. Physical chemistry of vital phenomena, for students and investigators in the biological and medical sciences. Biochemistry; Chemistry, Physical and theoretical. 64 PHYSICAL CHEMISTRY shaking the solution the colloid may be precipitated in the form of torn membranes, which assume a stringy appearance. In this way enzymes may be inactivated, being either colloidal or pre- cipitated with colloid impurities. The presence of colloids makes an emulsion of oil and water permanent by forming haptogen membranes around the oil drops. It is the haptogen membranes on fat globules in milk that keeps it p
. Physical chemistry of vital phenomena, for students and investigators in the biological and medical sciences. Biochemistry; Chemistry, Physical and theoretical. 64 PHYSICAL CHEMISTRY shaking the solution the colloid may be precipitated in the form of torn membranes, which assume a stringy appearance. In this way enzymes may be inactivated, being either colloidal or pre- cipitated with colloid impurities. The presence of colloids makes an emulsion of oil and water permanent by forming haptogen membranes around the oil drops. It is the haptogen membranes on fat globules in milk that keeps it permanently emulsified, but these membranes seem to be different from caseinogen. Measurement of surface tension is a convenient method of quantitative chemical analysis provided that only one substance grea'tly affecting the surface tension be variable in concentration. It is only necessary to plot the graph of surface tension and con- centration in order to make a table for converting surface tension readings into concentrations. In mixtures, however, the problem may be more difficult. G. D. Allen (1916) measured the surface tension of urine containing different concentrations of bile salts. Bile salts greatly increase the surface tension, but NaCl, which in pure solution slightly raises the surface tension, increases the effect of bile salts in lowering the surface tension. H ions increase the effect and OH ions decrease the effect of bile salts.' late is slightly less effective than sodium glycocholate and, hence, a variation in the proportions of the two salts would slightly affect the result. The following table shows the limits of error when the urine is diluted to a specified specific gravity in order ap- proximately to regulate the concentration of NaCl and other interfering substances. Showing the Amounts of Sodium Glycocholate Required to Give Any Observed Surface Tension in a Sample of Urine Diluted to a Standard Sp. Gr. of S. T. of sample dil
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