60 



passing on through fresher and fresher material, gaining heat 

 from that which has been in some time, and giving it up again 

 to the material which has been lately charged in, escaping 

 finally, through the flue in the last chamber. It will thus be 

 seen that material is cooled down by the entering air before 

 removing, and that the working is continuous. The iron door is 

 moved round the kiln from left to right, following the course of 

 the air, the flue, which is left open, being the one immediately to 

 the left of the door. 



B. ANALYTICAL APPARATUS. 



195. Bunte's gas burette for the analysis of furnace 

 gases. Price 15s. 



1886. Exhibited by Townson fy Mercer. 



The burette is filled with water from below until it begins to 

 enter the funnel at the top. The side opening of the three-way 

 cock at the top is now put in connexion with the gas to be 

 analysed ; the gas is allowed to enter until the water passes 

 below the zero mark, and the upper tap is closed. Water is now 

 forced in from below till it reaches the zero mark ; the upper 

 cock is opened momentarily so that the excess of gas escapes 

 through the water filled to the mark on the upper funnel, and then 

 the tap is closed, so that in the burette there is now 100 c.c.'s of 

 gas at a pressure equal to the height of water in the funnel added 

 to the atmospheric pressure. In order to dissolve any constituent 

 of the gas a suitable absorbing liquid is run in, thus : the water in 

 the burette is nearly all sucked out through the bottom tap, and 

 the tap closed, and the end of the burette introduced into the 

 absorbing liquid, which will rise into the burette nearly up to 

 the zero mark on opening the tap again; the burette is well 

 shaken, and the tip again introduced into the absorbing liquid, 

 and when the tap is opened more will enter. The tap is now 

 closed, and the shaking repeated. The gas is again put under 

 proper pressure by running water in from the funnel above, and 

 filling the funnel up to the mark whilst the tap is open. The 

 amount of gas absorbed is then read off, and the number of c.c.'s 

 gives the per-centage of the absorbed gas in the mixture. 



196. Orsat's apparatus for the technical analysis of 

 gases. 



E. 66. 1888. Made by 0. Gerhardt, Bonn. 



The graduated measuring tube contains from the zero mark 

 at its bottom to the upper capillary exactly 100 c.c., and is 

 graduated in ^ c.c. up to 50 c.c., and above that in -^ c.c. The 

 burette is surrounded by a water jacket so as to withdraw the gas 

 in it from the influence of changes in the temperature of the 

 external air. The jacket is closed at the top and bottom by india- 

 rubber stoppers, and is provided with a white background of 



