Partial molal expansibilities of organic compounds in aqueous solution. I. Alcohols and ethers

The temperature dependence of limiting apparent molal volumes ° in water for some alcohols (methanol, ethanol, 1-propanol, 2-butanol, 3-pentanol, 3-hexanol, 2,5-hexanediol, cyclopentanol, cyclohexanol, cycloheptanol, and 1,4-cyclohexanediol) and ethers (trimethylene oxide, tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 1,3-dioxepane, 1,3,5-trioxane, dimethoxymethane, 1,2-dimethoxyethane, diethoxymethane, and diethyl ether) has been studied in the temperature range 10–50°C by means of an automatic digital-readout dilatometer. Values of the thermal expansion coefficient * = (1/°)(°/T)_p have been obtained at several temperatures and discussed together with literature data on expansibilities of related compounds. The data show a wide spectrum of values of ^* at low temperatures which is narrowed at the higher ones. The expansibilities of monofunctional alcohols increase with increasing temperature; the opposite effect is observed for polyhydric alcohols. The ^*'s of ethers are very slightly temperature dependent and are much higher, at low temperature, than those of alcohols having the same ratio ofn _o/n_c. These results are discussed in terms of solutewater interactions, and a possible interpretation is put forward.     

Apparent Molar Heat Capacities and Apparent Molar Volumes of Aqueous 1,1,1,3,3,3-Hexafluoroisopropanol at Different Temperatures

Specific heats and apparent molar heat capacities of aqueous 1,1,1,3,3,3-hexafluoroiso- proanol (HFIP) have been determined at temperatures from 20.0 to 45.0°C using micro differential scanning calorimetry in the molality range of 0.06741 to 1.24053 mol-kg^{– 1}. Densities and apparent molar volumes have also been determined for aqueous HFIP at temperatures from 10.3 to 30.0°C using digital densimetry in the molality range of 0.04009 to 0.67427 mol-kg^{– 1}. The results of these measurements have been used to calculate the following partial molar quantities and temperature derivatives for aqueous HFIP as a function of temperature: C_p,2,m°, (C_p,2,m°/T)_p, (²C_p,2,m°/T²)_p, V_2,m° and (V_2,m°/T)_p. The contribution of the — F atom to the partial molar heat capacity and volume has been calculated. The results have been explained in terms of structural changes in water in aqueous HFIP solution. The results obtained in this work contain essential information needed for the development of an equation of state for this system, when used in combination with other thermodynamic properties of aqueous HFIP.     

Apparent Molar Heat Capacities and Apparent Molar Volumes of Aqueous Nicotinamide at Different Temperatures

Specific heat capacities and apparent molar heat capacities of aqueous nicotinamide have been determined from 25.0 to 55.0°C using microdifferential scanning calorimetry in the molality range of 0.07433 to 1.50124 mol-kg^–1. Densities and apparent molar volumes have also been determined for aqueous nicotinamide from 10.30 to 34.98°C using a digital densimeter in the molality range 0.07804–2.02435 mol-kg^–1. The results of these measurements have been used to calculate the following partial molar quantities and temperature derivatives for aqueous nicotinamide as a function of temperature: C _p,2,m ^o, (C _p,2,m ^o/T)_p, (²C_p,2,m ^o/T ²)_p, V _2,m ^o, ( V _2,m ^o/T)_p, and (² V _2,m ²/T ²)_p. The results are discussed in terms of the changes in the packing of nicotinamide molecules in the crystal, interactions in the aqueous form, and its structure-promoting ability with rise in temperature.     

12-Membered crown ethers. Lipophilic derivatives of benzo- and naphtho-12-crown-4 and their membrane electrode properties. Crystal structures of benzo-12-crown-4 NaI and KI complexes

Lipophilic derivatives of benzo-12-crown-4 and naphtho-12-crown-4 have been synthesized. The behavior of the parent compounds and their derivatives in membrane ion-selective electrodes have been studied. Selectivity changes have been observed with the rise in lipophilicity. Crystal structures of the NaI and KI complexes of benzo-12-crown-4 (1 and2) have been determined by X-ray analysis. The alkali metal and iodide ions are in direct contact in2 but not in1. Compound1 [Na(benzo-12-crown-4)₂]·I is triclinic, witha=13.368(8),b=10.727(7),c=10.325(4) Å; =73.56(4),=77.73(4), =108.70(5)°;Z=2, space group is . Compound2 [K(benzo-12-crown-4)₂·I] is monoclinic, witha=15.807(8),b=12.043(4),c=15.601(6) Å,=117.74(3)°;Z=4, space groupC2/c. In both compounds the cations interact with all oxygen atoms of two crown ether molecules. Correlation of the crystal structures and behavior of the crown ethers in ion-selective membrane electrodes is discussed. Supplementary Data related to this article have been deposited with the British Library as Supplementary Publication No. 82185 (15 pages).     

