Volumes and heat capacities of anionic-nonionic surfactant mixtures

Density, heat capacity and surface tension measurements of sodium decylsulfate (NaDeS)-dodecyldimethylamine oxide (DDAO)-water mixtures were carried out as functions of the surfactants total molality m_t at fixed stoichiometric mixture compositions X_NaDeS. From the surface tension data, the critical micelle concentration of NaDeS-DDAO mixtures as a function of X_NaDeS were obtained. From density and heat capacity data, the apparent molar volume V_,2 and heat capacity C_,2 of NaDeS-DDAO mixtures in water were calculated, respectively. At a given mole fraction, V_,2 and C_,2 monotonically increases and decreases, respectively, with increasing mt. However, anomalies were observed at X_NaDeS=0.1 and 0.3 for both V_,2 and C_,2 vs. mt curves. The nonideal contributions to the thermodynamic properties for the formation of surfactant-surfactant mixed micelles in water by mixing aqueous solutions of pure NaDeS and DDAO micelles were calculated at 0.3 mol-kg^–1 for the micellized surfactants mixture. The excess volume V^exc and heat capacity as functions of X_NaDeS are concave and S-shaped curves, respectively. All the properties are compared to those for sodium dodecylsulfate-DDAO mixture. In addition, to clarify the effect of the change in the hydrophobicity of the surfactants mixtures V^exc for the dodecyltrimethylammonium bromide-decyltrimethylammonium bromide mixture were calculated from literature data.     

Thermodynamic studies of octyltrimethylammonium chloride in water

Densities, heat capacities, enthalpies of dilution at 298 K and osmotic coefficients at 310 K of octyltrimethylammonium chloride were measured as functions of concentration. From the experimental data, the partial molar volumes, heat capacities, relative enthalpies, nonideal free energies and entropies at 298 K were derived as functions of concentration. A comparison between the above data and those of dodecyltrimethylammonium chloride reported in the literature shows that the increase of the alkyl chain length shifts the apparent molar volumevs. concentration curves towards greater values and the heat capacity, relative enthalpy and free energyvs. concentration curves towards smaller values. By assuming the pseudo-phase transition model the properties of micellization (Y_m) were graphically evaluated. TheY_m values of OTAC compared with those of DTAC are consistent with the increase of the hydrophobicity by increasing the alkyl chain length.The authors are grateful to the National Research Council of Italy (CNR, Progetto Finalizzato Chimica Fine II) and to the Ministry of University and of Scientific and Technological Research (MURST) for financial support.     

Thermodynamic properties of N-octyl-, N-decyl- and N-dodecylpyridinium chlorides in water

Densities, heat capacities and enthalpies of dilution at 25°C and osmotic coefficients at 37°C were measured for N-octyl-, N-decyl- and N-dodecyl-pyridinium chlorides in water over a wide concentration region. Conductivity measurements were performed in order to evaluate the cmc and the degree of counterion dissociation. Partial molar volumes, heat capacities, relative enthalpies and nonideal free energies and entropies at 25°C were derived from the experimental data as functions of the surfactant concentration. The changes with concentration of these properties are quite regular with the exception of the heat capacities which display anomalies at about 0.9, 0.25 and 0.12 mol-kg^–1 for the octyl, decyl and dodecyl compounds, respectively. At these concentrations there were also changes in the slopes of the specific conductivity and of the product of the osmotic coefficients and the molality vs. concentration. These peculiarities can be ascribed to micelle structural transitions. The thermodynamic functions of micellization were graphically evaluated on the basis of the pseudo-phase transition model. These data have been compared to those for alkyltrimethylammonium bromides and alkylnicotinamide chlorides. It is shown that the introduction of the hydrophilic CONH₂ group lowers the hydrophilic character of the pyridinium ring.     

EXAFS Study of Ph3GeMn(CO)5 Structure Evolution on Exposure to X-Radiation

Ge K-edge and Mn K-edge EXAFS spectroscopy was used to study changes in the local environment of germanium and manganese atoms during radiolysis of the Ph₃GeMn(CO)₅ complex. On exposure to X-radiation, the metal complex undergoes a number of transformations depending on the radiant exposure (). It was shown that at = (6–8) × 10⁶ J/m², the initial metal complex decomposes into the [Ph₃Ge] and [Mn(CO) _n ] fragments with partial detachment of the CO groups from Mn atoms. When = 1.3 × 10⁷ J/m², Mn atoms lose completely the CO groups to form finely dispersed metal nanoparticles, which interact with the surrounding atoms (carbon or nitrogen). With further increase in , the local environment of the Mn atoms no longer changes. The Ge atoms remain coordinated to the Ph groups as increases up to 2 × 10⁷ J/m², but starting with = 1.6 × 10⁷ J/m², metal–metal bonds are formed; subsequently, the amount of this phase increases and when = 2.6 × 10⁸ J/m², it becomes predominant. Since manganese and germanium atoms lose their ligands at different values, one can conclude that germanium and manganese nanoparticles are the final products in the radiolysis of Ph₃GeMn(CO)₅.     

