THE ATTRACTION PRESSURE BY J. TRAUBE
In different physiological’ and physico-chemical papers I have discussed the attraction pressure (Haftdruck) of a dissolved substance. This expression means the cohesion constant a,, of van der Waals. The attraction pressure is the intensity factor of the solution energy and has been neglected in the theories by van’t Hoff and Arrhenius. If for example we dissolve in water a substance like sugar or alcohol, we change the energy content of the system t o a certain extent. This change is proportional, firstly to the number of the dissolved particles-that is a capacity factor-and proportional secondly to an intensity factor the attraction pressure,” that is the pressure, which corresponds to the union of the substance and the solvent. There i s scarcely a single Physical or physiological property of the solutions, which i s not intimately connected with the attraction pressure. Though I have already published different memoirs concerning this pressure, my ideas have changed and enlarged in different ways, and therefore I wish to put together in a new paper the attraction pressures firstly of the ions, secondly of the nun-electrolytes in their relations to the physical and physiological properties of the substances. I wish t o mention here the physiological part of these problems only in a brief manner. That is necessary, because the physiological part of my work is very important for the understandiiig of my theory and therefore I refer to my newest publications in the Biochem. Zeitschrift and in Pfliiger’s Archiv. f . d . ges. Physiologie. ‘ I
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Pfliiger’s Arch. ges. Physiol., 105, 541, 559 (1904); 123, 419 (1908); Arch. exper. Pathol. und Therap., 2 , 117 (1905); Biochem. Zeit., IO, 371-403 (1908); 16, 183 (1909); Bickel, Deutsche med. Woch., 1905, No. 28. 2 Verh. phys. Ges., 6, 326 (1904);IO, 880 (1908); Ber. chem. Ges., Berlin, 42, 86, 1594, 2185 (1909).
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1. The Ions I. Surface tension. '-1 have chosen the following form for a well-known principle by Gibbs: T h e more a substance increases or decreases the surface tension of the pure solvent, the larger or smaller is its attraction pressure. Therefore the order of the surface tensions of molecular solutions is identical with the order of the attraction pressures and thus I calculated from my own experiments with alkali saltsZ the following order of attraction pressures for the best known ions:
Anions: C10, < CNS < I ; C10,< CN < NO, < NO, < Br; C1< OH < F < C,H,O, (tartaric acid) < SiO, Br > C1> OH > SO, > CO,. Cations: H > NH, > Li(hydr.) > K > Na.
3 . Diminution in the s~lubili.ty.~-It is known that salts diminish the solubility of gases, non-electrolytes, colloids and suspensions. As stated by Geffken, there derives from the alkali-salts-in general-the following series : Anions : CNS < I ; C10, ; NO, < Br < C1< OH < SO, < CO,. Cations: H < Cs < Rb < NH, < Li(hydr.) < K < Na.
As shown, here the series of the ions is like that for surface tension and compressibility, but sometimes the lithium ion has its place at the other side of the sodium. Why that is the case, we may conclude from: Comp. Verh. phys. Ges., IO, 888 (1908). Ibid., IO, 888 (1908), there reference is made to further attraction pressures. 3Verh. phys. Ges., IO, go3 (1908). LOC.cit., p. 895.
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4. The hydrate formation and the electrical transference. lWe derive from the hydrate formation of the salts in the solid state as well as in the state of aqueous solutions according t o Smirnow, Jones, Garrard and Oppermann, Washburn, Heydweiller and others the following series : Anions (Garrard and Oppermann) : NO3< Br < C1 C N S > B r . That is the same series as in general for the solubilities of the salts in organic solvents. I 4,Ionic velocities. Anions : CIO, < NO, < C1; I ; Br < OH. Cations : H ; Cs > Rb > NH,K > N a > Li.
The attraction pressure is not the sole but the most important coefficient, from which depends the order of the ionic velocity and therefore the electrical conductivity. The cations with the lowest attraction pressure have the highest velocity and just the inverse is the case with the anions. I 5 . Decomposition ~oltage.~--From the experiments of Walden and Centnerszwer: Zeit. Elektrochemie, 15, 310 (1909) Verh. phys. Ges., Io, 909 (1908). Ibid., IO, 911 (1908).
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Wilsmore and Nernst we obtain the following series of the decomposition voltages for the anions : Anions: I < Br < NO, < OH < F SO, > C,H,O > C1> NO,, Br > I. ' This is again the series of attraction pressures. I 8. Thermoelectric forces. ,-The thermoelectric forces, which appear in solutions of salts of the same acid or base when there is a difference of temperature, may be arranged in the following order: Anions : SO, > C1> I. Cations: Li > NH, > N a > K > Rb > H ; M g > Ca> B a > Fe.
With the exception of the ammonia we find once more the series of attraction pressures. 19. Passivity. 4-From Hittorf's researches we get the following series of monobasic anions arranged with reference t o the corrosion and passivity (Passhierung) of the chromium anode : Anions : F > C1> NO, > CN > Br > CNS > I.
