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Aims: This field experiment aimed to investigate the effect of using foliar treatments and applying different fertilizers on wheat (TriticumaestivumL.) growth, productivity, and soil fertility under arid conditions. Background: Agriculture is a critical socio-economic sector in Egypt, generating approximately 10 to 15% of the national gross domestic product. Abiotic stresses arising from climate change negate crop growth and yield, leading to food insecurity. Methods: Six treatments were carried out in the order: CK (control without amendment); NPK (mineral fertilizer: mineral fertilizers, 38 g/m2 of urea (46% of N), 10 g/m2 of calcium phosphate (45% of P2O5), 12 g/m2 of potassium sulfate (50% of K2O)); Azospirillum brasilense (Az), bacteria were soaked with the seeds for 4 hours before sowing and introduced three-time into the soil with irrigation water at 0.7 ml/m2; vermicompost (VC) applied to the soil (2.5 kg/m2); humic substances (0.5 ml/m2) for foliar inoculation (HS); HS + micronutrients (HS-M) soil application (1 ml/m2) with irrigation water. All treatments were applied as soil additives and foliar spray to wheat plants at 31±1 °C for the first two months from seed sowing in calcareous soil. Analysis of variance (ANOVA) of experimental data showed the significance of positive effects of all treatments on soil fertility and plant growth compared to the control and NPK treatments. Results: The HS and VC treatments had positive effects on the development of plant nutrition, wheat growth, soil pH, and plant availability of micronutrients, which was also reflected in the wheat grain yield and water use efficiency. It was also evident that treating the plants and soil with HS-M increased wheat yield from 3.45 to 8.97 t ha-1 (260%) compared to the control. On the other hand, VC and Az treatments increased the grain yield by 278% and 267%, respectively, compared to control and NPK treatments. The water use efficiency (kg grain / m3) values increased by 279, 268, 262, 258, and 139% for HS-M, HS, VC, Az, and NPK treatments, respectively, compared to CK. The plants' total N, P, and K content were higher with all organic and biological treatments than NPK and control. Conclusion: This study has shown that the HS, Az, VC, and HS-M soil additives and foliar applications significantly (p ≤ 0.05) increased the status of Fe, Zn, Mn, Cu, and B in soil, plant growth rate, grain yield, 1000 grain weight, water use efficiency, and soil macro-nutrient of wheat plants growing on calcareous soil.

In Egypt, the total area of agricultural land is 3.36 million acres, which is 3.8% of the country entire territory. One of the main obstacles to agricultural production in Egypt is soil salinizatio...

Environmental pollution is becoming one of the most important global problems. Understanding the main factors affecting accumulation of toxic trace elements in consumed crops is of particular value. Unfortunately, possible toxicity of many trace elements is still poorly studied. The development of measures on identification of new potentially toxic trace elements is critical for high quality and safety of food. In the research, we performed greenhouse pot experiments with two major crops, wheat and barley, that were grown in the soil contaminated with bromides of ammonium and neodymium. The concentrations of elements in the plants and soil were determined by ICP-MS/ICP-OES after leaching the samples with tetramethyl ammonium hydroxide. Additionally, variations in the biomasses and concentrations of pigments in the plant leaves were studied. Although wheat and barley are botanically similar and were grown under the same conditions, concentrations of several elements in the plants were rather different. Both wheat and barley were capable of accumulating high concentrations of bromine (Br) when the plants grow in the soil contaminated with this trace element, but demonstrated different response on the soil contamination. The Br concentrations were always higher in barley, while the concentrations of pigments in barley leaves were lower than in leaves of wheat. During first days, biomass of the plants grown in the soil contaminated with bromides was slightly lower than biomass of the wheat and barley grown in uncontaminated soil. However, with time the bromides exhibited positive effect on the plant biomass.