Thermodynamics of nucleic acid bases and nucleosides in water from 25 to 55°C

Specific heat capacities, apparent molar heat capacities, densities, and apparent molar volumes have been determined for cytosine, uracil, thymine, adenine, cytidine, 2-deoxycytidine, uridine, thymidine and adenosine at temperatures from 25°C to 55°C. The results of these measurements have been used to calculate for the first time, the thermodynamic quantities:C _p,2 ^o , (C _p,2 ^o /T)_p, (² C _p,2 ^o T ²)_p,V ₂ ^o , (V ₂ ^o /T)_p, and (² V ₂ ^o /T ²)_p. The-CH₂-group contribution has been calculated at different temperatures. It has also been observed from the data for the nucleic acid bases and nucleosides that the additivity ruleC _p,2 ^o (nucleoside)-C _p,2 ^o (base) +C _p,2 ^o (water)=C _p,2 ^o (ribose) does not hold in these cases.     

Synthesis and electrochemical properties of amphiphilic crown ether langmuir-blodgett films [1]

4-Octadecanoylbenzo-15-crown-5 (I) and four 4-alkylbenzo-15-crown-5 ligands [4-XB15C5 where X =n-C₁₈H₃₇ (II), X =n-C₁₆H₃₃ (III), X =n-C₁₄H₂₉ (IV), and X =n-C₁₂H₂₅ (V)] have been synthesized. The -A isotherms ofI andII were systematically investigated. The results indicated that the Langmuir-Blodgett (LB) films have high stability where the ratios ofI/SA andII/SA were 1 : 1 and 1 : 10, respectively, with a 6.2 pH subphase. The LB films of the crown ethers were deposited onto graphite electrodes pretreated by immersing them in liquid wax. The peak current reached the maximum value when the electrode surface was modified with five layers of the amphiphilic crown ethers.     

Ion solvation in lithium battery electrolyte solutions. 1. Apparent molar volumes

Apparent molar volumes, V(MX), of seven electrolytes (NaClO₄, NaCF₃SO₃, NaBPh₄, LiClO₄, LiAsF₆, Ph₄AsCF₃SO₃ and KCF₃SO₃) have been determined by vibrating-tube densimetry in nonaqueous solvent mixtures of propylene carbonate (PC) with acetonitrile (AN), dimethoxyethane (DME) and tetrahydrofuran (THF). V(MX) was measured at an electrolyte concentration of 0.05M over the entire solvent composition range wherever possible. Ionic apparent molar volumes of transfer, _tV(ion), were obtained via the tetraphenylarsonium tetraphenylborate (TATB) assumption. _tV(ion) from PC to the mixed solvents are generally strongly negative for both cations and anions consistent with the greater compressibilities and lower dielectric constants of the cosolvents. In PC/AN mixtures cations and anions have similar values of _tV(ion) but in PC/DME and PC/THF mixtures they differ considerably. Cationic volumes show the expected dependence on ion-size but the differences among the anion volumes are much greater than expected at high cosolvent compositions. These effects are discussed in terms of preferential solvation and other solvent interactions. The implications of these findings for lithium batteries are briefly discussed.     

