V. PETf SNKOFER'S RESPIRATION APPARATUS. 



253 



any trace of C0 2 , a vessel containing potash (Fig. 112, C0 2 ) is placed in the course 

 of the tube. The vessel for measuring the is emptied towards R, through a 

 solution of calcium chloride from a large pan (Ca C1 2 ) provided with large flasks. 

 Two tubes, d and e, lead from R, and are united by caoutchouc tubes with the 

 potash bulbs (KOH, Ko/i), which can be raised or depressed alternately by means 

 of the beam, W. In this way they aspirate alternately the air from R, and the 

 caustic potash absorbs the C0 2 . The increase of weight of these flasks after the 

 experiment indicates the amount of C0 2 expired. The manometer, f, shows 

 whether there is a difference of the pressure outside and inside the globe, R. 



(c.) V. Pettenkofer has invented the most complete apparatus (Fig. 113). It 

 consists of a chamber, Z, with metallic walls, and provided with a door and a 

 window. At a is an opening for the admission of air, while a large double suction- 

 pump, P P! (driven by means of a steam-engine) continually renews the air within 

 the chamber. The air passes into a vessel, 6, filled with pumice-stone saturated 

 with sulphuric acid, in which it is dried; it then passes through a large gas-meter, 

 c, which measures the total amount of the air passing through it. 



After the air is measured, it is emptied outwards by means of the pump, P Pj. 

 From the chief exit tube, x, of the chamber, provided with a small manometer, q, a 

 narrow laterally placed tube, n, passes, conducting a small secondary stream, 



Fig. 113. 



Respiration Apparatus of v. Pettenkofer Z, chamber for person experimented on ; 

 x, exit tube with manometer, q; b, vessel with sulphuric acid; C, gas-meter; 

 PPi, pump; n, secondary current, with, k, bulb; MM 1} suction apparatus; 

 u, gas-meter; N, stream for investigating air before it enters Z. 



which is chemically investigated. This current passes through the suction' 

 apparatus, M MI (constructed on the principle of Miiller's mercurial valve, and 

 driven by a steam-engine). Before reaching this apparatus, the air passes through 

 the bulb, K, filled with sulphuric acid, whose increase in weight indicates the 

 amount of watery vapour. After passing through M MI, it goes through the 



