In order that the various functions of the body may be properly performed, it is essential that the blood maintain its slightly alkaline reaction within extremely narrow limits. When this degree of alkalinity is diminished, a condition of acidosis, with its accompanying phenomena, is observed. A truly acid reaction of the blood (that is, a hydrogen-ion concentration greater than pH-7.0†) is incompatible with life.
Various protective mechanisms serve to maintain the acid-base equilibrium of the organism and thereby protect the blood from significant changes in hydrogen-ion concentration. Such processes are increased production of ammonia, the excretion of carbon dioxid by the lungs, the excretion of nonvolatile acids by the kidneys, and finally, the buffer action of the blood itself.1
By the term "buffer action" of a mixture is meant its ability to take up considerable amounts of acid or alkali when these are added to it,
LEVY RL, ROWNTREE LG. A STUDY OF THE BUFFER VALUE OF THE BLOOD. Arch Intern Med (Chic). 1916;XVII(4):525-539. doi:10.1001/archinte.1916.00080100069007