Aims: The aim of this study was to determine and monitor the influences of organic and biological additives compared to mineral fertilizers on leaching characteristics of anions and cations, also to know more about the ability of these additives to make complexes with dissolved and toxic salts to decrease soil salinity. Background: Salt-affected soils comprise of saline and sodic soils which differ in origin, physico-chemical properties and the constraints to plant growth. Due to the presence of excess soluble salts (e.g. sodium (Na+) and chlorides (Cl-)). Methods: Ten treatments were established, including two levels of spent grain (environmental organic wastes from the beer industry), S1(10 g of spent grain / kg soil) and S2 ( 20 g of spent grain / kg soil); two levels of compost M1(10 g of compost / kg soil) and M2 ( 20 g of compost / kg soil); mixed M1 with S1 (M1S1); inoculation of Azospirillum brasilense (A1); inoculation A1 with S2 (A1S1); inoculation A1 with M1 (A1M1); 20:20:20 of N, P, and K fertilizers (NPK), and control (CK, without any additives). All treatments were mixed with 30 kg soil pots under greenhouse conditions, corn (Zea mayz L.) seeds were sown in the soil pots. The most relevant nitrogen and salt in soil leachates were collected and analysed every 20 days for 100 days. The soil leachates were collected under plant growth from pots by closed system. Results: The result revealed that organic additives such as A1 and S2 treatments effectively decreased soil pH, soil EC, and reduced NaCl concentration in soil leachates. The Ca2+ and K+ cations in the soil leachates were not stable at high levels of organic additives. Soluble NO3- and NH4+ were significantly lower in A1, S2, and A1S1 treatments than in NPK, M2, and CK treatments. Soil treatment with A1 and S2 significantly improved the soil chemical environment by increasing the Cation Exchange Capacity (CEC) and soluble and exchangeable-K+ and thus limited entry of Na+ into the exchange complex in soil and consists complex with soluble Na+ as sodium humate form. Conclusion: In the final, the highest nitrogen use efficiency with the least NO3- and NH4+ losses in saline-sodic soil was also found in S2 and A1 treatments. Moreover, under this bio-organic fertilization way, NO3- concentrations in soil leachates was outside of danger of damaging the environment. Thus, spent grain with Azospirillum were suggested to be the optimal fertilizer with the lowest nitrogen leaching losses, best yield, quality, and the least groundwater environmental risk under corn (Zea mays L.) organic and bio-organic cultivation comparing with chemical cultivation.

In this work, using an example of using current leads of different designs, the process of interaction of an electrolyte-plasma discharge with the surface of a metal anode at atmospheric pressure, at an incoming electrolyte temperature of 4–90 ℃ in the operating voltage range of 20 ℃ –500 V, with an interelectrode gap of 2–30 mm and a volumetric flow rate of electrolyte 2–90 l/h. It is shown that the surface morphology when interacting with an electric discharge varies over a wide range from a polished surface with a roughness parameter Ra of 0.034 μm to critical surface destruction by arc electric discharges. The results obtained make it possible to classify the discharges obtained as glow, spark, microarc, and arc discharges. The use of these discharges allows them to be used to create a technology for processing such complex products as coronary stents and turbine blades.

Locomotor activity requires fine balance control that strongly depends on the afferent input from the load receptors. Following hindlimb unloading (HU), the kinematic and EMG activity of the hindlimbs is known to change significantly. However, the effects of HU on the integrative control mechanisms of posture and locomotion are not clear. The goal of the present study was to evaluate the center of mass (CoM) dynamic stabilization and associated adaptive changes in the trunk and hindlimb muscle activity during locomotion after 7 days of HU. The EMG signals from the muscles of the low lumbar trunk [m. longissimus dorsi (VERT)] and the hind limb [m. tibialis anterior (TA), m. semitendinosus (ST), m. soleus (SOL)] were recorded together with the hindquarter kinematics during locomotion on a treadmill in six rats before and after HU. The CoM lateral shift in the step cycle significantly increased after HU and coincided with the enhanced activity of the VERT. The mean EMG of the TA and the ST flexor activity increased significantly with reduction of their burst duration. These data demonstrate the disturbances of body balance after HU that can influence the basic parameters of locomotor activity. The load-dependent mechanisms resulted in compensatory adjustments of flexor activity toward a faster gait strategy, such as a trot or gallop, which presumably have supraspinal origin. The neuronal underpinnings of these integrative posture and locomotion mechanisms and their possible reorganization after HU are discussed.

