Ts c i i e p e l e v e t z k i (Z. physikal. Chem., 1928, 136, 18— 33, 33— 44).— X IV . The adsorption by various kinds of charcoal of the normal fatty acids from formic to stearic from solutions in water, methyl and ethyl alcohols, acetone, ethyl ether, light petroleum, chloroform, carbon tetrachloride, carbon disulphide, benzene, and toluene has been determined. The curves showing the relationship between the number of carbon atoms in the acid and the percentage adsorption exhibit in the case of solvents containing oxygen in the molecule a sharp minimum in the adsorption at about three carbon atoms, and there
after a steady rise; for all solvents of this group the Traube adsorption law is valid from butyric acid onwards. The curves for the other solvents exhibit at most an ill-defined minimum, and the adsorption shows little agreement with the Traube rule. Water is anomalous, whilst light petroleum, probably since it is a mixture, conforms more to the first group than to the second. There is a qualitative relationship between the power of adsorption and the dielectric constant of solvents of the first group, but this does not hold for solvents of the second group. For the lower members of a homologous series wood charcoal has a greater adsorptive capacity than blood charcoal, but for the higher members the reverse is the case.
The differences in behaviour of wood, sugar, and blood charcoals as regards adsorption arc discussed with reference to the structure of the adsorbing surface.
X V . The adsorption by sugar and blood charcoal of the anions from N/60 solutions of magnesium, calcium, strontium, and barium chlorides, bromides, and iodides has been measured. The quantity adsorbed decreases in all cases in the order I', Br', Cl', the influence of the cation being relatively slight;
beryllium salts exhibit comparatively high adsorption of the anions. The adsorption is not a primary effect, but is the result of an initial formation of insoluble carbonates. Molecular adsorption of certain salts is complicated by the secondary deposition on the adsorbent of insoluble basic salts and hydroxides.
H. F. Gi l l b e.
1088 B R IT IS H CH EM ICAL A B ST R A C T S. A .
So-called hygroscopic water of clays. T.
Ok a z a w a (Sci. Papers Inst. Phys. Chem. Res. Tokyo, 192S, 9, 15— 49).— Isotherms showing the relation between vapour pressure and quantity of water absorbed by clays exhibit discontinuities. The results show that water combines with clay to form hydrates, the composition of which is indicated by the inter
section points on the isotherms. The hydrates form solid solutions, the composition of which depends on temperature and humidity. Adsorption fails to account for the data. R. A. Mo r t o n.
Acidity of acidic earth and alkaline earth.
H . Is o b e and Y . Ye n d o (Bull. Inst. Phys. Chem.
Res. Tokyo, 1928, 7, 805— S20).— The acidity of acid earth is due to the adsorption of acids or acid salts produced by weathering. C. W. Gi b b y.
Crystalline graphite and its capillary pro
perties. R. Co r d e b a s (Chim. et Ind.; 192S, 20, 223— 230).— The capillary nature of the surface of crystalline graphite is discussed in relation to the uses of the latter in industry. The system graphite- water is an illustration of tho author’s explanation of the influence of surface energy on the physical properties of matter. J. Gr a n t.
Variation of the capillary action of solutions with time. H. M. Tr i m b l e (J. Physical Chem., 1928, 32, 1211— 1224; cf. Bigelow and Washburn, this vol., 472).— The variation of capillarity with time has been determined for mixtures of organic solvents at 25° by the capillary-rise method. Mix
tures of ethyl ether with benzene, toluene, and acetone show an increase in capillary rise with time; with the mixtures ether-carbon disulphide, ether-nitro- benzene, and ether-amyl alcohol, the rise is more pronounced. Mixtures of carbon disulphide with benzene, chloroform, and carbon tetrachloride show a fall in the capillary rise with time, whilst pentane and acetone with carbon tetrachloride, and ether with chloroform, show a rise to a maximum followed b y a fall. The systems benzene-toluene, and carbon tetrachloride-chloroform show no change, and the case in which a fall to a minimum is followed by an increase in capillarity has not been observed. The rate and magnitude of any change are greater' the shorter and the smaller is the capillary’- tube used.
