FREE AND HOUND CO^ 553 



often as necessary. Rotation for (it Inisl 1 minute is necessary after each 

 addition of acid. 



Titration value for 0-5 c.c. [)lasma = 0-77 c.c. N/50H('l, 

 i.e. Alkali reserve of ,, ,, = 0-77 c.c. N/SONaHCOa 



100 c.c. ,, = 154 c.c. 



= 3-08 N 



= 3-08 X 224 c.c. CO2, 

 i.e. 68-99 volumes per cent, of CO2 are bound as bicarbonate in the plasma. 



A sharper end-])oint is obtained liy the use of ])henol sulphonephthalein as 

 indicator. In this case the standard phosphate solutions are made of pH 7-2 

 to correct the protein error. 



(c) Alkali reserve by Van Slyke's method. The Van Slyke ap])aratus is 

 illustrated in Fig. 111. It consists essentially of a 50 c.c. pipette with three- 

 way sto})COcks (e and/) at top and bottom, and a 1 c.c. scale on the upper 

 stem, divided into 0-02 c.c. divisions. The body of the apparatus is connected 

 through heavy walled rubber tubing with a levelling bulb filled with mercury. 

 The whole apparatus is supported on a stand so that, without unclamping, the 

 pipette may be rotated round a central axis. The stopcocks are lubricated 

 with a rubber-vaseline mixture and may be held in place by strong rubber 

 bands. 



Prelim innry preparation. Open taps e and / and fill the entire apparatus 

 with mercury by raising the levelling bulb, allowing some mercury to run into 



/l^oi/r/z-p/ecc. 



S/IMPL/A/G TUBE. 



riG. 112. — Alveolar air collecting tube. 



a and into h. Shut e, and lower the levelling bulb till the mercury falls half- 

 way down c and d. The bulb is then slowly raised. If the apparatus is gas- 

 free, a sharp click will be heard when the mercury strikes the upper stopcock. 

 If a gas cushion is present, open e, and force the gas out, and repeat the evacua- 

 tion process, opening/ alternately to c and d. 



Determination. (1) Solutions refpiired. It is convenient to have four 

 dropping bottles with ground in ])ipettes and rubber teats containing 

 (a) 5 per cent. H2SO4, (6) 1 per cent, carbonate-free NII3 water, (c) caprylic 

 alcohol and [d) distilled water. The carbonate-free ammonia is prepared 

 by adding a small amount of sat. barium hydrate solution to ordinary 

 ammonia solution. The barium carbonate is filtered of¥, and the excess of 

 barium remaining is precipitated with a little {NH4)2S04. 



(2) Plasma. An ordinary centrifuge tube is fitted out with rubber cork 

 and glass tubes just like a wash-bottle. The longer tube bears at its upper 

 end a hypodermic needle. The whole apparatus — glass, tubes and needle — 

 is washed out with a saturated solution of neutral potassium oxalate. (Van 

 Slyke and Cullen point out that it is desirable that the subject should avoid 

 vigorous muscular exertion for at least an hour before the blood is drawn. 

 It is also best to avoid stasis, or when stasis is unavoidable the ligature should 

 be released as soon as the vein is entered. In tliis case, the first sample of 

 blood should be neglected.) The blood should run into the tube without 

 suction. By a gentle rotary motion, mix the blood with the finely crystallised 

 oxalate left adhering to the walls of the vessel, and centrifuge at once. The 