The descriptive ability of two integral biotic indices obtained from laboratory experimental data focused on estimating the effects of humic products (HPs) on the microbiota under conditions of copper contamination in a model soil substrate is evaluated. The “Standard Soil” prepared from sand, kaolin, and peat (ISO 11268-1) as recommended for the assessment of biological effects was used. To summarize the results of ecotoxicological studies of Cu-polluted samples (660 mg Cu/kg) and to provide the integral estimation of HPs impact on the microbiota, two statistical models were used: the Harrington’s desirability function D and the integrated parameter of the soil microbial system sustainability G (ratio of biodiversity to instability) using multisubstrate testing. The indices obtained based on two sets of multidimensional data were compared in their descriptive ability when estimating the detoxifying efficiency of HPs. It was found that HPs mainly stimulate multispecies bacterial complexes, while the test cultures representing higher plants and algae are less sensitive to their impact. Three of the five studied HPs showed a pronounced detoxifying effect and improved the state of the studied system. Both integral biotic indices—the generalized Harrington desirability function D and the General sustainability parameter of the system G—demonstrated a similar effect vector. For the purpose of environmental regulation, the use of the integrated approach based on a generalized desirability function could be recommended due to its higher completeness and reliability of the system of biotic indicators.

Landscape response to Late Holocene climatic cycles is based on detailed hierarchical morphological, analytical and micro-biomorphic research of a soil chronosequence which included a soil buried under a fortification earth wall of the Early Iron Age (Luvic Chernozem) and a surface soil (Chernic Greyzemic Luvic Phaeozem) in the southern forest-steppe area of the East European Plain. Both soils formed on similar surfaces with the same lithology (non-carbonate loess underlain by carbonate loess), at the same elevation, and in close proximity to each other. The buried soil was truncated by at 40 cm and transformed by diagenesis. Taking this into account it was possible to reconstruct the soil formed by the time of burial under the earth wall and to classify it as (Chernic) Luvic Phaeozem. Both surface and buried soils are polygenetic combining the features of humid (forest?) and steppe pedogenesis. The radiocarbon data obtained from the Humic horizon of the buried soil (6750 ± 120 years CalBP) allows bracketing the steppe environment to the mid-Holocene (Atlantic period). Pedogenetic evolution since the Early Iron Age included the next stage of clay illuviation (formation of thin hypo-coatings.) and the development of Greyzemic features. The studied Phaeozems indicate relative landscape stability at the southern boundary of the forest-steppe zone.

The article presents the results of experimental data on the formation of thin layers of the surface of stainless steels by jet focused electrolyte-plasma treatment. An experimental electrolyte-plasma installation is shown, which makes it possible to remove the thinnest layers from the surface of samples using an electrolyte-plasma discharge. In the work, hollow and type-setting current leads were used. The surface roughness parameters during the processing of samples from 08X18H9T, AISI 304, and HVG stainless steels are studied. Samples with a low level of surface roughness were obtained. A decrease in the mass of samples after electrolyte-plasma treatment is shown. The minimum removal of metal from the surface of the samples was recorded. The theoretical regularities of the formation of the surface layer geometry are considered. The results of the work can be applied to metallurgical, machine-building or turbine production.

