Mr. J. \ . Buchanan on an Apparatus for Gas-analysis. 5 



lated by raising or depressing p, and the gas allowed to pass 

 over into q until the potash solution just touches the lower sur- 

 face of the stopcock a, which, being open, has the position shown 

 in fig. 3. The position of a is now shifted to that shown in 

 fig. 2, when the potash solution is eliminated. The position of 

 a is now brought back to that represented in fig. 3, and the gas 

 remaining in the capillary swept out by mercury and the volume 

 measured as above described. 



If the oxygen is to be determined by absorption, the manipu- 

 lations are exactly the same as in the case of carbonic acid, alka- 

 line pyrogallic acid being used instead of caustic potash. If it is 

 to be determined eudiometrically, then, after the carbonic acid 

 has been absorbed, the gas remains in the eudiometer, the stop- 

 cocks c and b being shut. The stopcock dis now opened and a 

 turned the reverse way to what it is in fig. 2 — that is, with the 

 side communication /3 y communicating with the capillary above 

 a. The capillary is then emptied of mercury and the hydrogen- 

 evolving apparatus connected with y by means of an india-rubber 

 tube, and the hydrogen allowed to stream through a, d, e until 

 all air is swept out ; the stopcock d is then closed and a brought 

 back to its position in fig. 2, when the gas enters m. When 

 enough hydrogen has passed in, a is brought to its position in 

 fig. 3 and the hydrogen-apparatus dispensed with. Mercury is 

 then poured into e, and d opened and the hydrogen in the capil- 

 lary driven into m. The hydrogen is now passed over into the 

 eudiometer and exploded, the measurements being made as de- 

 scribed. 



When the analysis is finished the mercury 'is emptied out of 

 the tubes, the parts A and B bolted each into its own side of the 

 box, the screws x, w, x being lodged in the nuts w, w, w let into 

 the board A. The box when closed measures 0*48 metre by 

 0*22 metre by 0*22 metre, outside, and is easily portable. 

 Of course the apparatus is not meant exclusively for work on 

 board ship, where indeed attempts at gas-analysis should be 

 avoided, as at the very best the results must be very uncertain ; 

 but it makes a compact laboratory apparatus and is economical 

 in mercury. 



For the preparation of the electrolytic gases, either separate or 

 mixed, in a way convenient for gas-analysis, I have had the ap- 

 paratus represented in fig. 4 constructed. It is of the well-known 

 lecture-apparatus form, and consists of two tubes, A and B, 

 united at their lower extremities by the short tube C, which 

 connects them at the same time by means of the tube D with 

 the reservoir E. At their upper extremities A and B terminate 

 in capillary tubes furnished with stopcocks, F, F. Communica- 

 tion with the reservoir can be made or interrupted by the stop- 



