396 On an Apparatus for Gas-analysis 



alkaline 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 

 stopcocks c and b being shut. The stopcock d is now opened 

 and a turned the reverse way to what it is in Fig. 2 that is, 

 with the side communication fly 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 capillary driven into m. The hydrogen 

 is now passed over into the eudiometer and exploded, the 

 measurements being made as described. 



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, 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 tin- 

 apparatus 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. 

 Communication with the reservoir can be made or interrupted 

 by the stopcock G. One of the tubes, A, is furnished with 

 two platinum electrodes ; the other, B, has but one. Delivery- 