Volumetric Properties of Aqueous 2-Chloroethanol Solutions and Volumes of Transfer of Some Amino Acids and Peptides from Water to Aqueous 2-Chloroethanol Solutions

Densities and apparent molar volumes of aqueous 2-chloroethanol were determined at temperatures from 15.0 to 34.4°C using digital densimetry. The results of the volumetric measurements have been used to calculate the following thermodynamic quantites at 25°C: V ₂ ^o = 55.05 ± 0.02 cm³-mol^–1, (V ₂ ^o/T)_p = 0.01486 ± 0.00318 cm³-K^–1-mol^–1, and (² V ₂ ^o/T ²)_p = 0.02972 ± 0.00318 cm³-K^–2-mol^–1. Partial molar volumes of transfer from water to 1 mol-dm^–3 2-chloroethanol have also been determined for L-glycine, L-alanine, L-serine, L-glutamic acid, and L-aspartic acid at 35.0°C. The transfer results have been explained in terms of the nature of the interactions of the groups in the solute and solvent. Hydration numbers of L-glycine and L-alanine have also been calculated in aqueous 2-chloroethanol.     

Apparent molar heat capacities and volumes of electrolytes and ions in acetonitrile-water mixtures

Apparent molar volumes V and heat capacities C_p, of NaCl, KCl, KNO₃, AgNO₃, KI, NaBPh₄ and Ph₄PCl have been measured in acetonitrile (AN)-water mixtures up to x_AN=0.25 by flow densitometry and flow microcalorimetry. Limited data have also been obtained for NaF, LiCl and KBr up to x _AN =0.15. Single ion volumes and heat capacities of transfer were obtained using the assumption _tX(PH₄P⁺) = _tX(BPh₄-) where X=V or C _p and _tX is the change in X for a species on transfer from H₂O to AN-H₂O mixtures. Volumes and heat capacities for simple salts show relatively little dependence on solvent composition. However, _tX for simple ions show more pronounced variations, exhibiting at least one extremum. These extrema are similar to but much less pronounced than those derived previously for ions in t-butanol-water mixtures. Surprisingly little correlation is found between the present data and other thermodynamic transfer functions. This is attributed to the predominance of ion-solvent over solvent-solvent interactions in AN-H₂O solutions. _tV and _tC_p, for the silver ion differ markedly from those of the alkali metal ions as a result of the well-known specific interaction between Ag⁺ and AN.     

Reaction of H2PtCl6 with 18-crown-6 and dibenzo-18-crown-6 in 1,2-dichloroethane and acetonitrile

Compounds of the compositions [2(18-crown-6)6(H₂O)2(C₂H₄Cl₂){Pt²⁺(C₂H₄)}(Pt₂Cl₁₀)^2–], [4(18-crown-6)2(OH₃)⁺2(OH₂)2(NH₃)(Pt₂Cl₁₀)^2–], [(dibenzo-18-crown-6)6(H₂O){Pt²⁺(C₂H₄)}(Pt₂Cl₁₀)^2–], and [4(dibenzo-18-crown-6)2(OH₃)⁺2(OH₂)2(NH₃)Pt₂Cl₁₀)^2–] were prepared by reactions of H₂PtCl₆ with 18-crown-6 and dibenzo-18-crown-6.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1593–1599.Original Russian Text Copyright © 2004 by Guseva, Busygina, Khasanshin, Polovnyak, Yarkova, Yusupov.This revised version was published online in April 2005 with a corrected cover date.     

Isentropic compressibilities of univalent electrolytes in methanol at 25°C

A flow densimeter and an ultrasonic sound velocimeter have been used to measure densities and isentropic compressibilities of solutions of LiBr, NaCl, NaBr, Nal, KF, KCl, KBr, Kl, RbBr, Rbl, CsF, CsBr, Ph ₄ PBr, and NaBPh ₄ in anhydrous methanol at 25°C. the latter two electrolytes were also investigated in water at 25°C. Concentrations ranged from about 0.005 m to above 0.25m, solubility permitting. Apparent molar isentropic compressibilities, K_S,, have been calculated and extrapolated to infinite dilution to obtain K _S, ^o . The K _S, ^o values in methanol are all negative, and significantly more negative than the corresponding data in water. Additional data from the literature for acetonitrile and ethanol solutions show that K _S, ^o for the alkali metal halides become more negative in direct proportion to increasing solvent isentropic compressibility. Furthermore, the dependence of K _S, ^o in ionic size also varies in proportion to solvent isentropic compressibility. An explanation of this behavior is presented.     

