New quantitative observations on the penetration of acids and alkali bicarbonates into living and dead cells

Abstract

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 concentrations of the sap as it came from the cell and containing considerable free CO₂; the other when the free CO₂ was removed by thorough aeration by means of a stream of CO₂-free air. This method showed that normal cells have a P_H of 6.2 to 6.4 when C0₂ is present and 6.6 to 6.8 when CO₂ has been removed. The acids used could be divided into two broad classes with respect to their action on the cells: to the first class belong HCl, HNO₃, H₂SO₄, arsenic, phosphoric, tartaric, citric, oxalic, monodi- 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 CO₂ in the cell-sap, presumably by decomposing the bicarbonates present. When the P_H of the cell-sap had reached 5.2 it remained stationary until no more CO₂ could be detected by the method, the time varying according to the acid used. Acids of the second class penetratedrapidly and produced little or no free CO₂ in the cell-sap. Acids of the first class appear to penetrate less rapidly than they actually do, because instead of existing free in the cell-sap they form neutral salts with the basic ions of the cell bicarbonates.