TRANSACTIONS OF SECTION B. 



325 



4. Description of a Glass Burette for Collecting, Measuring, and Discharg- 

 ing Gas over Mercury. By Philip Braham, F.C.S. 



The burette consists of a divided glass tube opeu at both ends, the lower end, A, 

 having; a lip and the upper end being covered 

 with a loosely-fitting boxwood cap. 



A piston, B, formed of a disc of india- 

 rubber between two plates of steel, connected 

 to a steel rod, c, is fitted into the tube. 



To fill the burette, the piston is depressed 

 below the lower end until some of the mer- 

 cury escapes above it, and on drawing it up 

 auy portion of the tube can be filled. 



When the gas has been delivered its 

 measurements may easily be made by lower- 

 ing the piston till the mercury inside is level 

 with that out, and the content read off. By 

 placing the lip under a eaudiometer, on fur- 

 ther depression of the piston any required 

 amounts of gas may be delivered for analysis, 

 the clamp e being fixed to stop the piston 

 when the required amount is discharged. 

 The clamp D is used to prevent the piston 

 descending when the instrument is full of 

 mercury. 



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