In Egypt, the total area of agricultural land is 3.36 million acres, which is 3.8 % of the entire territory of the country. One of the main obstacles to agricultural production in Egypt is soil salinization and degradation. Therefore, saline-sodic soil reclamation in arid regions is highly relevant. This study aimed to use Azospirillum inoculation with eco-friendly organic wastes for free remediation of saline-sodic soils. In this work nine treatments included two levels of spent grain (S1 and S2), two levels of compost (C1 and C2), a mix of both sources (C1S1), one level of Azospirillum (A1), a mix of both sources with Azospirillum (A1S1 and A1C1) and an untreated control. The treatments were previously incubated with soil at field capacity for five months under laboratory conditions at 28 °C. The most relevant chemical and biological parameters were analysed every month for five months. Results indicate that Azospirillum inoculation with spent grain increased soil organic carbon (SOC), dehydrogenase and urease enzymes, micro-nutrients (Fe2+, Zn2+, Mn2+, Cu2+ and B+), and macro-nutrients (N, P and K); while decreased exchangeable sodium percentage (ESP), pH and EC, by 75 %, 12 %, and 43 % respectively, compared to initial conditions. The significant variation was observed in chemical and biological properties among all treatments in the order of S2 > A1S1 > A1 > C2 > C1S1 > A1C1 > C1 > control. In conclusion, the addition of Azospirillum with spent grain is highly recommended for amelioration of the saline-sodic soil and is more effective compared with compost to remediate saline-sodic soils.

Lower nitrogen use efficiency is major crop productivity limiting factor in semi-arid regions due to its poor organic contents in the soil; our research work is considered to optimize crop productivity by soil and plant chem-biological correction. This study designed and aimed to use soil inoculation with plant growth-promoting rhizobacteria of the genus Azospirillum and foiler application by humic preparations ALCRI-CropHelp and ALCRI-CropHelp-M compared with control and NPK fertilizer under wheat plants in arid regions of Egypt. Experimental data showed that biological correction contributed to a significant increase in wheat yield in the arid regions. The specific results for Azospirillum, ALCRI-CropHelp, and ALCRI-CropHelp-M were significantly increased wheat grain yield on 256, 267, and 278 % relative to the control, respectively. Simultaneously, water use efficiency has increased by more than 2.5 times, compared with control and NPK treatments. This effect was achieved due to multiple effects on the metabolism of agricultural plants, and applications of ALCRI-CropHelp and ALCRI-CropHelp-M treatments revealed an increase in the biological yield, spike length, harvest index compared with control and NPK treatments. In conclusion, this study has shown that the ALCRI-CropHelp Az and ALCRI-CropHelp-M foliar applications significantly (P

The need for cheap and affordable alternate sources of plant nutrient inputs to boost the nutrient level of degraded arable farmlands has been a major concern for soil scientists, agronomists, and local farmers. In 2018, a greenhouse and laboratory pot experiment was carried out under control conditions for 21 weeks to evaluate the effect of plant growth-promoting rhizobacteria (Azospirillium brasilense), spent grain (SG) organic wastes from the beer industry, and chemical fertilizer (CF) on the soil fertility–plant nutrition, corn (Zea Mays L.) germination rate in calcareous soil. The treatments consisted of CK (control), SG (spent grain, 20 g kg−1 soil), Az (Azospirillium seed inoculation), CF (100% of NPK recommended fertilizers), bio-organic (Az with SG), bio-mineral (Az with CF), and organo-mineral (50% of SG +50% of CF). These treatments were arranged in a randomized complete block design and replicated three times. Results showed that after 10 and 21 weeks, SG application significantly increased soil organic carbon by 69% and 67.8%, total nitrogen (TN) by 87.66% and 85.44%, and raised available P (P) by 75.7% and 87.23%, respectively. The final germination percentage (FGP), germination index (GI), coefficient of velocity of germination (CVG) and plant height were significantly higher in the amended pots than that of the control pots after 21 days of planting. The SG with Az treatments had the highest GI, CVG, and FGP of 9.23, 0.19 day−1, and 100 %, respectively, while the least values were obtained in the CF 2.37, 0.12 day−1, and 61.6%, respectively. The highest values of N/P ratio, available Fe2＋, Zn 2 + , and Mn 2 + were 401, 20.35 mg kg−1, 7.27 mg kg−1, and 16.58 mg kg−1 respectively, as well as bio-fertilizers enhanced the dehydrogenase and urease enzymes by 1117.3 μ g TPF ml−1, and 275.4 mg NH 3 − Hg−1h−1 respectively, after 21 weeks of seed sowing. The final results among all treatments were in the order of SG > Bio-organic > Az > Organo-mineral > Bio-mineral > CF > CK. In conclusion, the application of SG and Az is recommended to improve TN and P use efficiencies, micro-nutrients uptake, plant seed germination performance of maize, and enhancement of calcareous soil properties.

