Now, the ionizing power of solvents like water, ammonia, etc., has been ascribed, by various chemists, not only to their dielectric properties, but also to the ‹unsaturated condition of their molecules, and particularly to their powers of association into large molecules›. The relations developed suggest that ‹all three properties are most intimately related›, the dielectric properties and the powers of association being consequences, possibly, of the fundamental condition of unsaturation, and of the great tendency toward self-saturation,[113] of the simple molecules of the best ionizing solvents. From Walden's work it appears that the dielectric constant finally determines the quantitative ionizing effect of a solvent. FOOTNOTES: [49] From the molecular weights of elements and compounds, the atomic weights of elements may be determined, with the aid of analysis. (‹Cf.› Smith, ‹Inorganic Chemistry› (1909), p. 196, or ‹General Chemistry for Colleges› (1908), p. 130 («Stud.»), or Remsen, ‹Inorganic Chemistry, Advanced Course› (1904), pp. 71–80 («Stud.»).) [50] The weight of a small volume of a gas or vapor, at any definite temperature and pressure, is determined. With the aid of Boyle's and Gay-Lussac's laws, this observed volume is then reduced to standard conditions. Finally, the weight of 22.4 liters, under standard conditions, is obtained by calculation. [51] For the deduction of formulæ see Smith, ‹Inorganic Chemistry›, 196, 203; ‹College Chemistry›, 40; or Remsen, ‹ibid.›, p. 79 («Stud.»). [52] Kopp, ‹Liebig's Ann.›, «105», 390 (1858); Kékulé, ‹ibid.›, «106», 143 (1858) («Stud.»). [53] ‹Liebig's Ann.›, «123», 199 (1862) («Stud.»). [54] Wanklyn and Robison, ‹Compt. rend.›, «52», 549 (1863) («Stud.»). [55] For instance in a test tube held in a horizontal position. [56] By applying the corrections demanded by the kinetic theory (van der Waals's equation) to gases even under ordinary pressures, Guye and D. Berthollet have obtained, with the aid of Avogadro's hypothesis, values for the molecular weights of gases and for the atomic weights of their components, which compare in accuracy with the best analytical work on solutions and solids. [57] The usual experimental methods consist in determining the elevation of the boiling-point, or the lowering of the freezing-point, or the lowering of the vapor tension of a solvent by a solute, methods which were discovered by Raoult and used empirically until van 't Hoff developed their relations to the Avogadro principle. The calculation of a molecular weight is much simplified by the use of the different specific constants expressing the lowering or elevation produced by one gram-molecule or mole, dissolved either in one liter or in 100 grams of each specific solvent. [58] See Arrhenius, ‹Z. phys. Chem.›, «1», 631 (1887).