Carbon dioxide buffering action

Probably an example and problems derived from the carbon dioxide-blood buffer system in humans should be in every physical chemistry course. What a rich, complex example this is from Henry s law for the solubility of carbon dioxide in water (blood) to buffer capacity, that is, the rate of change of the law of mass action with proton concentration. The example can be expanded to include nonideal solutions and activities. How many physical chemistry courses use this wonderful and terribly relevant to life example First-year medical students learn this material. 

Fillers. The buffering action of an alkaline filler is necessary to ensure permanence in filled paper. Retained alkalinity in the paper as it ages would resist any drop in pH that might result from absorption of either carbon dioxide or sulfur dioxide from the air. Acidic fillers, such as certain types of clay, accelerate the aging process. Calcium carbonate is an ideal filling material for permanent paper as well as for some grades not requiring permanency. In fact, the work of Barrow made the use of calcium carbonate a requirement in the manufacture of permanent book papers (1). 

It is often preferable for physiological purposes to use buffer systems other than the boric acid-borate mixtures. L. Michaelis has found that mixtures of veronal (diethylbarbituric acid) with its sodium salt show a satisfactory buffer action in the neighborhood of pH = 8.0. Pure commercial samples of the sodium salt of veronal are readily available, and may be used frequently without previous recrystallization. Buffer mixtures can be prepared by adding hydrochloric acid to the salt. This compound is water-free, and should suffer no loss in weight when dried at 100°. A 0.1 N solution in water requires exactly an equivalent quantity of 0.1 N hydrochloric acid when neutralized against methyl red. A stock solution should contain 10.30 g. of the sodium salt per 500 c.c. Only carbon dioxide free water should be used. 

Some of the sulphonamides can be used as diuretics. The mechanism of their action relates to carbonic add excretion. Carbon dioxide generated from catabolic processes is carried to the lung and then removed by exhalation. However, part of the carbon dioxide is still dissolved in the blood. Hie dissolved carbon dioxide produces carbonic acid and its conjugated base (i.e. bicarbonate). This mixture of the weak acid and its conjugate base is one of the important buffer systems in the blood. The dissolved carbon dioxide is excreted in the urine. The processes of the conversion of carbon dioxide to carbonic acid and then... 

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