GENERAL DESCRIPTION OF RESPIRATION APPARATUS. 65 



caution must be taken. At no point in the whole apparatus is it necessary 

 to be more careful than with the couplings which connect the various 

 absorber systems with each other and with the valves; for these couplings 

 are opened and closed once every hour or two and hence are subject to 

 considerable strain at the different points. If they are not tight the 

 experiment is a failure so far as the determination of oxygen is concerned. 

 For the various parts of the absorber system we have relied upon the ori- 

 ginal type of couplings used in the earlier apparatus. A rubber gasket is 

 placed between the male and female part of the coupling and the closure 

 can be made very tight. In fact, after the absorbers are coupled in place 

 they are invariably subjected to severe tests to prove tightness. 



For connecting the piping between the calorimeter and the absorption 

 system we use ordinary one-inch hose-couplings, firmly set up by means 

 of a wrench and disturbed only when necessary to change from one calo- 

 rimeter chamber to another. 



ABSORBER TABLE. 



The purifying apparatus for the air-current is compactly and conven- 

 iently placed on a solidly constructed table which can be moved about the 

 laboratory at will. The special form of caster on the bottom of the posts 

 of the table permits its movement about the laboratory at will and by 

 screwing down the hand screws the table can be firmly fixed to the floor. 



The details of the table are shown in fig. 30. (See also fig. 4, page 4.) 

 The air coming from the calorimeter passes in the direction of the down- 

 ward arrow through a J-inch pipe into the blower, which is immersed in 

 oil in an iron box F. The blower is driven by an electric motor fastened 

 to a small shelf at the left of the table. The air leaving the blower ascends 

 in the direction of the arrow to the valve system H, where it can be directed 

 into one of the two parallel sets of purifiers; after it passes through these 

 purifiers (sulphuric-acid vessel 2, potash-lime container K, and sulphuric- 

 acid vessel 1) it goes through the sodium-bicarbonate can G to a duplicate 

 valve system on top of the table. From there it passes through a pipe along 

 the top of the table and rises in the vertical pipe to the hose connection 

 which is coupled with the calorimeter chamber. 



The electric motor is provided with a snap-switch on one of the posts of 

 the table and a regulating rheostat which permits variations in the speed 

 of the motor and consequently in the ventilation produced by the blower. 

 The blower is well oiled, and as oil is gradually carried in with the air, a 

 small pet-cock at the bottom of the T following the blower allows any 

 accumulated oil to be drawn away from time to time. The air entering 

 the valve system at H enters through a cross, two arms of which connect 

 with two " white star " valves. The upper part of the cross is connected 



