A2}i)aratuf^ for Rapid Gm- Analysis.. 379 



der under pressure. Having added tlie pro])er quantity of oxygen 

 (about equal in volume to the gas used),* the correct volume of 

 the mixture thus obtained is read ofE in tlie same manner as that 

 of the original gas. But before the final reading is made, the 

 burette is removed from the stand, and by a few movements 

 from vertical to horizontal positions, the gases are mixed, and 

 any oxygen that collects in the tube, E, is removed to the bulk 

 of the gases in the nj^per part of the burette. Having taken 

 the final reading of the mixture, the upper part of the tube is 

 tapped slightly to dislodge any water adhering to the platinum 

 wires, and the spark from an induction coil is passed between 

 them, the aspirator-bottle being below the level of F, in order 

 to expand the mixture. A sharp click is now heard, and the 

 tube is allowed to stand so that the heat of the explosion may pass 

 away before I'eading the contraction. When the tube is cool, 

 the ]"eading is taken by lifting the aspirator-bottle as before. 

 'J'his reading gives the contraction, and. by removing the bent 

 tube and replacing the cylindrical funnel, A, the carbonic acid 

 resulting from the ex]:»losion may be absorbed with potassic hy- 

 drate, as in the absorption-apparatus, the readings always being 

 taken after adjusting the levels of the liquids in the burette and 

 the aspirator-bottle. 



When removing the bent tul)e and attaching the cylindrical 

 funnel, cai'e should be tak<n that the air in the ctipillary tube 

 of the stop cock is removed. This is accomplished by attaching 

 the funnel, putting into it a little potash solution, and then in- 

 serting a piece of thin copper wire into the capillary tube of the 

 stop-cock ; by this means the air-bubbles are readily removed. 

 Like the absorption-apparatus previously described, this explo- 

 sion-buj'ette is intended for rapid work where some accuracy is 

 sacrificed to the saving of time. It has the great advantage that 

 the explosion can be made over water — the long piece of rubber 

 tubino- acting as a cushion to the shock. I have used this 

 burette for over a year, and with the most satisfactory results. 



* If the gas mixture contains little or no nitrogen, it is better to add lialf 

 the volume of oxygen and one volume of atmospheric air, to moderate the 

 force of the explosion. 