The study focused on investigating the contribution of reclamation strategies of saline-sodic soils and their impacts on soil fertility characteristics. In this study, the soil treatments were denoted as: SG1 and SG2 (23.8 and 47.7 ton/ha of spent grain); TC1 and TC2 (23.8 and 47.6 ton/ha of compost); Azospirillium in inoculation with seed and soil (Az); Az + SG1 (Az+SG1); Az + TC1 (Az+TC1); mineral fertilizers (NPK); and control (CK). All treatments were mixed in pots with 30 kg soil. The results showed that reclamation with Az and SG2 treatments significantly affected soil pH, EC, and macronutrients. In contrast, no significant (P > 0.05) effects were found with the two compost levels and NPK treatments. The salt contents were maximal in the control treatment, while decreased with Az, SG2, and Az+SG treatments. However, SG2 application decreased the soluble Na+ concentrations in soil solution. The effect of organic and biological reclamations on chemical properties was in the following order: Az+SG > SG2 > Az > TC2 > Az+M > SG1 > TC1 > NPK > CK. Moreover, it positively impacted the salt contents, which improved soil chemical properties in the saline-sodic soil after three months of seed sowing in the greenhouse.

The method of chemodestructive fractionation is suggested to assess the composition of soil organic matter. This method is based on determination of the resilience of soil organic matter components and/or different parts of organic compounds to the impact of oxidizing agents. For this purpose, a series of solutions with similar concentration of the oxidant (K2Cr2O7), but with linearly increasing oxidative capacity was prepared. Chemodestructive fractionation showed that the portion of easily oxidizable (labile) organic matter in humus horizons of different soil types depends on the conditions of soil formation. It was maximal in hydromorphic soils of the taiga zone and minimal in automorphic soils of the dry steppe zone. The portion of easily oxidizable organic matter in arable soils increased with an increase in the rate of organic fertilizers application. The long-lasting agricultural use of soils and burying of the humus horizons within the upper one-meter layer resulted in the decreasing content of easily oxidizable organic matter. It was found that the portion of easily oxidizable organic matter decreases by the mid-summer or fall in comparison with the spring or early summer period.

Based on analyzing the catenary sequence of soils and parent materials down the northern slope of the Klin-Dmitrov Ridge adjacent to the Upper Volga Lowland (formerly the periglacial zone of the Russian Plain), it was revealed that sediments including sandy loams, clay loams and clays, which constituted slope terraces at heights from 130 to 180 m a.s.l. and often accounted for lithic discontinuities in soil profiles, had glacio-lacustrine genesis, i.e., they had accumulated during the existence of a periglacial dammed lake at the final stages of the Late Pleistocene.

The primary solvation sphere surrounding the thiocyanate or the selenocyanide anion in protic solvents, such as methanol, N-methylformamide and formamide, forms intimate hydrogen bonds with these anions. These interactions perturb the electron density and vibrational modes of these anions and can therefore be studied by NMR and infrared spectroscopies. In neat solutions, these solvents form hydrogen bonds to the nitrogen end along the molecular axis and nonaxially to the π cloud of the C−N bond, although a substantial proportion of the anions is not hydrogen bonded. In nitromethane solutions, the thiocyanate and selenocyanide anions form weak complexes with methanol and the amide solvents (K < 1 M-1), which is an order of magnitude smaller than that of OCN- with the same solvents, determined in our previous investigation of the cyanate anion. The remarkable differences in the solvation of these singly charged anions can be understood by theoretical calculations of their electrostatic potentials.