Thermodynamic Properties of Aqueous Dimethylamine and Dimethylammonium Chloride at Temperatures from 283 K to 523 K: Apparent Molar Volumes, Heat Capacities, and Temperature Dependence of Ionization

Data for the apparent molar volumes of aqueous dimethylamine and dimethylammonium chloride have been determined with platinum vibrating tube densimeters at temperatures 283.15 K T 523.15 K and at different pressures. Apparent molar heat capacities were measured with a Picker flow microcalorimeter over the temperature range 283.15 K T 343.15 K at 1 bar. At high temperatures and steam saturation pressures, the standard partial molar volumes of dimethylamine and dimethylammonium chloride deviate towards positive and negative discontinuities at the critical temperature and pressure, as is typical for many neutral and ionic species. The revised Helgeson-Kirkham-Flowers (HKF) model and fitting equations based on the appropriate derivatives of solvent density have been used to represent the temperature and pressure dependence of the standard partial molar properties. The standard partial molar heat capacities of dimethylamine ionization , calculated from both models, are consistent with literature data obtained by calorimetric measurements at T 398 K to within experimental error. At temperatures below 523 K, the standard partial molar volumes of dimethylamine ionization agree with those of morpholine to within 12 cm³-mol^-1, suggesting that the ionization of secondary amine groups in each molecule is very similar. The extrapolated value for of dimethylamine above 523 K is very different from the values measured for morpholine at higher temperature. The difference is undoubtedly due to the lower critical temperature and pressure of (CH₃)₂NH(aq).     

First and second thermodynamic mixing properties of ethylbenzene +n-alkanes: Experimental and theory

Isobaric expansibilities _P and isothermal compressibilities _T have been determined at 25 and 45°C for binary mixtures of ethylbenzene + n-tetradecane and + n-hexadecane and the corresponding excess functions (V ^E /T)_P and (V ^E /P)_T have also been obtained. With these data and supplementary literature values, the following second order mixing properties are also reported at 25°C: _S ^E , (V ^E /P)_T, C_V and (VT). All mixing quantities have been compared with the results obtained at 25°C by using the Prigogine-Flory-Patterson theory of liquid mixtures. The predicted values suggest that the ability of ethylbenzene as a breaker of the pure n-C_n orientations is similar to what we found for toluene and higher than for p-xylene.     

A molecular mechanics study of the selectivity of crown ethers for metal ions on the basis of their size

A molecular mechanics (MM) analysis is carried out on complexes of crown ethers CH₂(OCH₂CH₂)_nCH₂O, 12-crown-4 (n=3), 15-crown-5 (n=4), 18-crown-6 (n=5), 24-crown-8 (n=7), and 30-crown-11 (n=9) to determine the nature of the selectivity shown by these ligands for metal ions on the basis of metal ion size. The MM program used is SYBYL, and M-O bonds are represented using a covalent model, i.e. the M-O bonds are modelled with ideal M-O bond lengths and force constants. The previously used technique of calculating strain energy as a function of M-O bond length is used for all the complexes, and also the complexes of the non-macrocyclic polyethylene glycol analogues. It is concluded that the crown ethers fall into three groups with regard to selectivity for metal ions. Group one consists of the smaller macrocycles such as 12-crown-4 and 15-crown-5, where metal ions generally are too large to enter the cavity of the macrocycle, and the metal ion is coordinated lying outside the plane of the donor atoms of the ligand. Here factors that control selectivity are the same as in non-macrocyclic ligands, chiefly the size of the chelate ring. Group 2 contains only 18-crown-6 of the ligands studied here. 18-Crown-6 complexes have three important conformers, one of which, theD _3d , shows sharp size match selectivity, preferring metal ions with M-O bond lengths of about 2.9 . The other two conformers are adopted by metal ions too small for theD _3d conformer, and are more flexible, exerting little size-match selectivity. These other two conformers are of higher energy than theD _3d conformer for metal ions with M-O bond lengths greater than 2.55 . Thus, a genuine size match selectivity is found for K⁺ with 18-crown-6. With an ideal M-O bond length of 2.88 , K⁺ fits the cavity of theD _3d conformer of 18-crown-6 very closely. The third group consists of very large macrocycles such as 24-crown-8 and 30-crown-10. These enfold the metal ion in extremely folded conformations, but may, as does 30-crown-10, exert considerable selectivity for metal ions on the basis of their size by virtue of the conformation resulting in a set of torsional angles in the ring atoms of the macrocycle which confer considerable rigidity on the ligand.     

