work a 

 greater accuracy is highly desirable, the writer proposes to de- 

 scribe a type of burette which has he designed and had specially 

 made for determining differences in gaseous volumes with a 

 accuracy of about 0.02 per cent. 



This burette (Figure 1) consists of a measuring tube, P, and 

 a reservoir-tube, A, joined together at the top by a capillary 

 tube to which is connected a stop-cock, L, and closed at the 

 bottom ends by the stop-cocks, LI and L2. The tube A is 

 made up of five small bulbs, Bl, each holding 5.00 cc. between 

 the marks on the constricted portions on either side of the bulb, 

 and a large bulb, B2. The volume of the bulb B2 and the cap- 

 illary tube between the stop-cock L amd the mark M on the 

 upper portion of the tube P is 70 cc. The arm P, consisting of 

 a thick-walled tube with an internal diameter of three mill- 

 imeters, has a volume of 5.00 cc. getween the marks M and N. 

 This portion of P is graduated throughout its entire length and 

 each division reads 0.01 cc. 



As small variations in temperature during analysis produce 

 changes in the volume of gas amounting to several hun- 

 dredths of a cubic centimeters, the burette is enclosed in a water- 

 jacket, K, along with a thermometer, T, reading to tenths of a 

 tenth of a degree. The water-jacket has a diameter of 85, 

 cm., and is closed at the ends by the rubber stoppers Rl . There 

 are also enclosed in the water-jacket two leveling tubes, D! and 

 D2, which have approximately the same diameter as the small 

 arm, P. of the burette. These two tubes are joined together 

 at the bottom outside the water-jacket. Each of the rubber 

 stoppers, Rl, has a small opening (not shown in the Figure) 



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