Phenol and tricresol effects in toxin and antitoxin solutions / by C.G. Pope.

  • Pope, C. G.
Date:
[1927?]
Catalogue details

Licence: In copyright

Credit: Phenol and tricresol effects in toxin and antitoxin solutions / by C.G. Pope. Source: Wellcome Collection.

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    pure phenol which separates when they are frozen at some definite temperature depends on the concentration of protein piesent in the mixture. Experiment III— The mixtures containing protein in a concentration greater than 0*37 per cent., which showed no precipitated protein after freezing at — 8° C., were placed in a freezing bath of different composition, the temperature of which was —13 C. At this temperature all mixtures with a protein content of 0*4 per cent, to 1*5 per cent, showed a red colour and after thawing they contained precipitated protein. Here again the limiting concentration (1*5 per cent, protein) showed only a faint pink colour when frozen, and only a trace of precipitated protein on thawing. By lowering the temperature it will be seen that an increased amount of pure phenol is caused to separate and as a result a corre¬ spondingly increased amount of protein is precipitated. The conditions are however rather more complicated than would appear at first sight. Cooper (1912) studied the distribution of phenol between water TT „ _ . Gf phenol in 1 G protein and several proteins. He found the ratio - . Q wftter = 3 provided that the protein was not precipitated by the phenol. From this it follows that the amount of phenol in solution in the water (as distinct from that in solution in the protein) must decrease as increasing amounts of protein are added to the 0*5 per cent, phenol solution. For example we may take 100 c.c. of a solution containing 0*5 per cent, phenol and 1*0 grm. protein. Assuming the ratio given by Cooper to hold for serum protein,* the water will contain 0*485 grm. and the protein 0*015 grm. phenol. The concentration of phenol in the water is 3 per cent, less than would have been the case had no protein been present, i.e., 0*485 per cent, instead of 0*5 per cent. If now 80 per cent, of the water is removed in the form of ice crystals, 20 c.c. of water will contain 0*434 grm. and the protein 0*066 grm. phenol. Here the water contains 13 per cent, less phenol than would have been the case had no protein been present, i.e., 2*17 per cent, instead of 2*5 per cent. The result of increasing the amount of protein in the mixtures is that the initial concentration of phenol present in the water is decreased and a lower freezing temperature is necessary to cause a concentration of phenol in excess of its solubility under the conditions of the experiment. As previously pointed out there is a limiting temperature where the unfrozen portion of the mixture consists of a saturated solution of salt, in which phenol is practically insoluble. Variation in the salt content. The results of varying the salt content can easily be shown by making the variation an extreme one. If a mixture containing about 0*1 per cent, protein in 0*5 per cent, phenol solution is saturated with * The ratio was the same for such widely different proteins as gelatin and egg albumin.