Tartrate Solution Research Articles

Effects of organic acids on copper and cadmium desorption from contaminated soils

A study was conducted to investigate the effect of organic acids on Cd and Cu desorption from natural contaminated soils (NCS) with permanent contamination by metal smelters and from artificial contaminated soils (ACS) derived from an artificial amendment of Cd to three representative zonal soils in Central China. Results showed that the desorption of Cd in either NCS or ACS, with the increment of tartrate or citrate concentration in desorption solution, can be characterized as a valley-like curve. The presence of tartrate or citrate at a low concentration (≤0.5 mmol/l) inhibited Cd desorption from these two types of soils, whereas the presence of organic acids at high concentrations (≥2 mmol/l for citrate and about ≥15 mmol/l for tartrate) apparently promoted Cd desorption. The desorption curve of Cu by tartrate solution with different tartrate concentrations can also be characterized as a valley-like curve, while the desorption of Cu in the presence of citrate was directly enhanced with the increment of citrate concentration. With the enhancement of initial pH value from 2 to 8 in the presence of citrate, Cu desorption ratio decreased at the first stage, then increased, and then decreased again. A valley and a peak sequentially appeared in the Cd or Cu desorption curve with initial pH value increment. Compared with citrate, the desorption ratio of Cd or Cu from NCS or ACS was directly decreased in the presence of tartrate, with the enhancement of the pH value from 2 to 8. Cd or Cu desorption was clearly enhanced when the electrolyte concentration of KNO 3 or KCl increased in the presence of 2 mmol/l tartrate. Moreover, a higher desorption ratio of Cd or Cu was shown with KCl electrolyte than with KNO 3 electrolyte with the same concentration. Based on these observations, we suggest that bioavailabilities of heavy metal can be promoted with selected suitable types and concentrations of organic acid amendment and reasonable field condition.

Effect of citrate impurities on the reference pH value of potassium dihydrogen buffer solution

Solutions of potassium dihydrogen citrate, KH 2C 6H 5O 7, exhibit reference pH values close to those of the primary standard pH buffer solutions of tartrate and phthate. Nevertheless, as opposed to all other recommended primary buffer standards, the citrate reagent is not commercially available as a standard reference material (SRM). In this work, experiments have been performed on solid reagent from different sources, which revealed the presence of the various citrate species in variable amounts. This may arise from the sensitivity of the system to the purification strategy, owing to the proximity of the acidity constants of the triprotic citric acid, H 3C 6H 5O 7. An experimental procedure has been developed which leads to a satisfactory preparation of the citrate reagent, to an extent that its solutions, independently of batch on supplier, exhibit reproducible pH values, in agreement with the conventionally assigned pH (S) = 3.776 at 25 °C for 0.05 m KH 2C 6H 5O 7. Comparison of expected and experimental values is used as a quantitative test for the quality of reagent, eventually indicating the need for purification according to recommendations.

Precipitation of bismuth(III) tartrates from nitrate solutions

The precipitation of bismuth(III) from nitrate solutions on addition of aqueous solutions of tartaric acid and sodium tartrate was studied by X-ray phase analysis, thermogravimetry, IR spectroscopy, and chemical analysis. Conditions for the formation of [Bi(NO3)(H2O)3]C4H4O6 and [Bi(C4H4O6)(C4H5O6)] · 3H2O were determined.

Towards atomic resolution with crystals grown in gel: the case of thaumatin seen at room temperature.

One reason for introducing a gel in the crystallization medium of proteins is its ability to reduce convection in solution. This can lead to better nucleation and growth conditions, and to crystals having enhanced diffraction properties. We report here the X-ray characterization at room temperature of high-quality crystals of the intensely sweet thaumatin prepared in a sodium tartrate solution gelified with 0.15% (m/v) agarose. Using a synchrotron radiation, these crystals diffracted to a previously unachieved resolution. A diffraction dataset was collected from four crystals at a resolution of 1.2 A with a R(sym) of 3.6% and a completeness of 99%. Refinement was carried out to a final crystallographic R-factor of 12.0%. The quality of the electron density map allowed for the observation of fine structural details in the protein and its solvation shell. Crystallization in gel might be used more generally to improve the quality of macromolecular crystals. Advantages provided by the gelified medium in the frame of structural studies are emphasized.

