220 MICROMETRY AND BLOOD PREPARATIONS 



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neutralize acids. The carbonic acid is taken up by the bicarbonate 

 of the blood and gotten rid of as CO 2 by the lungs, without any loss of 

 sodium bicarbonate. 



Other metabolic acids, however, cause a loss of sodium bicarbonate (and along 

 with this the other blood alkalis) so that the determination of the lowering of this 

 salt in the blood indicates an acidosis. This may be carried out by van Slyke's 

 method described below. 



It has been found that the alveolar CO 2 falls with a fall in the plasma 

 bicarbonate. (This however does not hold with cardio-respiratory 

 cases.) Therefore by determining the CO 2 content of the expired air 

 upon forced expiration we can judge as to reduction of blood carbonate 

 and of course acidosis. 



Sellards' method for determination of serum acidosis is quite simple and reliable. 

 To carry out the test we add i c.c. of serum, drop by drop, to 25 c.c. of absolute 

 alcohol (it is very important to secure a neutral alcohol and I have found that of 

 Merck satisfactory). This precipitates the protein which is the factor interfering 

 with a sharp end reaction. After filtering we add 3 or 4 drops of neutralized phe- 

 nolphthalein solution to the fitrate and evaporate the alcohol in a porcelain dish on 

 a water-bath. Every piece of apparatus must be perfectly dry and the steam vapor 

 of the bath quite low to avoid the taking up by the alcohol of water. In normal 

 cases the dark pinkish tinge of the sediment, after evaporation, will remain at least 

 one hour, while with cases showing increased acidosis the reddish tinging of the 

 sediment disappears in a few minutes. An electric bath is desirable. 



A very simple way of determining bicarbonate diminution is the 

 test for tolerance of alkalis. The giving of 5 grams of bicarbonate of 

 soda to a normal person on a mixed diet will bring about an alkaline 

 urine. Boiling the urine will bring out the alkalinity to litmus more 

 sharply. 



These amounts are increased until the urine becomes alkaline. In some cases of 

 acidosis massive doses of bicarbonate, as 150 grams in one or two days fail to produce 

 an alkaline urine. 



Plasma Bicarbonate. Van Slyke has devised an apparatus for the determination 

 of the carbon dioxide capacity of oxalate plasma. 



He uses i c.c. of the plasma which is shaken with air containing 6% of CO 2 and 

 is introduced into the following apparatus. A 50 c.c. pipette-shaped apparatus is 

 provided at top and bottom with three-way stopcocks and connected with a bulb of 

 mercury. The pipette is first filled with mercury and the plasma having been intro- 

 duced followed by i c.c. of water and 0.5 c.c. of N/i acid the mercury is withdrawn 

 from the pipette by lowering the bulb reservoir, thus creating a Torricellian vacuum. 

 The CO 2 escapes from the solution as the result of a few minutes shaking and the 

 watery solution is drawn off from the lower cock. The mercury is again made to 

 fill the pipette by the other entrance of the three-way cock at the bottom and rises 



