stopper coincides with one through the burette tube, air is 

 admitted into the burette, and allows the liquid to run out 

 through a glass stopcock in a side-arm near the bottom of the 

 graduated tube. 



32. Stand for six burettes on round porcelain foot with 

 polished brass rod and gun-metal mounts. Price 2,1. 2s. 



1886. Exhibited by Townson fy Mercer. 



33. Burette stands : 



Stand for eight burettes. Price 1.5s. 6d. Dr. Percy's 



form. Price 7s. 6d. 

 1876 and 1886. Exhibited by J. Orme $ Go. 



34. Hempel's explosion pipette. Price 13s. 



1886. Exhibited by Townson Sf Mercer. 



The bulbs on the right limb are of 100 c.c. and 50 c.c. 

 capacity respectively, and the bulb on the left limb is of about 

 160 c.c. capacity. About 160 c.c.'s of a 5 per cent, solution of 

 pure potash is introduced into the pipette. Then with both 

 pinch-cocks open the liquid is blown from the left limb up to 

 a mark on the right limb between the bulbs, and the cocks are 

 then closed so that there has been a known volume of air at 

 atmospheric pressure introduced, which is necessary for explosion 

 by burning. Then connect top of pipette to a burette containing 

 gas to analyse and introduce a known quantity. The explosive 

 gas necessary for the analysis is produced directly by the 

 electrolysis of the potash, and the liquid is depressed into the 

 left limb. Agitate the apparatus so as to mix the gas before 

 explosion. All the potash is then sucked to top of the left bulb, 

 and the cocks closed, and the spark passed. The gas is agitated 

 with the potash and re-measured. 



35. Hempers gas pipette, two bulbs. Price 9s. 6d. 

 1886. Exhibited by Townson fy Mercer. 



The lower bulb of the pipette is filled with the absorbing 

 liquid, and the capillary tube is connected with a gas burette, 

 which contains usually about 100 c.c.'s of gas, which is forced 

 from the burette into the lower bulb, thus displacing most of the 

 absorbing liquid into the higher bulb. After a few minutes the 

 gas is sucked back into the burette, and its volume measured, 

 and the amount which has been absorbed thus determined. 



36. Enamelled iron-digester, with five holes in cover to 

 receive evaporating basins, test-tubes, &c. Price 6s. 6d. 

 Porcelain rings ; a set of 7 rings internetting for 

 covering evaporating baths, &c. Price 3s. 6d. the set. 



1886. Exhibited by Townson 8f Mercer. 