Characterisation of the surface films formed on Nb during electrodissolution in aqueous alkali

Anodic polarisation of Nb in warm and concentrated aqueous alkali results in sustained electrodissolution. The process is investigated in NaOH by voltammetric, steady-state and impedance techniques. The j– E steady-state curve is characterised by a current peak and a subsequent plateau extending up to the explored positive limit (8 V SCE). Upon addition of tartrate to the electrolyte the dissolution current increases markedly. In some NaOH+Na tartrate electrolytes a dissolution–precipitation mechanism sets in, with formation of a surface layer which causes a gradual current decrease; this layer is identified by XRD and elemental analysis as a mixed Na and Nb oxide hydrate. Larger currents may be sustained in KOH+K tartrate solutions without any precipitation process. Impedance diagrams recorded in the plateau region are analysed on the basis of the equivalent circuit resulting from the surface charge model; the oxide formation ratio and the main model parameters are estimated and their temperature dependence is discussed.

Distribution of brimonidine into anterior and posterior tissues of monkey, rabbit, and rat eyes.

The objectives of the study were to evaluate the distribution of brimonidine (alpha2-adrenergic agonist) into anterior and posterior ocular tissues. Single or multiple doses of a 0.2 or 0.5% brimonidine tartrate solution were administered to one or both eyes of monkeys or to one eye of rabbits. Brimonidine was administered intraperitoneally to rats. After topical administration, [14C]brimonidine was rapidly absorbed into the cornea and conjunctiva and distributed throughout the eye. [14C]Radioactivity was higher and cleared more slowly in pigmented tissues (iris/ciliary body, choroid/retina, and optic nerve) than in nonpigmented tissues. Single and multiple dosing led to a similar drug distribution, with higher levels of brimonidine measured in pigmented tissues after multiple dosing. Most of the radioactivity extracted from ocular tissues represented unchanged brimonidine. In the rabbits and the monkey treated in only one eye, levels of radioactivity in the untreated eye were low, consistent with the low systemic levels and rapid drug clearance. Posterior ocular tissue concentrations of radioactivity exceeded systemic blood concentrations. The vitreous humor brimonidine concentrations in monkeys treated topically with 0.2% brimonidine tartrate was 82 +/- 45 nM. Vitreous levels in rabbits confirmed the penetration of brimonidine to the posterior segment. Similar concentrations of brimonidine (22 to 390 nM) were measured in the vitreous and retina of rats injected intraperitoneally with brimonidine. Both topically applied and systemically administered brimonidine reach the back of the eye at nanomolar concentrations sufficient to activate alpha2-adrenergic receptors. The brimonidine levels achieved at the retina are relevant for neuroprotection models.

Volumetric properties of aqueous solutions of disodium tartrate and dipotassium[formula omitted]-tartrate at temperatures from 278.15 K to 343.15 K and molalities (0.1, 0.5, and 1.0) mol·kg − 1

Densities of aqueous solutions of disodium tartrate at the molalities (0.09996, 0.49097, and 0.9649)mol · kg−1and of dipotassiuml-tartrate at the molalities (0.09993, 0.49769, and 0.9912)mol · kg−1were determined at 1 K temperature intervals from T= 278.15 K to T= 343.15 K. The densities were used to determine the apparent molar volumes, cubic expansion coefficients, the apparent molar expansibilities, and the second derivatives of the volume with respect to temperature which are related to the derivatives of isobaric heat capacities with respect to pressure.