Synthesis of formyl derivatives of benzodiazacrown ethers and benzocryptands

A simple and convenient procedure was developed for the synthesis of formyl derivatives of benzodiazacrown ethers and benzocryptands by condensation of 3,4-bis(2-iodoethoxy)benzaldehyde with ,-oligooxaalkanediamines or diazacrown ethers in the presence of alkali metal carbonates under high-dilution conditions in various organic solvents and their mixtures with water. In the reactions giving rise to diazacrown ethers, alkali metal cations exhibit the negative template effect resulting in a decrease in the yield of the target product if the size of the cation matches well the size of the cavity of the crown ether formed. An N,N"-bis(carboxymethyl) derivative was prepared from the formyl derivative of benzodiaza-18-crown-6.     

Applications of evolved gas analysis to the study of inorganic materials and processes

The value and versatility of evolved gas analysis (EGA) are described by the use of selected recent examples. Three particular attributes of EGA methods are stressed. The first, specificity, reveals the frequent necessity of using EGA to substantiate conclusions based upon other thermal analytical techniques e.g. thermogravimetry (TG) or differential thermal analysis (DTA). To this end, the weaknesses of other thermal analytical techniques for the analysis of asbestos is reveladed by EGA. However, because of EGA's specificity it could be used for this purpose. Second, sensitivity, is demonstrated by use of mass spectrographic EGA techniques to study the kinetics of the early stages for the thermal decomposition of InP. This is further illustrated by qualitative assessments of the effects of various films in contact with the InP upon its thermal decomposition. A third advantage of EGA, insensitivity to experimental perturbations arising from an external magnetic field gradient, allows for its use to study the effects of such field gradients with less ambiguity than occurs with TG or DTA. This is shown for studies of the reduction of NiO, Fe₂O₃, and Co₃O₄ by H₂.

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Zusammenfassung Die Bedeutung und die Vielseitigkeit der EGA wird anhand ausgewählter neuerer Beispiele beschreiben. Drei besondere Merkmale der EGA-Methoden werden hervorgehoben. Die erste, die Spezifität, wird der häufigen Notwendigkeit zur Anwendung der EGA gerecht, um auf andere thermische Analysentechniken, z.B. auf TG oder DTA beruhende Schlussfolgerungen zu stützen. Dies wird demonstriert, indem gezeigt wird, dass die EGA die Unzulänglichkeiten anderer thermischer Verfahren zur Analyse von Asbest in Erscheinung treten lässt und infolge ihrer Spezifität für diesen Zweck geeignet ist. Das zweite Merkmal, die Empfindlichkeit, wird durch Anwendung der massenspektrographischen EGA-Technik zur Untersuchung des frühen Stadiums der thermischen Zersetzung von InP demonstriert. Dies wird weiter durch qualitative Beurteilung der Wirkungen von verschiedenen in Kontakt mit dem InP befindlichen Filmen auf dessen thermische Zersetzung illustriert. Ein dritter Vorteil der EGA is deren Unempfindlichkeit gegenüber von äusseren magnetischen Feldgradienten herrührenden experimentellen Störungen, wodurch diese Methode bei der Untersuchung der Wirkungen solcher Feldgradienten eindeutigere Ergebnisse als die TG oder DTA liefert. Dies wird anhand von Untersuchungen der Reduktion von NiO, Fe₂O₃ und Co₃O₄ mit H₂ gezeigt.

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//, . , , , : , , . . , - InP. , In P . , . . , .

     

Apparent molar heat capacities and volumes of electrolytes and ions int-butanol-water mixtures

The apparent molar volumes V and heat capacities C _p, of NaCl, LiCl, NaF, KI, NaBPh₄ and Ph₄PCl have been determined in solutions of H₂O containing up to 40 mass% t-butyl alcohol (TBA) by flow densitometry and flow microcalorimetry. Combination of these results with literature data allows calculation of V and C _p, for 16 ions in these mixtures using the assumption that _tX(Ph₄P⁺) = _tX(BPh ₄ ^– ) where X=V or C _p and _tX is the change in X for a species on transfer from H₂O to TBA-H₂O mixtures. These are the first reported single ion values for C _p, in a mixed solvent. While whole electrolyte volumes and heat capacities show relatively smooth changes with solvent composition, _tX(ion) exhibit two well-developed extrema at around 10 and 25 mass% TBA. The shape of the _tX(ion) curves shows considerable uniformity among the alkali metal cations and the halide ions but the extrema become more pronounced with increasing size among the tetraalkylammonium ions. These extrema are analogous to those observed in aqueous organic mixtures of surfactants and are probably indicative of microphase transitions in these strongly interacting solvent mixtures.     

