The nature of enzyme action / by W. M. Bayliss.

  • Bayliss, William Maddock, Sir, 1860-1924.
Date:
1914
Catalogue details

Licence: In copyright

Credit: The nature of enzyme action / by W. M. Bayliss. Source: Wellcome Collection.

    41/196 (page 29)
    remaining the same as before; as is familiar to all, the amount of picric acid both in the ether and in the water will be doubled. This is an instance of a physical partition in proportion to relative solubility. Take now a case of a purely chemical reaction such as silver nitrate and hydrochloric acid ; if to a solution of silver nitrate sufficient hydrochloric acid to combine with the silver be added, the whole of the latter will be precipitated, so that the addition of more hydrochloric acid will bring down no further quantity. Take finally a case of an adsorption re- action between colloids, cellulose in the form of filter-paper, which acts precisely like a colloid, and a dilute solution of congo-red. After a certain time it will be found that part of the dye has deposited itself on the paper, but not the whole; that is, the reaction partakes of the nature of both the physical and chemical reactions; physical, in that there is dye both in the paper and in the solution, chemical, in that, like the silver chloride, there is a kind of precipitation. If we double the concentration of the dye we shall find that, unlike the chemical reaction, more congo-red is deposited on the paper ; and unlike the physical pro- cess, it will be found,on making quantitative experiments, that the amount of dye taken up is not doubled, but something less, in fact multiplied by some root of 2 ; in most adsorption processes this root is found to be less than the square root. Expressed in algebraic form, when the concentra- tion of the solution i$ doubled, the amount adsorbed is not multiplied by 2, but by 2 to the power - where n is greater than i, and usually less n than 2, viz., from i’4 to 17. It is obvious, however, that we are justified in applying the name of adsorption to cases of any values of n, less than infinity,^ in which latter case the reaction is purely chemical; - here n becomes o, and all numbers to the power o become unity; in other words, the amount of silver chloride in the example above is always the same whatever the concentration of the hydrochloric acid. When « = I it is plain that the physical process of partition according to solubility is expressed. We see then that the important point about the process of adsorp- tion is that relatively more of the compound is formed in the more dilute solutions. Many important facts in the chemistry of colloids, especially in the relation of toxin to antitoxin, find their explanation in this circumstance. It is of interest to consider for a moment what the expression above 1 Freundlich [1906], who has done much important work on this subject, is frequently understood as limiting the title of “ adsorption ’> to reactions with particular values of this e:tponcnt. It docs not appear from his work that he intended to do this.