Anodization of Al–Nd alloy films in nonaqueous electrolyte solutions for TFT-LCD application

The anodization behavior of Al–Nd alloys in nonaqueous electrolyte solutions and the electronic properties of the resultant anodic oxide films were studied for TFT-LCD application. Sputtered Al–Nd alloy films on glass substrates were anodized at 25 °C and 1 mA cm −2 up to 100 V in ethylene glycol–water solutions containing 10 wt.% ammonium tartrate or salicylate to give uniform and flat oxide films. The incorporation of organic components into the anodic oxide films from the electrolyte solutions has lowered the relative permittivity and increased the breakdown electric field of the oxide films. This was performed by decreasing the water content in the electrolyte solutions. The tartrate solution caused higher carbon incorporation than the salicylate counterpart at the same water concentrations, giving lower relative permittivity, and higher forward breakdown electric field. The AlO stretching frequency of the oxide films decreased slightly as the amount of incorporated organic moieties increased. Nd was uniformly distributed in the oxide films and an increase in the Nd content was likely to increase both the relative permittivity and the forward breakdown electric field without any apparent change in the anodization behavior.

Effect of silicon alloying addition on the corrosion behaviour of aluminium in some aqueous media

The corrosion behaviour of three Al–Si alloys was studied after galvanostatic passivation in 0.1 M sodium tartrate, sulfate and borate solutions using EIS techniques. The degree of passivation depends on the anion type, the degree of polarization and the alloy composition. It was also found that increase in pH led to a decrease in polarization resistance Rp. The effect of formation voltage, Vf, on the growth and dissolution kinetics of the oxide grown on the alloys was studied. The polarization resistance value increases as Vf increases up to a certain value; above this the Rp value decreases. This critical Vf depends on the alloy composition and the test solution. The kinetics of oxide layer dissolution in the absence and presence of Cl− ions was also studied. Increase in immersion time leads to a more severe attack by Cl− ions as shown by the decrease in the value of Rp. At low Cl− ion concentration the value of Rp is higher than that in chloride ion free sulfate solutions, because the rate of passive film repair is much higher than that of barrier layer dissolution. However, at high Cl− ion concentration penetration of Cl− through defects in the barrier layer leads to formation of an oxyhalide layer.

Changes of the Cu electrode real surface area during the process of electroless copper plating

The surface area (nanoscale roughness) of copper coatings deposited from electroless plating solutions containing Quadrol, L(+)- and DL(∓)-tartrate as Cu(II) ion ligands was measured using underpotential deposition thallium monolayer formation. Surface roughness of Cu coatings depends on the plating solution pH and the Cu(II) ligand, and varies over a wide range. In L(+)-tartrate and Quadrol solutions (pH 12.5–13.3) the roughness factor R f is low and is equal to 2–3 and 4–6, respectively (substrate: electrodeposited Cu; R f=2.2). Cu coatings of higher surface area are obtained in DL(∓)-tartrate (pH 12.3–12.7) and Quadrol (pH 12.0) solutions: R f reaches 20–30. The correlation between R f and Cu deposition rate was found in L(+)-tartrate solution. The Cu surface area changes are discussed in terms of partial electrochemical reactions of the autocatalytic Cu deposition process, and the decisive role of cathodic Cu(II) reduction from adsorbed Cu(II) complex species.

Determination of transition metals in human hair by high-performance liquid chromatography using sodium hexadecane-sulfonate coated columns

A chromatographic method for the determination of transition metals in human hair samples is described. The method involves the separation of Cu, Pb, Zn, Ni, Co, Cd and Mn in a C18 column coated with sodium hexadecane-sulfonate (SHS) and spectrophotometric detection (520 nm) after post-column reaction of the eluted metals with 4-(2-pyridylazo)-resorcinol (PAR). The eluent was a 100 mM tartrate solution adjusted to pH 3.1 with a 2 M sodium hydroxide solution (flow-rate=1.0 ml min −1). A good separation of the eluted metals (specially for Cu/Pb and Zn/Ni) has been achieved. The detection limits, expressed as μg l −1, were 2.2 (Cu), 8.0 (Pb), 2.8 (Zn), 1.5 (Ni), 1.5 (Co), 12.0 (Cd), and 1.4 (Mn). A microwave-assisted closed vessel acid digestion procedure with HNO 3+HClO 4 (4+1 ml) was used for the hair samples solubilisation. Nineteen hair samples were analysed with the proposed method. The results were in good agreement with those obtained by atomic absorption spectrometry (AAS).