Radiolysis of [EtC5H4Mn(CO)2NO]+(PF6)– and Evolution of the Nearest Environment of the Manganese Atoms in the Complex

X-ray emission and EXAFS spectroscopies were used to examine changes in the nearest environment of manganese atoms upon radiolysis of [EtC₅H₄Mn(CO)₂NO]⁺(PF₆)^– at different energy exposures (). It was found that the initial complex loses the CO and NO ligands at = 4.5 × 10⁶ J/m². An increase in to 7.5 × 10⁶ J/m² gives rise to Mn–Mn bonds with lengths characteristic of Mn dimers. At = 9.0 × 10⁶ J/m², Mn nanoparticles are formed; they interact with the carbon atoms of EtC₅H₄ and the fluorine atoms of PF₆ anions. Further increase in = 2.6 × 10⁷ J/m² yields manganese-containing nanoparticles structured like metallic Mn; their surface atoms interact with carbon atoms formed in the disintegration of the EtC₅H₄ ligands. The formation of manganese carbides and fluorides at = 2.6 × 10⁸ J/m² reduces the content of the metal constituent in nanoparticles; this content is zero at = 4.4 × 10⁸ J/m². The final radiolysis products are manganese carbides and fluorides (or fluorocarbides).     

Photochemische Carbonylierung und Oxydation von wässerigem Methanol bei 1470 Å

Zusammenfassung Das photochemische Verhalten von wässerigem Methanol, gesättigt mit Argon, CO bzw. O₂ wurde bei 1470 Å als Funktion der VUV-Dosis und der Methanolkonzentration untersucht. Als Reaktionsprodukte wurden Wasserstoff, Formaldehyd, Glykolaldehyd, Glykol, Ameisensäure und in Gegenwart von Sauerstoff auch Peroxyd nachgewiesen. In 10^–2 m-Methanol, gesättigt mit Argon, betrug (H₂)=0,69 und (HCHO)=0,22, in Gegenwart von 7·10^–4 m-CO war (H₂)=0,10 und (HCHO)=0,29, während bei Sättigung mit O₂ (10^–3 mO₂) (H₂)=0,01, (HCHO)=0,33, (HCOOH)=0,20 und (H₂O₂)=0,22 gefunden wurde. Die -Werte der übrigen Produkte, die unter den angegebenen Bedingungen erhalten wurden, waren <0,07. Durch Erhöhung der Methanolkonzentration bis zu reinem Methanol, gesättigt mit Argon, stieg die Ausbeute von H₂, HCHO und (CH₂OH)₂ entsprechend an, während die von HCOOH und CH₂OHCHO sich praktisch nicht änderte. Bei reinem, mit Argon gesättigtem Methanol war (H₂)=0,89 und (HCHO)=0,73. Das Glykol erreichte bei etwa 2m-Methanol eine Höchstausbeute von =0,38. Reaktionsmechanismen werden diskutiert.

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Photochemical carbonylation and oxidation of aqueous methanol at 1470 Å

The photochemical behaviour of aqueous methanol saturated with argon, CO and O₂, resp., has been investigated at 1470 Å as a function of the v.u.v. dose and the methanol concentration. Hydrogen, formaldehyde, glycolaldehyde, glycol, formic acid and, in the presence of oxygen, also peroxide were detected. In 10^–2 M-CH₃OH saturated with argon (H₂)=0,69 and (HCHO)=0,22 were found; in the presence of 7·10^–4 M-CO the yields are (H₂)=0,10 and (HCHO)=0,29, whereas under saturation with oxygen (10^–3 M O₂) (H₂)=0,01, (HCHO)=0,33, (HCOOH)=0,20 and (H₂O₂)=0,22. The quantum yields of all other products obtained under the conditions mentioned above are <0.07. With increasing methanol concentration up to pure argon saturated methanol, the quantum yields of H₂, HCHO and (CH₂OH)₂ increase correspondingly, whereas the yields of HCOOH and CH₂OHCHO remain practically unchanged. When irradiating pure, argon saturated methanol, (H₂)=0,89 and (HCHO)=0,73 were found. A maximum yield of (CH₂OH)₂=0,38 was achieved using 2M-CH₃OH. Reaction mechanisms are discussed.