Under constant conditions, the nature of the change can be predicted from a knowledge of the surface tension, volatility, and density of the components of the mixture. The conclusion of Washburn and Bigelow (loc. cit.) that preferential evaporation and diffusion account for the results is supported. In closed systems with no rubber connexions, changes in capillary rise with time are prevented, and the authors agree with Washburn and Bigelow (loc. cit.) that to obtain trustworthy data on the surface tensions of mixtures containing a volatile constituent, evaporation must be prevented. L. S. Th e o b a l d.
Electrolytic behaviour of thin films. I.
Hydrogen. II. Areas of catalytically active surfaces. P. P. Bo w d e n and E. K . Ri d e a l (Proc.
Roy. Soc., 1928, A, 120, 59— 79, 80—89).— I. A quantitative investigation has been made of the changes of electrode potential at the surfaces of
metallic cathodes during the electrolytic deposition and removal of minute quantities of hydrogen. The potential of the test electrode was measured against a saturated calomel electrode, using an Einthoven string galvanometer. The cathodes employed were mercury, silver, amalgamated silver, platinum, and platinised surfaces, the electrolyte in most cases being iV/5-sulphuric acid, carefully freed from oxygen by prolonged boiling under reduced pressure and cooling in a hydrogen atmosphere. The marked effect which even a small amount of oxygen has on the apparent rate of growth and decay of hydrogen overvoltage is emphasised. It is found that the electrode potential is a linear function of the surface concentration of the hydrogen, and not, as might be expected if the deposited hydrogen behaved as an amalgam electrode of finite bulk concentration, a logarithmic function.
Moreover, the overvoltage depends only on the surface concentration of the added hydrogen, and is inde
pendent of the nature of the underlying metal.
Apparent differences are due to differences in the real areas of the cathodes, and this gives a method of measuring the accessible areas of metallic surfaces.
The amount of hydrogen deposited (measured by two methods) is very small, the deposition of sufficient hydrogen to form only 1/3000 of an atomic layer raising the potential of the cathode 100 millivolts.
It is shown that the rate of decay, —dT/dt, of the active material is not proportional to F2 as usually assumed, but is an exponential function of the potential, viz., —dr/dt=k1e~k'*B, where E is the elec
trode potential and T the true surface concentration of active hydrogen. The behaviour of the electrode potential and the magnitude of the quantities involved are compatible with the assumption that the potential of the electrode is due to the presence of electric doublets on its surface, the electric moment of these doublets being equal to that given by a proton and a negative hydrogen ion separated from each other by a distance equal to the diameter of a hydrogen atom.
II. The accessible areas of silver, platinum, carbon, and nickel cathode surfaces have been determined by measurement of the amount of deposited hydrogen required to raise the potential by a definite increment, and a comparison has been made of the catalytic activities of these surfaces by observation of the rate of hydrogen evolution. The effects of amalgamation and of treatment of the surfaces by alternate oxidation and reduction, annealing, etching with acid, electro
plating, sand-papering, and rolling have been studied.
The accessible area of bright platinum is about twice, whilst that of platinised platinum is about 2000 times its apparent area. If, however, the platinum is deposited on a mercury surface, the area is sensibly the same as that of mercury. The accessible area of a sand-papered metal is about ten times its apparent area, and in the case of nickel, activation by alternate oxidation and reduction causes an increase of nearly fivefold. Cold rolling reduces the accessible area.
The specific catalytic activities of the various metals for the electro-deposition of hydrogen are found to differ very widely, but for any one metal the specific activity of the surfaces shows only small variations with chemical or thermal treatment. The effect of
G E N E R A L , P H Y S IC A L , A N D IN O R G A N IC C H E M IS T R Y . 1089 alternate oxidation and reduction is chiefly to increase
the accessible area by altering the grain size. Violent mechanical treatment, however, although it increases the surface to a much smaller extent, increases the proportion of surface atoms which are out of the crystal lattice and are catalytically the most active.
The increase of activity gradually diminishes with ageing of the cathode. L. L. Bi r o u h s h a w.
Benzyl ether as a cryoscopic solvent. G. M.
