Investigations dealing with the phenomena of “clot” formations. Part II.—The formation of a gel from cholate solutions having many properties analogous to those of cell membranes

Abstract

In the first communication under the above title, attention was called to the fact that solutions of sodium cholate, on warming in the presence of calcium salts, set to a gel, which is not reversible on cooling. It has since been found that calcium salts can be replaced by other salts, such as sodium chloride, magnesium chloride, ammonium sulphate and potassium fluoride, and the clot formation is not therefore due to double decomposition between calcium salts and sodium cholate. The concentrations of sodium, potassium, and magnesium salts necessary to produce the “clot” are, however, much higher than that of calcium chloride, which even in the concentration of N/40 can cause 1-per-cent, sodium cholate to set to a solid gel in about a quarter of an hour at 50°. Sodium and magnesium chlorides produce clot formation at 50°, when their concentration is of about the order of half saturation. It is proposed to investigate the relative clotting power of salt in greater detail later; the present communication deals mainly with the question of the influence of one particular factor on gel formation, viz., on the surface tension of the solution. A preliminary account of the clot production by various calcium salts has been given in the first paper ( loc. cit .). It was then shown that in the case of calcium salts which increase the surface tension of water, increase in the concentration of the salt caused a diminution of the clotting time. In the case of the calcium salts which lowered the surface tension, however, the accelerating effect of the increase in the concentration of the salt was counter balanced by the diminished surface tension of the solution. In two cases (those of calcium dichloracetate and of the sulphocyanide) an optimal point was found. Increase in the concentration of the calcium salt above and below this point caused a lengthening of the time required for gel formation. In the case of calcium trichloracetate, the length of clotting time progressively increased with increasing concentration within the limits investigated.