     

3, 3, 3-Trifluoropropyl(methyl)cyclosiloxanes

The catalytic rearrangement of the cyclopentasiloxanes _mD_5-m, where represents a 3, 3, 3-trifluoropropyl(methyl)siloxane link and D a dimethylsiloxane link, and m=2–5 has been studied by the method described previously [1]. The rate of rearrangement and the rate of formation of a linear polysiloxane rise with an increase in m from 2 to 4. The equilibrium concentration of the linear polysiloxane formed from _mD_5-m and from _mD_4-m (m=0–4) [1] is inversely proportional to the molar fraction of links in the ring and rises with an increase in the total concentration of siloxane links in solution. Results have been obtained on the kinetics of the formation of the cyclosiloxanes _mD_n (where m=0–5, n=0–5, and m+n=3-6) during the rearrangement of the cyclopentasiloxanes _mD_5-m. It has been established that at equilibrium a mixture of cyclosiloxanes _mD_n containing practically constant ratios of tetramers, pentamers, and hexamers (m+n=4, 5, and 6) is obtained, regardless of the composition and structure of the initial cyclosiloxane and of the conditions of rearrangement (polymerization). The cyclopentasiloxanes _mD_5-m are less active in the process of rearrangement than the cyclotetrasiloxanes _mD_4-m. The activity of the cyclosiloxanes in rearrangement in the presence of a base rises in the sequence D₄D_{3 2}D₃<₃D₂<₄D < ₂D₂ < ₃D.For part II, see [1].     

Enthalpies of mixing of some nitriles aqueous solutions with dodecylsurfactants micellar solutions

The enthalpies of mixing of some n-nitriles (from acetonitrile to valeronitrile) aqueous solutions with dodecyltzimethylammonium bromide, sodium dodecylsulfate and dodecyltzimethylammonium oxide micellar solutions were determined. The measurements were performed by systematically changing the surfactant concentration at a given solute concentration. The experimental enthalpies were rationalized in terms of the standard enthalpy of transfer of solute from the aqueous to the micellar phase and of the distribution constant between the two phase. Information on the effect of the nature of the surfactant on the standard thermodynamic quantities of transfer(G _t ^o , H _t ^o , TS _t ^o ) is reported. The present data are compared to those previously reported for primary alcohols and the solubilizing properties shown by the different types of micelles are discussed.     

Thermodynamic properties of some N-alkyl-N-methylpiperidinium chlorides and N-alkylpiperidine hydrochlorides in water

Densities and heat capacities at 25°C were measured for N-octyl-, N-decyl- and N-dodecyl-N-methylpiperidinium chlorides and for N-octyl- and N-dodecylpiperidine hydrochlorides in water as functions of concentration. Enthalpies of dilution at 25°C and osmotic coefficients at 37°C of the N-methyl-N-alkylpiperidinium chlorides were also measured as functions of concentration. The partial molar volumes, heat capacities, relative enthalpies, nonideal Gibbs energies and entropies at 25°C were derived as functions of the surfactant concentration. By increasing the alkyl chain length of the surfactant, both the apparent molar volume vs. concentration curves are shifted toward greater values while the corresponding ones for the heat capacity are moved toward more negative values. These results are consistent with the higher hydrophobicity the longer the alkyl chain of the surfactant is. In the micellar region, the entropy and enthalpy vs. log m/m _cmc curves increase in a parallel manner by decreasing the alkyl chain length of the surfactant. Consequently, the negligible effect of the hydrophobicity of the surfactant on the Gibbs energy vs. log m/m _cmc trends is due to the enthalpy-entropy compensative effect. The thermodynamic functions of micellization were graphically evaluated on the basis of the pseudo-phase transition model. The absolute values of both the volume and heat capacity of micellization increase with an increasing number of carbon atoms in the alkyl chain (n _c ). The enthalpy and entropy of micellization vs. n _c are convex curves. Comparisons are also made between the present data and those of some alkylpyridinium chlorides reported elsewhere.     

