March 14, 1913] 



SCIENCE 



391 



this neutralization must rest upon physi- 

 ological processes which serve to reestab- 

 lish the original conditions, for if such 

 great amounts of alkali were discharged 

 from the body with the acid excretory sub- 

 stances, the organism would lose its protec- 

 tion and acidity would speedily ensue 

 throughout the system. Thus an impera- 

 tive necessity arises for the retention of a 

 part of the alkali which serves as a carrier 

 in the process of removing acid from the 

 body. Of course the necessary magnitude 

 of such alkali retention by the kidney 

 varies with the net amount of alkali in- 

 gested and with the acid formation of the 

 body. 



The conditions in man are closely par- 

 alleled by those in other higher animals, 

 and there is reason to believe that con- 

 stancy of alkalinity is quite the earliest 

 and most universal physico-chemical regu- 

 lation of active protoplasm. In fact, as 

 the investigations of Palitzsch^ show, the 

 ocean itself is likewise quite constant in its 

 alkalinity. It is worthy of note that this 

 is due to the simultaneous presence of car- 

 bonic acid and bicarbonates in the sea 

 water, a fact which lends support to Ma- 

 callum's ideas about the derivation of the 

 body fluids. Thus active protoplasm every- 

 where, as well as that which surrounds it 

 — the environment and the milieu interieur 

 — appear to be and to have been always of 

 stable reaction. 



According to the modern theory of solu- 

 tion water itself, like the dissolved electro- 

 lytes, is dissociated into ions, though only 

 to a very slight degree. The reaction is 

 expressed thus: 



Hj,0 = H + OH. 



If the water be pure the concentrations 

 of hydrogen and hydroxyl ions are neces- 



« Comptes-rendus des travaux du Ldboratoire de 

 Carlsberg, X., 85, 1911. 



sarily equal, for water is electrically neu- 

 tral. A variety of independent methods 

 of estimation have shown that at 25° this 

 concentration amounts almost precisely to 

 N/10,000,000 in the ordinary units. This 

 corresponds to 0.0000001 gram of ionized 

 hydrogen and 0.0000017 gram of ionized 

 hydroxyl in 1,000 grams of water. Fur- 

 ther, the theory of solution explains acidity 

 in water by the occurrence of hydrogen 

 ions, formed from dissolved electrolytes, in 

 excess of hydroxyl ions ; and alkalinity by 

 a similar excess of hydroxyl over hydrogen 

 ions. Neutrality is, accordingly, the con- 

 dition when, as in pure water, the two con- 

 centrations are equal. In short, expressing 

 the concentration of ionized hydrogen by 

 (H) and of ionized hydroxyl by (OH), if 

 N 

 ^^' ^10,000,000"= (^^^ 



the solution is neutral. If 



(H)>: 



N 



(OH) 



<(0H) 



10,000,000 

 the solution is acid. If 



' 10,000,000 

 the solution is alkaline. 



It remains to point out that implicit in 

 these definitions is the well-founded hy- 

 pothesis that in water the concentrations 

 of hydrogen and hydroxyl ions vary in- 

 versely, so that, with constant temperature, 

 under all circumstances their product is 

 constant : 



(tl) X (OH) =K. 



Thus the nature of acidity and alkalinity 

 may readily be represented by a straight 

 line with the neutral point at its center, 

 acidity increasing in one direction, and 

 alkalinity in the other. 



Whenever a weak acid is present in 

 aqueous solution in company with such 

 bases as sodium, potassium, calcium, mag- 

 nesium, etc., which are invariable constitu- 



