v. PETTENKOFER'S RESPIRATION APPARATUS. 



253 



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

 of the tube. The vessel for measuring the O 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/t), which can be raised or depressed alternately by means 

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

 caustic potash absorbs the COg. 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 PJ (driven by means of a steam-engine) continually renews the air within 

 the chamber. The air passes into a vessel, b, filled w r ith 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 M! (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 MMi, it goes through the 



