9 



15. Ki^vi't/ carbon, test, Copper bath, test-lubes(12) ; 

 graduated tubes (2). Price, is*. (\d. 



1876. Exhibited by J. Ormc fy Co. 



1(5. Stead-Kobson's apparatus for the analysis )t' blast 

 furnace and other gases, with photograph of thu ap- 

 paratus. Price, 4/. 10s. 



1886. Exhibited by J. Crosby llobson. 



Description of working in testing blast furnace gases. 

 Having raised the mercury reservoir above the level of the 

 capillary tubes, the cock at the top right-hand end of the appa- 

 ratus is opened, and the mercury forced to the extremity of the 

 glass tube seen at the top right-hand end of the apparatus. The 

 indiarubber tube which is connected with the gas to be tested 

 is slipped over the open end. By opening the stopcock mentioned 

 above and lowering the mercury reservoir a sample of gas is 

 rapidly transferred into the measuring tube ; and when a sufficient 

 quantity, namely, about 150 mm., has passed into it, the stop- 

 cock is shut off. We now raise the mercury reservoir until the 

 mercury in the measuring tube and the one next to it is at the 

 same level, which point is ascertained by the spirit level fixed 

 in a wooden frame in front of the tubes, and sliding up and 

 down in guides. After carefully noting down the volume of gas 

 enclosed, the mercury reservoir must be raised and the left-hand 

 stopcock on the top of the apparatus opened ; and the gas forced 

 into the chamber containing potash, i.e., one of the vessels on 

 the left of the apparatus. In about t\vo or three minutes the 

 carbonic acid is completely removed and by lowering the mercury 

 reservoir and opening the left-hand stopcock, the gas may be 

 returned to the measuring tube, where its volume is again care- 

 fully noted. The difference between the first and the second 

 volumes is the amount of carbonic acid absorbed. Before, how- 

 ever, the gas is drawn back from the laboratory vessel, the minute 

 amount of gas which remains in the capillary tube on the right, 

 which escapes measurement, is expelled by opening the right- 

 hand stopcock. Oxygen gas is now connected to the end of 

 this tube, and a sufficient quantity of it drawn into the measuring 

 tube. In order to thoroughly mix the two gases, they are forced 

 into the potash laboratory and again drawn into the measuring 

 tube, and the exact volume carefully noted. An electric spark 

 is now passed through the mixture, and the contracted volume, 

 after cooling, is noted. The resulting carbonic acid is absorbed 

 again by transferring the ignited gases into the potash chamber, 

 and after finally obtaining it in the measuring tube the remaining 

 volume is carefully noted. 



As the gases remain throughout saturated with aqueous vapour, 

 it is not necessary to make any correction for its tension. 



The calculations are simple and easily made. 

 a = corrected volume of gas taken. 



