8 4 



ANDRAL AND GAVARRET S APPARATUS. 



2. By Weight. A large quantity of the mixture of gases which has to be investigated is made 

 to pass through a Liebigs bulb filled with caustic potash. The potash apparatus having been 

 carefully weighed beforehand, the increase of weight indicates the amount of C0 2 which has 

 been taken up by the potash from the air passed through it. 



3. By Titration. A large volume of the air to be investigated is conducted through a known 

 volume of a solution of barium hydrate. The C0 2 unites with the barium and forms barium 

 carbonate. The fluid is neutralised with a standard solution of oxalic acid, and the more barium 

 that has united with the C0 2 the smaller will be the amount of oxalic acid used, and vice versd. 



II. Estimation of Oxygen. According to volume (a) By the union of the with potassium 



pyrogallate. The same 











J, 



n 



Fig. 143. 

 Apparatus of Andral and Gavarret for collecting the expired air. 



fl 



procedure is adopted 

 as for the estimation 

 of C0 2 , only the flask, 

 ft, is filled with the 

 pyrogallate solution in- 

 stead of potash, (b) 

 By explosion in an 

 eudiometer (see Blood- 

 Gases, 35). 



III. Estimation of 

 Watery Vapour. The 

 air to be investigated is 

 passed through a bulb 

 containing concentrated 

 sutyhuric acid, or 

 through a tube filled 

 with pieces of calcium 

 chloHde. The amount 

 of water is directly in- 

 dicated by the increase 

 of weight. 



122. METHODS OF 

 INVESTIGATION. I. 

 Collecting the Expired 



Air. (1) The air ex- 

 pired may be collected 

 in the cylinder of the 

 C, spirometer, which is 



large cylinder to collect the air expired ; P, weight to balance cylin- suspended in concen- 



der ; a, b, two Midler's valves ; M, mouthpiece. II. Anthracometer trated salt solution to 



ofVierordt. avoid the absorption 



ofCO 2 (108). 



Andral and Gavarret's Apparatus. The operator breathed several times into a capacious 

 cylinder (fig. 143). A. mouthpiece (M) was placed air-tight over the mouth while the nostrils 

 were closed. The direction of the respiratory current was regulated by two so-called "Muller's 

 Valves " (mercurial), (a and b). With every inspiration the bottle or valve, a (filled below with 

 Hg and hermetically closed above), permits the air inspired to pass to the lungs during every 

 expiration the expired air can pass only through b to the collecting-cylinder C. 



(2) If the gases given off by the skin are to be collected, a limb, or whatever part is to be 

 investigated, is secured in a closed vessel, and the gases so obtained are analysed. 



II. The most important apparatus for this purpose are those of (a) Scharling (fig. 144), 

 which consists of a closed box, A, of sufficient size to contain a man. It is provided with an 

 inlet 2 and outlet b. The latter is connected with an aspirator, C, a large barrel filled with 

 water. When the stop-cock, h, is opened and the water flows out of the barrel, fresh air will 

 rush in continuously into the box, A, and the air mixed with the expired gases will be drawn 

 towards C. A Liebig's bulb, d, filled with caustic potash, is connected with the entrance tube, 

 c, through which the in-going air must pass, whereby it is completely deprived of C0 2 , so that 

 the person experimented on is supplied with air free from C0 2 . The air passing out by the 

 exit tube, b, has to pass first through e, where it gives up its watery vapour to sulphuric acid, 

 whereby the amount of watery vapour is estimated by the increase of the weight of the 

 apparatus, e. Afterwards the air passes through a bulb, f. containing caustic potash, which 

 absorbs all the C0 2 , while the tube, g, filled with sulphuric acid, absorbs any watery vapour 

 that may come from/. The increase in weight of /and g indicates the amount of C0 2 . The 

 total volume of air used is known from the capacity of C. 



(b) Regnault and Reiset's Apparatus is more complicated, and is used when it is necessary 

 to keep animals for some time under observation in a bell-jar. It consists of a globe, R, in 