The structures for Na+(12-crown-4)2SCN- and Na+(12-crown-4)2SCN-·HOMe have been determined by X-ray crystallography. In the crystalline solvate, the methanol molecule forms a nonaxial hydrogen bond to the nitrogen atom of thiocyanate anion. This uncommon hydrogen bonded structure markedly affects the frequency of the νCN vibration, which is lowered with respect to the unperturbed anion in Na+(12-crown-4)2SCN-. Theoretical studies of SCN-·HOMe complexes also predict that nonaxial hydrogen bonds lower the frequency of the νCN vibration, but potential energy calculations do not reveal the preferred angle for a nonlinear interaction.

The magnetization was measured in a single crystal sample of the orthorhombic ferroelectric paramagnetic β′-Tb2(MoO4)3 along the [0 0 1], [0 1 0] and [1 0 0] axes in the magnetic field up to 19 T at 4.2 K T K . An expression for the field and temperature dependence of the magnetization M(H,T) along the main directions was derived using the theory of the magnetism of singlets. Three lowest singlets of the spectrum of Tb3+ ion in β′-Tb2(MoO4)3 were taken into account. The existence of two types of sites for Tb3+ ions in β′-Tb2(MoO4)3 was taken into account. Magnetization curves were calculated by fitting this expression to the experimental curves. The results of the calculations agree with the experiment satisfactorily at low temperatures. As the results of fitting the saturation magnetic moments of Tb3+ ions at nonequivalent sites were found for three main directions. Their relative values reflect the symmetry of the nearest surrounding of Tb3+ ions.

Cesium-133 chemical shift and spin-lattice relaxation time measurements have been used to determine formation constants of the cesium ion complexes with 11 crown ethers, 15C5, 18C6, 21C7, DA18C6, DB18C6, DC18C6, DB21C7, DB24C8, DB27C9, DC21C7, and DC24C8, in formamide, N-methylformamide, dimethylormamide, and dimethylacetamide solutions. In the cases of 15C5, 18C6, DC21C7, and DC24C8, both LCs{sup +} and L{sub 2}Cs{sup +} complexes (L = crown ether) were observed; in all other systems only 1:1 complexes were formed. The formation of L{sub 2}Cs{sup +} complexes with DC21C7 and DC24C8 is surprising since both ligand cavities are larger than the cesium cation; previously, it was expected that only 1:1 complexes would form under such circumstances. In addition to the match between the cation diameter and ligand cavity, such factors as solvation of the complexation partners and the structure of the solvent itself affect the stability of the macrocycle-cation complexes. The selected amide solvents have similar donicities and dipole moments; in general, consistent with expectations for ion-dipole interactions, the calculated stability constants were larger in the lower dielectric constant media. 23 refs., 9 figs., 4 tabs.

The formation constants for the complexation of Cs/sup +/ in six solvents by three crown ethers, 18-crown-6, dibenzo-18-crown-6, and dicyclohexyl-18-crown-6, were studied at 25/sup 0/C by cesium-133 NMR techniques. The solvents used, in the approximate order of decreasing first complexation constant for all crown ethers, were pyridine, acetone, propylene carbonate, acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide. In all solvents, 18-crown-6 formed both 1:1 and 2:1 (ligand to metal) complexes with enough difference between the complexation constants that the second constant could be determined. The formation of 2:1 complexes by the other two crown ethers was also indicated in most solvents but the second complexation constant could only be measured for the dibenzo-18-crown-6 complex in pyridine. In many cases the first complexation constant was too large to measure by the NMR technique so that only lower bounds could be established. The rate of loss of the Cs/sup +/ ion from dicyclohexyl-18-crown-6 and from monobenzo-2,2,2-cryptand in propylene carbonate was measured as a function of temperature. The activation energy for the latter case (15 kcal mol/sup -1/) is substantially larger than for the crown ether complex (8.5 kcal mol/sup -1/). Although the chemical shifts of both Cs/sup +/ and its 1:1 complex with 18-crown-6more » are strongly solvent dependent, the chemical shift of the 2:1 complex is independent of solvent, indicating that in the ''sandwich'' complex the cesium ion is effectively shielded from the solvent.« less