Primärprodukte der Wasserphotolyse bei 1849 Å

Zusammenfassung Die Photolyse des Wassers bei 1849 Å wurde unter Verwendung von 0,01m-Formiat als Fänger für die H-Atome und OH-Radikale untersucht. Dabei diente 5m-Äthanol als Aktinometer mit einem korrigierten Wert für (H₂)=0,50. In diesem Fall wurde eine Quantenausbeute der Wasserphotolyse (H, OH)=0,36±0,01 bestimmt. Bezieht man die exper. Daten auf das N₂O-Aktinometer bei (–N₂O)=1,0, dann ist (H, OH)=0,29±0,01. In diesem Wert ist auch die Quantenausbeute der reaktionsfähigen angeregten Wassermoleküle, die mit Formiat reagieren, inbegriffen. Auf Grund von experimentellen Daten wurde ferner die Bildung von solvatisierten Elektronen (e ^–aq) vorgeschlagen. Durch Sättigung der Formiatlösung mit Kohlensäure, die sowohl vone ^–aq als auch von H₂O^* reduziert werden kann, wurde (e ^–aq, H₂O^*)>0,02<0,04 bestimmt.

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Liquid water photolysis at 1849 Å was investigated by using 0,01m-formate as scavenger for the H and OH radicals. 5M-ethyl alcohol serviced as actinometer with a corrected value of (H₂)=0,50. The quantum yield of water photolysis was determined in this case to be (H, OH)=0,36±0,01. When the experimental results are related to N₂O actinometer with (–N₂O)=1,0, a quantum yield of (H, OH)=0,29±0,01 is obtained. This value includes also the quantum yield of the excited water molecules which react with the formate. Based on experimental data the formation of solvated electrons (e ^–aq) is proposed. By saturation of the formate solution with carbon dioxide, which can be reduced bye ^–aq as well as by H₂O^*, (e ^–aq, H₂O^*>0,02<0,04 was determined.

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Volumes and heat capacities of water andN-methylformamide in mixtures of these solvents

The densities of mixtures ofN-methylformamide (NMF) and water (W) have been measured at 5, 15, 25, 35, and 45°C, and the heat capacities of the same system at 25°C, both over the whole mole-fraction range. From the experimental data the apparent molar volumes (_v) and heat capacities (_c) of NMF and of water are evaluated. The relatively small difference between the partial molar volumes or heat capacities at infinite dilution and the corresponding molar volumes or heat capacities of the pure liquids for both NMF and water suggests that with regard to these quantities replacement of a NMF molecule by a water molecule or vice versa produces no drastic changes. The partial molar volume of water at infinite dilution in NMF is smaller than the molar volume of pure water, but the corresponding partial molar heat capacity is unexpectedly high.     

Apparent molar volumes of aqueous calcium chloride to 250°C, 400 bars,and from molalities of 0.242 to 6.150

Relative densities of CaCl ₂ (aq) with 0.22ml(mol-kg^–1)6.150 were measured with vibrating- tube densimeters between 25 and 250°C and near 70 and 400 bars. Apparent molar volumes V calculated from the measured density differences were represented with the Pitzer ioninteraction treatment, with appropriate expressions chosen for the temperature and pressure dependence of the virial coefficients of the model. It was found that the partial molar volume at infinite dilution V ^o , and the second and third virial coefficients B ^V and C ^V , were necessary to represent V near the estimated experimental uncertainty. The ionic-strength dependent ^(1)v term in the B ^V coefficient was included in the fit. The representation for V has been integrated with respect to pressure to establish the pressure dependence of excess free energies over the temperature range studied. The volumetric data indicate that the logarithm of the mean ionic activity coefficient, ln ±(CaCl ₂ ), increases by a maximum of 0.3 at 400 bars, 250°C, and 6 mol-kg^–1 as compared with its value at saturation pressure.     

Enthalpies of solution and dilution of butanol and pentanol in dodecyltrimethylammonium bromide micellar solutions

The enthalpies of solution and of dilution of 1-butanol and 1-pentanol were measured in micellar solutions of dodecyltrimethylammonium bromide by systematically changing the concentration of alcohols and surfactant. The enthalpies of solution at infinite dilution of alcohols at each surfactant concentration were evaluated from a linear plot. This quantity increases with surfactant concentration (up to 0.8m) with a curvature which depends on the alcohol alkyl chain length. The difficulties arising for a quantitative treatment of both the enthalpies of dilution and of solution at finite alcohol concentrations are discussed. The dependence on the surfactant concentration of the standard enthalpies of solution and the enthalpies of dilution for m0 are rationalized. From the resulting equations the distribution constant, standard enthalpy of transfer, standard enthalpy of solution, and the alcohol-alcohol interaction parameter in the micellar phase are evaluated. The enthalpies of transfer obtained using this technique agree well with those previously reported from enthalpies of mixing. The distribution constants also agree with those reported in the literature from several approaches: mixing enthalpies, partial molar volumes, and the dependence of the cmc on added alcohol.     