Speciation of antimony(III) and antimony(V) species by using high-performance liquid chromatography coupled to hydride generation atomic absorption spectrometry

A miniaturized HPLC column (Supelcosil LC-SAX 1, 2 cm×4.6 mm id) was coupled to HGAAS for the speciation of inorganic SbIII and SbV species in spiked water samples. The baseline separation of these two Sb species was achieved by using aqueous 50 mmol l–1 tartrate solution at pH 5.5 as eluent. The retention times were 0.5 and 2.8 min for SbV and SbIII, respectively. The hydrides were generated with 3% NaBH4 and 1.8 mol l–1 HCl solutions. The absorbance was linearly related to the concentration of SbV species in the range 2.5–100 µg l–1 (r=0.9996) and of SbIII species in the range 5.0–100 µg l–1 (r=0.9990) with detection limits of 1.0 and 2.0 µg l–1, for SbV and SbIII, respectively. The precision, evaluated by using the relative standard deviation (RSD), was 3.3% and 1.5% (n=10) for SbV and SbIII at concentrations of 50 µg l–1, and 4.1% and 3.9% (n=10) at concentrations of 10 µg l–1, respectively. The detection limits achieved in the present work are acceptable for screening samples with respect to the EU drinking and surface water limits (10 µg l–1), but are not sufficiently sensitive to measure real levels in natural waters. The accuracy of the method was evaluated by the analysis of Sb species in several spiked water samples, as there is yet no certified reference material available.

Conductivity Studies on Aqueous Solutions of Stereoisomers of Tartaric Acids and Tartrates. Part III. Acidic Tartrates

Conductivity measurements on aqueous solutions of sodium hydrogen tartrate and potassium hydrogen tartrate were performed in the temperature range 5–35°C. By including the dissociation equilibria, the experimental conductivities of the acidic salts can be well described using equivalent limiting conductivities of the bitartrate anion λ∞(HTar−) and the tartrate anion λ∞ (1/2 Tar2−) when applying the Quint and Viallard equations for unsymmetrical electrolytes.

High-performance liquid chromatographic determination of trace amounts of transition metals in parenteral solutions

A high-performance liquid chromatographic (HPLC) method for the determination of trace levels of transition metals (Cu, Pb, Zn, Ni, Co, Cd and Mn) in parenteral solutions (large volume parenterals) was developed. The method involves a preconcentration step on a cation-chelating column (a Nova-Pak C18 guard column coated with Chrome Azurol S) and the separation of the different metals on a Nova-Pak C18 column permanently coated with sodium hexadecanesulfonate. The eluent was a 100 mmol l–1 tartrate solution of pH 3.1. Colorimetric detection (at 520 nm) after post-column reaction of the metals with 4-(2-pyridylazo)resorcinol was used. The conditions for the preconcentration and separation of the metals (composition, concentration and pH of the eluent) were studied. The repeatability of the results (n = 3) for a concentration level of about 50 µg l–1 was between 3.5% (Cd) and 5.5% (Ni). The limits of quantification for a preconcentrated sample volume of 4 ml, expressed as µg l–1, were 0.40 (Cu), 2.1 (Pb), 0.50 (Zn), 0.33 (Ni), 0.23 (Co), 2.5 (Cd) and 2.6 (Mn). The results obtained with the developed HPLC method for ten commercial samples and seven spiked pooled samples were evaluated by comparison with those provided by electrothermal atomic absorption spectrometry (ETAAS). The developed procedure might be a rapid and inexpensive alternative to ETAAS for quality control in the pharmaceutical industry.