Be n n e t t and G . H . Wi l l i s (J.C.S., 1928, 2305—
2307).— Benzyl ether purified by fractional freezing has m. p. 3-60°, b. p. 184°/2 mm., mean cryoscopic constant 62-7, and latent heat of fusion 24-4. For benzoic and acetic acids the apparent mol. wt. is less than when benzene is used as solvent, but the values are the same for benzyl alcohol. This is said to be due to the tendency for ethers to form complexes with hydroxylic substances. J. Gr a n t.
Cryoscopic determination of the molecular equilibria of resorcinol and pyrocatechol in aqueous solution. F. Bo u r i o n and C. Tu t t l e (J.
Chim. phys., 192S, 25, 485— 496 ; cf. this vol., 233).—
A t 0°, equilibria exist between simple and triple molecules in solutions of resorcinol (0-7-3A/) and pyrocatechol (0-3-1-251/), but for concentrations less than 0-7M and 0-31/, respectively, jqo equilibria were detectable between simple and double molecules. At 100°, the ranges of concentration for single-double molecules are 6-375-1-254/ and 0-25-1 -0625M , and for single-triple molecules T375-2.il/ and T125-TS75J1/, for resorcinol and pyrocatechol, respectively. The association of resorcinol decreases and that of pyro
catechol increases with rise in temperature, and the heats of association of 3 molecules to a triple molecule in aqueous solution at constant volume are + 600 and
—2400 g.-cal.,respectively. J. Gr a n t.
Dielectric constants of solutions of electrolytes.
H . He l l m a n n and H . Za h n (Ann. Physik, 1928, [iv], 8 6 ,6S7— 716).— A reply to Walden, Ulich, and Werner (this vol., 14). The experimental method used by the latter is regarded as subject to errors which are unimportant in the study of non-conducting liquids, but increase in significance as the conductivity increases. Theoretical and experimental evidence is adduced which tends to show that the recorded large decrease in dielectric constant in solutions of electro
lytes is not real. R. A. Mo r t o n.
Absorption spectra of solutions of cobalt chloride, cobalt bromide, and cobalt iodide in concentrated hydrochloric, hydrobromic, and hydriodic acids. W . R. Br o d e and R. A. Mo r t o n
(Proc. Roy. Soc., 1928, A, 120, 21— 33).— By means of the apparatus previously described (cf. this vol., 45S), a more detailed study has been made of the absorption spectrum of cobalt chloride in concen
trated hydrochloric acid in the blue and green portions of the visible spectrum (400— 600 tm). An extension of the analysis previously applied to the selective absorption between 600 and 720 ¡41 to the whole of the absorption spectrum under investigation indicates that the fine structure in the blpe and green regions is a continuation of the vibrational system previously observed (loc. cil.). The absorption spectrum of
cobalt bromide in hydrobromic acid has also beon determined throughout the visible portion of the spectrum, and that of cobalt iodide in hydriodic acid between 500 and 900 n<x, by a combination of visual and photographic methods. The absorption of the systems investigated is clearly influenced by the nature of the anion; the replacement of a lighter by a heavier halogen atom causes a shift of the absorption bands in the direction of lower frequencies, and increases the intensity of the low-frequency com ponents as compared with the high-frequency com ponents of the principal band. In the case of cobalt chloride, the resolution of the principal band into its components can be made only on the assumption of six constituents, and this probably holds also for the bromide and iodide. By this method of analysis, the principal band is composed in all cases of com
ponent bands, the frequencies of which are from 35 to 40 times the constant frequency difference between these components, this frequency difference being 12-28,11-70, and 10-79 / , respectively, for the chloride, bromide, and iodide systems. L. L. Bi r c u m s h a w.
Refraction and dissociation of electrolytes.
II. In methyl and ethyl alcohol. E. Sc h r e i n e r
(Z. physikal. Chem., 1928, 135, 461—47 2 ; cf. this vol., 708).— The molecular refraction of hydrochloric acid and of lithium chloride in methyl and in ethyl alcohol has been measured. The refraction falls with increase of concentration, probably due to a deformation of the medium duo to solvation of the cations. The refraction is greatest in water, less in methyl alcohol, and least in ethyl alcohol. The dissociation constants of the first and second kinds of hydrochloric acid in water are discussed.