Solvation of the lithium ion by acetone was studied in acetone-nitromethane solutions by Raman, infrared, and7Li and35Cl NMR spectroscopic techniques. It was confirmed that the 390-cm−1 IR acetone band is split by the lithium ion and that a 369-cm−1 IR band, attributed by other authors to Li+-nitromethane vibration, is due to the vibration of acetone in the lithium inner solvation shell. The frequency of the Li+-nitromethane vibrational band is strongly anion dependent due to contact-ion-pair formation. Several different techniques indicate that Li+ is solvated by four acetone molecules, and approximate equilibrium-constant values for the stepwise solvation reaction were calculated. The influence of weak complexing agents on Li+ ClO4− ion-pair formation was investigated.

Lithium-7 NMR studies have been carried out on lithium ion complexes with crown ethers 12C4, 15C5, and 18C6 in water and in several nonaqueous solvents. In all cases the exchange between the free and complexed lithium ion was fast on the NMR time scale, and a single, population average, resonance was observed. Both 1:1 and 2:1 (sandwich) complexes were observed between lithium ion and 12C4 in nitromethane solution. The stability of the complexes varied very significantly with the solvent. With the exception of pyridine, the stability varies inversely with the Gutmann donor number of the solvent. In general, the stability order of the complexes was found to be 15C5·Li+>12C4·Li+>18C6·Li+. Calorimetric studies on these complexes show that, in most cases, the complexes are both enthalpy and entropy stabilized.

Potassium-39 NMR study of K+ ion in molten KSCN and some molten salt mixtures show that the resonance frequency is highly dependent on the nature of the counterion and the technique can be used for...

The application of far- and mid-infra-red, Raman, alkali metal n.m.r. and 35Cl n.m.r. techniques to the study of electrolyte solutions in non-aqueous solvents is discussed. The above techniques are very sensitive probes of the environment of ions in solutions. They have been used to detect contact ion pair formation and to determine cationic solvation numbers. 23Na chemical shifts in different solvents, which are strongly influenced by the paramagnetic screening constant, show a linear relationship with Gutmann's donor numbers for these solvents.

The influence of the immediate chemical environment of Ca2+ ion on the 43Ca resonance was studied in aqueous and nonaqueous solutions by calcium-43 NMR.

Cesium-133 chemical shifts were measured in a number of solvents as a function of salt concentration and of the counterion. Infinite-dilution chemical shifts (vs. aqueous Cs+ ion at infinite dilution) ranged from +59.8 ppm for nitromethane solutions to −29.4 ppm for pyridine. In general, the magnitude of the downfield chemical shift reflected the donor ability of the solvents. Ion-pair formation constants were calculated from the concentration dependences of133Cs chemical shifts in several nonaqueous solvents.

In acetonitrile solutions, the exchange reaction is bimolecular in the Tl+ + 18C6 system, while in the Tl+ + pentaglyme system the associative-dissociative and the bimolecular mechanisms coexist at room temperature and the bimolecular exchange reaction dominates at 263° K. For the bimolecular mechanism in the case of Tl+ + 18C6 and the associative-dissociative mechanism in the case of Tl+ + pentaglyme, the activation energies of the exchange reactions change with temperature. At 298° K, in the Tl+ + 18C6 system the activation energy for the bimolecular exchange reaction is ≈ 2 kcal.mol−1 and exchange rate constant (k1) is (4.1 ± 0.1) × 107 s−1mol−1; in the Tl+ + pentaglyme system, the activation energy for the associative-dissociative exchange reaction is ≈ 5 kcal mol−1 and the decomplexation rate constant (k−2) is (2.2 ± 0.4) X 105 s−1. The activation energy for the bimolecular exchange in the Tl+ + pentaglyme system was determined to be 3.00 ± 0.05 kcal.mol−1 and the exchange rate constant (3.0...