Serendipity in Scientific Discovery: A Closer Look

SERENDIPITY IN SCIENTIFIC DISCOVERY: A CLOSER LOOK HOWARD GEST* The word serendipity was coined in 1754 by Horace Walpole, in a letter to one of his correspondents: I once read a silly fairy tale, called "The Princes of Serendip" [an ancient name for Sri Lanka] ; and as their Highnesses travelled, they were always making discoveries, by accidents and sagacity, of things they were not in quest of: for instance, one of them discovered that a mule blind of the right eye had travelled the same road lately, because the grass was eaten only on the left side, where it was worse than on the right—now do you understand Serendipity? [I]. In an interesting essay on creativity and scientific discovery, Luis Leloir, the 1970 Nobel Laureate in Chemistry, discussed serendipity and noted that The faculty ofmaking happy chance finds requires also careful and wise observation ... A trained research worker would surely find the evidence ver)' weak and the behavior of the mule rather odd. He surely would recommend confirmatory work such as observing the eating habits of a mule that has one eye covered. [2] Discussions of serendipity in scientific research tend to overemphasize "accident" as the prime factor, but the path from accidental observation to a significant discovery is usually forged by curiosity and hard work. Frequently overlooked in Walpole's original definition is the requirement for sagacity, the ability to see what is relevant and significant, or keen judgement . Numerous noteworthy researches in biological science were "directed ," in a sense, by serendipic observations, but it is often not easy to identify a single serendipic event as the crucial happening. This is illustrated in the following by several case histories. *Department of Biology, Indiana University, Bloomington, IN 47405.© 1997 by The University of Chicago. All rights reserved. 0031-5982/97/4101-1044$01.00 Perspectives in Biology and Medicine, 41, 1 ¦ Autumn 1997 21 Pasteur: "Chance Favors Only the Prepared Mind" Pasteur's brilliant career included many episodes in which serendipity led to important discoveries. The ' 'accidents" occurred so often that in his biography of Pasteur, Dubos lists a number of index entries under "Pasteur's luck" [3] . Two examples illustrate Pasteur's propensity for serendipic luck. During the course of his research on optical activity of organic compounds, Pasteur noticed that a tartrate solution had become turbid due to mold growth during warm weather. He found that D-tartrate was readily destroyed by the "mold fermentation," whereas the L-form was unaltered: The solution of paratartrate, at first optically inactive, soon becomes perceptibly levorotatory, and the rotation gradually increases and attains a maximum. The fermentation then stops. There is now no trace of the dextro tartaric acid left in the liquid, which on being evaporated and treated with an equal volume of alcohol yields a fine crop of crystals of ammonium levo tartrate. It was an accident which gave the clue to the solution of the problem [i.e., vaccination ]. Pasteur had begun experiments on chicken cholera in the spring of 1879, but a trivial difficulty came to interrupt the work after the summer vacation; the cultures of chicken cholera bacillus that had been kept in the laboratory during the summer failed to produce disease when inoculated into chickens. A new, virulent culture obtained from a natural outbreak was inoculated into new animals, and also into the chickens which had resisted the old cultures. The new animals, just brought from the market, succumbed to the infection in the customary length of time, thus showing that the culture was very active. But to the surprise of e.11, and of Pasteur himself, almost all the other chickens survived the infection . . . Pasteur immediately recognized in this accidental occurrence an analog)' with cowpox vaccination . [3] No wonder that Pasteur frequently said: "In the field ofexperimentation, chance favors only the prepared mind." Pasteur was a great exemplar of capitalizing on serendipity in research. He was able to exploit an accidental observation with intuition, sagacity, and persistence. Albert Szent-Gyorgyi and Vitamin C The Hungarian biochemist Albert Szent-Gyorgyi made a number of important pioneering discoveries on the mechanisms of biological oxidations and muscle biochemistry. He is also widely known as the discoverer...