W . E . Do w n e y.
Chemical change of acids and salts in solution from the point of view of refractometric data.
A. Ha n t z s c h and F. Du r i g e n (Z. physikal. Chem., 1928, 136, 1— 17).— Measurements have been made of the densities and refractive indices of aqueous and alcoholic solutions of various acids and their alkali and alkaline-earth salts (cf. this vol., 834).
H . F. Gi l l r e.
Affinity between asymmetric ions. I and II.
S . W. Be r g m a n (Arkiv Kemi, Min., Geol., 1928, 9, Nos. 34 and 42, 1—21, 1— 11).— I. Conductivity measurements at 18-0±0-2° have been made with solutions of cinchonine d- and Z-mandelates, cinchonine d- and Z-tartrates, and quinine d- and Z-camphor- sulphonates. The values for A for each pair of diastereoisomeric salts were found to be approxim
ately equal. Measurements of [a]««, for cinchonine d-, Z-, and r-mandelates show that the values [ot]d—[a]r are about the same as [a];—[a]r and [a])^ the Same as for ammonium Z-mandelate. There is thus no difference in affinity between optically active acids and bases (cf. Marckwald and Chwolles, A., 1898, ii, 371). The difference in solubility of diastereo
isomeric salts is explicable in terms of the energy content of the crystal lattice., and the Bjerrum dis
sociation theory affords a satisfactory explanation of the results.
II. A series of density determinations has been made with 8 pairs of crystalline and anhydrous
1090 B R IT IS H CH E M ICAL A B ST R A C T S .— A .
diastereoisomeric salts. The results show that in general the heavier salt has the smaller solubility.
H. Bu r t o n.
Affinity. I ll and IV. H . v o n Eu l e r (Arkiv Kemi, Min., Geol., 1928, 9 , Nos. 30 and 44, 1— 6, 1— 6).—Theoretical. The author cites examples of fission which may be explained in terms of the affinity between reactant groups and atomic groups of the
substrate. H. Bu r t o n.
Copper hydrosols of low electrical conduct
ivity. G. T. R. Ev a n s (Trans. Faraday Soc., 1928,
2 4 , 409— 412).—Very dark brown copper sols, of specific conductance less than 0-6 mho, majr be prepared by striking an arc between a heavy rotating copper cathode and a light copper anode in a cooled vessel containing water of low conductivity. About 8— 10 amp. at 80 volts are passed for 2 hrs. and the resulting sol is kept for a day so that the larger particles torn from the electrodes may settle.
F. G. Tr y h o r n.
Protected silver hydrosols. VI. Sol form
ation by irradiation. J. Vo i g t (Kolloid-Z., 192S,
4 5 , 319— 322).— In order to reduce very dilute solutions of silver nitrate (0-106—0-0106%) and silver oxide (0-005%) by irradiation with a quartz-mercury lamp, the presence of reduction centres is necessary.
Sols are not obtained, therefore, after the solutions have been passed through an ultra-filter. Pure gum arabic, before and after irradiation, cannot reduce dilute silver nitrate. Irradiation of a mixture of silver solution and gum arabic effects reduction, giving a precipitate with visible light and forming a silver sol with ultra-violet light. The submicrons of the gum arabic appear to act as reduction nuclei.
Ultra-violet light has a peptising influence, for the precipitated silver can be dispersed to a yellow sol by shaking during irradiation. E. S. He d g e s.
Orange-coloured or orange-red colloidal gold solutions. P. P. v o n We i m a r n (Kolloid-Z., 1 9 2 8 , 4 5 , 366— 370).— Directions are given for the pro
duction of orange gold sols. Solutions of auric chloride and sodium citrate are mixed together in boiling distilled water and a small quantity of dilute potassium cyanide solution is subsequently added.
The whole is then kept boiling for a period of many hours. 'Excess of potassium cyanide gives a quite colourless solution. The sols remain stable for some months; they generally become pure red in time.
The change from orange-red to orange on addition of potassium cyanide is considered to be caused by the greater velocity of dissolution of the red colouring ultramicro-crystals of gold. Examples are also given of orange gold sols, the colour of which is due to suspension of a red sol in a yellow dispersion medium (often produced by the action of alkali on reducing substances such as sugar etc.), and it is pointed out that the colour of a sol is not a safe guide to its degree of dispersion. E. S. He d g e s.