Thermodynamics ofN,N,N-octylpentyldimethyl-ammonium chloride in water-urea mixtures

Specific conductivities, densities, heat capacities, and enthalpies of dilution at 25‡C were measured forN,N,N-octylpentyldimethylammonium chloride (OPAC) in water-urea mixtures at various urea concentrations m_u as functions of the surfactant concentration m_s. From conductivity data, the cmc and the degree of the counterion dissociation Β of the OPAC micelles were calculated. The cmc increases linearly with increasingm _u while Βvs. m_u is a smooth concave curve. From the experimental thermodynamic data, the apparentY _Φ and partialY ₂ molar properties (volumes, heat capacities, and relative enthalpies) are derived as functions of m_u andm _s . The effect of urea on the dependences of the different properties on m_s are discussed. From data in the premicellar region the standard partial molar volumesV ₂ ⁰ and heat capacitiesC _p2 ⁰ were evaluated. It was observed thatV ₂ ⁰ increases linearly withm _u whileC _p2 ⁰ decreases. The properties of OPAC in the dispersed and micellized forms at the cmc were obtained and, therefore, the thermodynamic functions of micellization were calculated on the basis of the pseudo-phase transition model.     

Thermodynamic properties and conductivities of some dodecylsurfactants in water

Densities, heat capacities, enthalpies of dilution, osmotic coefficients and conductivities are reported for dodecylamine hydrochloride, dodecyldimethylammonium and dodecyltrimethylammonium chloride in water over a wide range of concentration. The last two properties were also measured for dodecyltrimethylammonium bromide. From the thermodynamic data partial molar volumes, heat capacities and relative enthalpies and nonideal free energies and entropies were derived as a function of the surfactant concentration. The cmc's and degree of counterion dissociation were also calculated from the transport properties. It is shown that the trends of volumes, enthalpies, free energies and entropies are quite regular whereas heat capacities present maxima and minima at concentrations which depend on the nature of surfactants. Corresponding changes were observed in the osmotic coefficients and specific conductivities. The thermodynamic functions of micellization were evaluated on the basis of the pseudo-phase transition model. Finally, the effects of the introduction of methyl groups in the hydrophilic moiety of the surfactant and of the nature of the counterion on the thermodynamic properties of monomers and micelles are examined.     

Seawater—A test of multicomponent electrolyte solution theories. I. The apparent equivalent volume,expansibility, and compressibility of artificial seawater

The apparent equivalent volume _V, expansibility _E, and compressibility _K of an artificial seawater solution containing10 ionic components (Na⁺, Mg²⁺, Ca²⁺, K⁺, Sr²⁺, Cl^–, SO ₄ ^2– , HCO ₃ ^– , Br^–, and F^–) and one nonionic component (H₃BO₃) has been determined from0 to40°C (in5° intervals) and from0.1 to0.8 m ionic strength at1 atm. The concentration dependence (I_v=volume ionic strength) of the _V's, _E's, and _K's have been examined by using a Masson-type equation, = ^° +S'I _V ^1/2, and a Redlich-type equation, = ^° +SI _V ^1/2 +BI _V, where ^° is the infinite-dilution value, S is the empirical Masson slope, S is the theoretical Debye-Hückel slope, and B is an empirical deviation constant. By using Young's rule, = E_i(i), the apparent equivalent volumes, expansibilities, and compressibilities for sea salt have been estimated from the ionic and nonionic components making up the mixture. The estimated apparent molal quantities agree very well with the directly measured values providing the concentration terms, S _i and B_i, are weighted according to the methods of Wood and Reilly.Contribution Number 1599 from the University of Miami.     