PVT properties of concentrated aqueous electrolytes. II. Compressibilities and apparent molar compressibilities of aqueous NaCl,Na2SO4, MgCl2, and MgSO4 from dilute solution to saturation and from 0 to 50°C

The relative sound velocities (U-U°) of aqueous NaCl, Na₂SO₄, MgCl₂, and MgSO₄ solutions were measured from 0.05m to saturation and from 0 to 45°C. The sound speeds were combined with our earlier work and fitted to a function of molality and temperature to standard deviations within 0.3 m-sec^–1. The adiabatic compressibilities, _s, were determined from the sound speeds and used to calculate adiabatic apparent molar compressibilities, K_,s, isothermal compressibilities, , and apparent molar compressibilities, K, were determined from the adiabatic values using literature data for expansibilities and heat capacities. The values of K have been extrapolated to infinite dilution using an extended limiting law. The resulting K⁰ at various temperatures are in reasonable agreement with literature values. The results of this study have been combined with our earlier results to derive a secant bulk modulus equation of state for NaCl, Na₂SO₄, MgCl₂, and MgSO₄ solutions valid from 0 to 50°C and 0 to 1000 bar.     

Molecular dynamics and the structure of macrocycles —Solvent acetonitrile interactions

Microwave complex permittivities,* = -J, are reported in the 1–90 GHz frequency range for the macrocycles 18-crown-6 (18C6) and 15C5 added to acetonitrile in stoichiometric proportions, in the solvent CCl₄ at 25°C. Digitized infrared spectra of the CN stretch ₂ vibration of acetonitrile for the same systems are reported in the 2300–2200 cm^–1 spectral region. The macrocycle 12C4 added to CH₃CN has also been investigated in the infrared. Both the dielectric relaxation and infrared results are interpreted in terms of macrocycle-acetonitrile interactions, probably involving a methyl-hydrogen to ethereal-oxygen interaction. These interactions with CH₃CN diminish in strength according to the sequence: 18C6 > 15C5 > 12C4.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Fällungsanalyse im Mikrogrammbereich: Eine neue Methode

Zusammenfassung Eine neue Methode zur Durchführung gravimetrischer Bestimmungen im Mikrogrammbereich wurde beschrieben; diese beruht im wesentlichen darauf, daß der Niederschlag nicht mehr zusammen mit dem Filter, sondern nach Überführen mit einem geeigneten Lösungsmittel in einem separaten Wägegefäß gewogen wird.Die dazu nötigen Geräte und deren Herstellung wurden beschrieben. Nach dieser Methode wurden folgende Bestimmungen mit zufriedenstellender Richtigkeit durchgeführt: 2,5–25g Al, 5–50g Cu und 5–50g Zn mit Oxin, 2,5–25g Fe(III) und 2,5–25g Ti(IV) mit N-Benzoyl-phenylhydroxylamin, 5–50g Ni und 5–50g Cu mit Salicylaldoxim, 2,5–50g Co(II) und 2,5–50g Fe(III) mit -Nitroso--naphthol sowie 5–50g Chlorid als Silberchlorid.

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Precipitation analysis in the microgram-scale: A new method

Summary A new method for gravimetric determinations in the microgram-scale is described. This method is based on the fact that the precipitate is not weighed together with the filter but is transferred to a separate weighingvessel using a suitable solvent. The necessary simple devices and their use are described. The following determinations were carried out with satisfying accuracy: 2,5–25g Al, 5–50g Cu and 5–50g Zn with Oxine, 2,5–25g Fe and 2,5–25g Ti withN-benzoylphenylhydroxylamine, 5–50g Ni and 5–50g Cu with salicylaldoxime, 2,52–50g Co and 2,5–50g Fe with -nitroso--naphthol and 5–50g chloride as silver chloride.