Magnesium-25 NMR measurements were carried out on aqueous and non-aqueous solutions of magnesium salts. In the former case the25Mg resonance frequency was independent of the concentration or of the counterion. In nonaqueous solvents, however, the resonance frequency was dependent on the solvent, the concentration, and on the nature of the counterion, indicating some cation-anion interactions. Measurements on Mg2+—phosphonoacetic acid mixtures in aqueous solutions gave strong indications of complexation. Only inconclusive evidence was obtained on the complexation of Mg2+ by macro-bicyclic cryptand C211 in methanol solutions, and no evidence of complexation was obtained with macrocycle 12-crown-4 in dimethylformamide solutions.

Solutions of zinc salts in water, methanol (MeOH), dimethylformamide (DMF) and binary mixtures of water with the two nonaqueous solvents were studied by zinc-67 NMR measurements. Anhydrous zinc nitrate solutions in DMF and MeOH show upfield, concentration independent, chemical shifts at −27 and −19 ppm, respectively, vs. the aqueous solution standard. Addition of DMF or MeOH to an aqueous solution of a zinc salt results in a diamagnetic shift but for the addition of acetonitrile a paramagnetic shift results. In all cases the signal was broadened very considerably, e.g., in ZnCl2 solution the linewidth increased from ∼40 to ∼600 Hz in going from water to 35% aqueous MeOH. Both67Zn and13C NMR failed to show any complexation of Zn2+ ion by crown ethers in aqueous solution. A gradual addition of EDTA, of diaza-18-crown-6 or of tetraazacyclotetradecane resulted in an immediate broadening of the67Zn signal which became undetectable when one equivalent of a ligand was added.

Complexes of 1,10-diaza-18-crown-6 macrocycle with Tl+, Li+, Na+ and Cs+ ions were investigated by multinuclear NMR technique in a number of non-auqueous solvents. With the exception of pyridine solutions the stabilities of the complexes varied inversely with the Guttmann donicity of the solvents. In a given solvent, the complexity constants decreased in the order Ti+ > Li+ > Na+ > Cs+. A somewhat different order is observed for the analogous polyehter 18-crown-6, where it is, Tl+ > Cs+ > Na+ > Li+.

Fluorine-19 and sodium-23 NMR measurements were carried out on sodium hexafluorophosphate solutions in a number of solvents. In solvents of medium polarity and donicity (e.g., propylene carbonate, acetone, acetonitrile) the19F chemical shift moved upfield with increasing concentration of the salt. This behavior is indicative of anion-cation interactions which may be of long-range type, i.e., formation of solvent-separated ion pairs; the possibility of contact ion pair formation, however, cannot be excluded. In solvents of low polarity and donicity (acetic acid, tetrahydrofuran), the salt is essentially completely associated in the 0.1–1.0M concentration range. On the other hand, in solvating solvents with high dielectric constants, such as dimethyl-formamide, dimethylsulfoxide, and formamide, there is very little ionic association in the same concentration range. The above conclusions are supported by23Na chemical shift measurements. Potassium hexafluorophosphate solutions do not show any concentration dependence of the19F chemical shifts, while for tetra-n-butylammonium solutions the19F resonance moves downfield with increasing concentration of the salt.

Thermodynamic parameters for the complexation of the cesium ion by macrocyclic polyethers, dibenzo- 27-crown-9, (DB27C9), and dibenzo-24-crown- 8, (DB24C8), were determined in dimethylformamide— acetonitrile binary solvent systems by cesium- 133 NMR technique. Enthalpies and entropies of the complex formation were obtained from the temperature dependence of the complexity constant. In all cases the complexes are enthalpy stabilized but entropy destabilized and both parameters are quite sensitive to the solvent composition.

Determination des constantes de stabilite des complexes des metaux alcalins, Tl + et Ba 2+ dans acetonitrile, acetone et carbonate de propylene