Crystal structure and thermochemical properties of 1-dodecylamine hydrochloride (C12H28NCl)(s)

Crystal structure of 1-dodecylamine hydrochloride (C₁₂H₂₈NCl)(s) has been determined by an X-ray crystallography. Lattice potential energy and the molar volumes of the solid compound and its cation were respectively obtained. The enthalpy of dissolution of the compound was measured by an isoperibol solution-reaction calorimeter at 298.15 K. The molar enthalpy of dissolution at infinite dilution was determined to be , and relative apparent molar enthalpies (Φ_L), relative partial molar enthalpies (L₂) of the compound and relative partial molar enthalpies (L₁) of the solvent (double distilled water) at different concentrations m (mol kg⁻¹) were obtained through fitted multiple regression equation by means of Pitzer's theory. Finally, hydration enthalpies of the substance and its cation were calculated by designing a thermochemical cycle in accordance with lattice potential energy and the molar enthalpy of dissolution at infinite dilution .     

Thermochemistry of Amines: Experimental Standard Molar Enthalpies of Formation of N-Alkylated Piperidines

The standard molar enthalpies of formation _f H _m ^° (l) at the temperature T = 298.15 K were determined using combustion calorimetry for N-methylpiperidine (A), N-ethylpiperidine (B), N-propylpiperidine (C), N-butylpiperidine (D), N-cyclopentylpiperidine (E), N-cyclohexylpiperidine (F), and N-phenylpiperidine (G). The standard molar enthalpies of vaporization _l ^g H ^{m °} of these compounds were obtained from the temperature variation of the vapor pressure measured in a flow system. From these data the following standard molar enthalpies of formation in gaseous phase _f H _m ^° (g) were derived for: A –(61.39 ± 0.88); B –(88.1 ± 1.3); C –(105.81 ± 0.66); D –(126.2 ± 1.3); E ( –88.21 ± 0.75); F –(135.21 ± 0.94); G (70.3 ± 1.4) kJ · mol^–1. They are used to determine the strain enthalpies of the cyclic amines A–G. The N-alkylated piperidine rings have been found to be about strainless.     

VUV-Photolyse von Methanol bei 1236 Å

Zusammenfassung Es wird über die indirekte und die direkte VUV-Photolyse von luftfreiem Methanol in flüssiger Phase bei 1236 Å berichtet. Bei der Bestrahlung von wäßr. 0,01m-Methanol wurden folgende Produkte und Ausbeuten erhalten: (H₂)=1,00, (HCHO)=0,27, (CH₂OH)₂=0,12, (CH₂OH·CHO)=0,04 und (HCOOH)=0,02. Die Photolyse von flüssigem Methanol lieferte die gleichen Produkte, jedoch mit höheren Ausbeuten: (H₂)=1,50, (HCHO)=0,98, (CH₂OH)₂=0,28 und (CH₂OH·CHO)=0,06. Unter Anwendung von Methanol als Radikalfänger konnte auch die Quantenausbeute der Wasserphotolyse bei 1236 Å, (H,OH)=1,025 verifiziert werden. Wahrscheinliche Reaktionsmechanismen werden diskutiert.

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V.U.V.-Photolysis of methanol at 1236 Å

The indirect and the direct v.u.v.-photolysis of air free methanol in liquid phase at 1236 Å is reported. After irradiation of aqueous 0.01M-methanol the following products were obtained: (H₂)=1.00, (HCHO)=0.27, (CH₂OH)₂=0.12, (CH₂OH·CHO)=0.04 and (HCOOH)=0.02. The photolysis of liquid methanol yielded the same compounds, however with higher amount as follows: (H₂)=1.50, (HCHO)=0.98, (CH₂OH)₂=0.28 and (CH₂OH·CHO)=0.06. Using methanol as a scavenger for the H and OH radicals the quantum yield of the water photolysis at 1236 Å could be verified to be (H,OH)=1.025. Probable reaction mechanisms are discussed.

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Herrn Prof. Dr.E. Broda zum 60. Geburtstag gewidmet.     

Enthalpies of dilution for 1∶3 and 3∶1 electrolytes aqueous solutions

The enthalpies of dilution for aqueous solutions of [Co(cn)₃)]Cl₃, [Co(pn)₃)]Cl₃ and [Co(tn)₃]Cl₃, (whereen=1,2-diaminoethane,pn=1,2-diaminopropane, andtn=1,3-diaminopropane) have been measured at 298.15 K, and up to 1 mol kg^–1+, using a new large isoperibol calorimeter by the long-jump method. Relative apparent molar enthalpies,_291-01, have been extracted as an empirical equation relatingL andm. We have compared our complex salts with the 31 and 13 aqueous systems found in the literature. Theoretical predictions for 13 and 31 electrolytes in the Restricted Primitive Model are also shown.This work was supported in part by CICYT (M.E.C., Spain) under Research Project No.: PB92-0553.