Colloidal platinum. IV. Existence of hexa- hydroxyplatinic acid in colloidal platinum solutions. S. W. Pe n n y c u i c k (J.C.S., 1928, 2108—
2117; cf. this vol., 476).— When the clear solution obtained after coagulation of a platinum sol by freezing is conductimetrically titrated, curves are
obtained which are closely similar to those obtained with hexahydroxyplatinic acid, H2Pt(OH)G, the only known'strong platinic acid. The acid, lower hydrates of which are probably also present, is probably produced by oxidation during the atomisation of the platinum, and forms part of the colloidal micelle. Its ionisation at the surface would account for the stability of the colloid, coagulation by bases being due to neutralisation. Initial preservation of the acid by means of a freezing mixture is essential for the pre
paration of a strong stable sol. J. Gr a n t.
Stability of colloidal ferrous phosphate pre
pared by means of gelatin or blood-serum.
M . Me s s i n i (Kolloid-Z., 1 9 2 8 , 4 5 , 3 2 2 — 3 2 5 ) .—
Following the observation that intravenously in
jected ferrous sulphate is transformed in the animal body to colloidal ferrous phosphate, the stability of colloidal ferrous phosphate in presence of gelatin and of blood-serum has been studied. The material was prepared by mixing solutions of sodium phosphate and ferrous sulphate in presence of the colloid, and the time interval between mixing and the appearance of flocculation was noted. The protective action of gelatin is observable at a concentration of 2 -5 g. per litre and reaches a maximum at 1 2 -5 g. per litre, thereafter remaining constant. The smaller the concentration of ferrous phosphate the greater is its stability ; the colloid remains stable for an indefinitely long period at a concentration of 0 -0 0 6 g. per litre and in presence of 1 2 -5 g. per litre of gelatin. Similar results were obtained with ox-blood serum as thé protective colloid. The protective effect is observed at a concentration of 100 c.c. per litre and the colloid seems to be permanent^ stable when the concentra
tion of ferrous phosphate is 0 -0 0 6 g. per litre and that of serum 7 0 0 c.c. per litre. E. S. He d g e s.
Influence of concentration of a sol on its stability. S. G. Ch a u d h u r y (J. Physical Chem.,
1 9 2 8 , 3 2 , 1 2 3 1 — 1 2 3 5 ) .—Mainly polemical against Ghosh and Dhar (A., 1 9 2 7 , 3 0 5 , 6 1 7 ). The possi
bility that a decrease in the charge of a sol with dilution will tend to sensitise it has been overlooked by previous workers. In explanation of the variation of the coagulating concentration for different electro
lytes with dilution it is suggested that the diminution of the charge and of the total surface of sol particles with dilution tends to make the sol unstable if the potential at which the sol coagulates and the relative adsorption of all ions on the surface remain un
changed. The greater distances between the particles of a diluted sol favour stability. L. S. Th e o b a l d.
Particle size in precipitated zinc sulphide.
G. R. Le v i and C. G. Fo n t a n a (Atti R. Accad. Lincei,
1 9 2 8 , [vi], 7 , 5 0 2 — 5 0 8 ).— The particle size of zinc sulphide, obtained by passing excess of hydrogen sulphide into solutions of zinc salts, has been examined by an X-ray method. The solutions used were N-zinc sulphate with, respectively, A7-sodium hydroxide, AT-ammonia solution, iV-acetic acid, and iY-acetic acid with A7-ammonium acetate. The precipitate was kept for 2 4 hrs. before examination ;
1 9 2 8 , [vi], 7 , 5 0 2 — 5 0 8 ).— The particle size of zinc sulphide, obtained by passing excess of hydrogen sulphide into solutions of zinc salts, has been examined by an X-ray method. The solutions used were N-zinc sulphate with, respectively, A7-sodium hydroxide, AT-ammonia solution, iV-acetic acid, and iY-acetic acid with A7-ammonium acetate. The precipitate was kept for 2 4 hrs. before examination ;