That is again the series of attraction pressures. l T r a u b e : Ber. chem. Ges., Berlin, 42, 1601 (1909). Ibid., 42, 1601.(1go9). 8 P o d ~ z u s Drude's : Ann., 27, 859 (1908). Traube, Ber. chem. Ges., Berlin, 42, 1600 (1909).
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20. M a x i m u m of surface tension. '-According toz. the careful measures by Gouy the anions of the alkali salts influence the maximum of surface tension in the electrometer by Lippmann in the following order:' Anions : P,O, > PO, > CO,; SO, > O H > C,H,O, ; C1> NO, > Br > CNS> J, S. That i s exactly the series of the attraction pressures. 2 I . Osmotic processes.-These processes are especially important from the point of van't Hoff's theory. The most simple processes refer t o the swelling or shrinking of gelatine and glue studied by Hofmeister3 and his scholars. The gelatine swells in the chlorides, bromides, nitrates and iodides of the potassium salt solution, but it shrinks in the solutions of the sulphates, tartrates, citrates and acetates. This antagonism of the same sfiecies of ions4 (compare velocity of reaction) exists in the same manner with regard to the cations, K, Na, etc., as opposed to the ions Ca, Mg, etc. There are many physiological processes influenced by this antagonism. The order of the anions with regard to the swelling of the gelatine is the following :5 SCN > J > Br > NO, > C1> C,H,O > C,H,O, > SO,. There are also the highly remarkable osmotic researches b y Brown' on the osmosis penetration of water into the covering of barley, when we put a certain quantity of the seed of barley in equivalent solutions of salts. The covering of barley is only permeable for salts of a very low attraction pressure as HgCl,, CdJ,; the rate at which the water passed into the barley increased from Na : K : NH, and from
Loc. cit., p. 1600. Compare there further anions. These observations of Gouy seem to be the most important and reliable for the statement of a series of attraction pressures. a Compare Hoeber: Zeit. phys. Chem., 70, 5, 143 (1910). Hoeber: Phys. Chem. der Zelle and Gewebe, further Traube, Mengarini and Scala, Biochem. Zeit., 17, 443 (1909); Pick and Schwarz: Ibid., 17,491 (1909); and J. Loeb: Parthenogenese. H. Barth, Eeipzig. Compare Hoeber: LOC.cit. Brown: Proc. Roy. SOC.,81, (1909) and my latest publications in Biochem. Zeit., March, 1910.
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J : C1 : NO,.
Hoeberl has found that the velocity of haemolysis increases from SO, : Cl : Br; NO, : J and Li; Na : Cs; Rb : K. As to the changes in the series of the cations as to physiological processes, compare Hoeber. In the plasmolytic researches of de Vries' the order of the alkali ions is the following one: SO,-C1-NO, and K-NH,-NaLi. The swelling of the muscles increases (compare J. Loeb4) from Li : Na : K. According t o Schwenkenbecher' lithium salts do not penetrate into the skin of the frog, but potassium iodide diffuses and Hedin' found that the diffusion through dead intestine of beef increases in the order: SO, : C1 : NO, : Br and Mg : Li : Na : Rb : K. Even for the living intestine there exist only small changes in the series of attraction pressures. Other important physio2ogical processes.-The capability t o precipitate albumen diminishes according to Hofmeister and Pauli' in the following order: SO, : HPO, ; C,H,O, : C1 : NO, : Br : J : CNS and Li : Na : K : NH,. The alteration of the melting or freezing point of gelatineg also shows the series of attraction pressure and Overtonlo has found with regard t o the irritability of the muscles the following order of anions : HPO,, SO,, C,H,SO,, CH,COO, (CHOHCOO),, C1, Br, NO,, I, CNS and the order of cations: I,i, Na, Cs, Rb, K. The ions with the lower attraction pressure cause an inflow of water in the muscles, but ions with a higher attraction pressure do not do so. ________I
Hoeber: L O ~cit. .
LOC.cit. de Vries: Zeit. phys. Chem., 2 , 427 (1888); 3, 109 (1889). Compare Koranyi and Richter: Handbuch. phys. Chem. and Medizin, Vol.
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Schwenkenbecher: Compare loc. cit., Vol. I, p. 344. Hedin: Pfluger's Arch., 78, 205 (1899). 7 Compare my publications in Biochem. Zeit. 8 Hofmeister and Pauli: Compare Hoeber: Phys. Chem. der Zelle and Gewebe, I1 edit., p. 241. Hoeber: Phys. Chem. der Zelle and Gewebe, 11, p. 2 5 5 . '0 Hoeber, loc. cit., 2 7 3 and Biochem. Ze:t. 14,2 1 0 (1908). 5
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The A ttracti0.n Pressure
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Concerning the irritability’ of nerves, Mathews, Griitzner and Hoeber draw up the following order: I
