384 



Scientific Proceedings (131) 



185 (2145) 



New quantitative observations on the penetration of acids and 

 alkali bicarbonates into living and dead cells. 



By M. M. BROOKS (by invitation). * 



[From the Division of Pharmacology, Hygienic Laboratory, 

 Washington, D. C] 



Cells of the green alga Valonia from which cell-sap can be 

 obtained free from contamination in sufficient quantities for 

 accurate observation were placed in solutions of acids dissolved 

 in sea water. The concentrations of acid were such so as to give 

 a P H of 3.6. At intervals cells were taken out and the H ion 

 concentration of the sap noted. It was found that two sets of 

 observation were necessary ; one set comprised the H ion concen- 

 trations of the sap as it came from the cell and containing con- 

 siderable free C0 2 ; the other when the free C0 2 was removed 

 by thorough aeration by means of a stream of C0 2 -free air. 

 This method showed that normal cells have a P H of 6.2 to 6.4 

 when C0 2 is present and 6.6 to 6.8 when C0 2 has been removed. 

 The acids used could be divided into two broad classes with re- 

 spect to their action on the cells : to the first class belong HQ, 

 HN0 3 , H 2 S0 4 , arsenic, phosphoric, tartaric, citric, oxalic, mono- 

 di- and tri-chloracetic acids. To the second class belong acetic, 

 butyric, benzoic and salicylic acids. All the acids of the first 

 class increased the amount of free C0 2 in the cell-sap, presum- 

 ably by decomposing the bicarbonates present. When the P H 

 of the cell-sap had reached 5.2 it remained stationary until no 

 more C0 2 could be detected by the method, the time varying ac- 

 cording to the acid used. Acids of the second class penetrated 

 rapidly and produced little or no free C0 2 in the cell-sap. Acids 

 of the first class appear to penetrate less rapidly than they ac- 

 tually do, because instead of existing free in the cell-sap they 

 form neutral salts with the basic ions of the cell bicarbonates. 

 The carbonic acid liberated in this process is so weak as to have 

 relatively little effect on the P H . 



i Published by permission of the Surgeon-General, United States Public 

 Health Service. 