Conductivity studies on aqueous solutions of stereoisomers of tartaric acids and tartrates. Part I. Alkali metal and ammonium tartrates

Conductivity measurements on aqueous solutions of disodium tartrate, dipotassium tartrate, sodium potassium tartrate, and diammonium tartrate were performed in the temperature range 5 to 35°C. The equivalent limiting conductivity of tartrate anion, λ∞(l/2 Tar2-) is evaluated.

Extraction of Zinc with Long-Chain β-Diketones and 4-Acyl-5-pyrazolones

Abstract The extraction of zinc with long-chain 4-acyl-5-pyrazolones and β-diketones was studied. For comparison with the commercial extractant LIX 54, the extraction parameters were studied for their dependence on pH and on the influence of ammonia and tartrate. Among the examined compounds, 1-phenyl-3-methyl-4-(2-ethylhexanoyl)-5-pyrazolone shows the best extraction results. Zinc as well as nickel and cadmium can be extracted from tartrate solution. The separation of zinc and cadmium is possible. The extraction is disturbed by the presence of complexing agents such as ammonia or cyanide.

Measurement of brimonidine concentrations in human plasma by a highly sensitive gas chromatography/mass spectrometric assay

Brimonidine is an α 2-adrenergic agonist that is efficacious in lowering intraocular pressure in humans. A highly sensitive and selective gas chromatography/mass spectrometry (GC/MS) assay is described for quantitation of brimonidine in human plasma following ocular installation. Brimonidine in 1 ml of plasma was extracted together with tetradeuterated brimonidine (internal standard) and clonidine (carrier) by solvent extraction. After solvent evaporation, 3,5-bis(trifluoromethyl)benzoyl derivatives were formed and injected onto a GC/MS appartus under negative chemical ionization conditions. The ions monitored for derivatized brimonidine and tetradeuterated brimonidine were m/ z 691 [M - HBr] and m/ z 694 [M - DBr], respectively. Calibration curves were linear from 2 to 1000 pg ml −1 ( r 2 = 0.981-0.996). The method was specific for brimonidine relative to endogenous compounds in plasma. The inter-day relative standard deviation for analysis of quality controls was 12% or less, and the inter-day assay accuracy ranged from 97 to 104% of nominals. The GC/MS assay showed adequate sensitivity for analysis of human samples from volunteers ocularly dosed with 0.5% brimonidine tartrate solution. Overall, the GC/MS assay showed excellent precision and accuracy, and a minimum quantifiable concentration of 2 pg ml −1.

Reaction Condition for the Synthesis of Ultrafine Particles of the High‐Vacancy‐Content Zn(II)‐ Bearing Ferrites from Iron(III) Tartrate Solution

Reaction conditions for the synthesis of ultraflne particles of ferrite solid Solutions between ZnFe2O4 and γ‐Fe2O3 rep‐resented by x(ZnFe2O4)‐ y(Fe3O4)‐ z(γ‐Fe2O3), where x + y + z = 1 (0.09 x 0.73, y 0.08,0.22 z 0.88) (high‐vacancy‐content Zn(II)‐ bearing ferrites), were studied using the strongly alkaline Solutions of Fe(III) tartrate con‐taining Zn(II) ions at 100°C. The crystal growth of the ferrite particles was enhanced with the Zn(II) ions in the reaction solution. The number of nuclei of the ferrite was dependent on the Fe(III) or the tartrate concentration, which influenced the ultraflne particle size of the ferrite. The average particle size of the high‐vacancy‐content Zn(II)‐ bearing ferrites ranged from 7 to 38 nm. The room‐temperature Mössbauer effect of the high‐vacancy‐content Zn(II)‐ bearing ferrite (x = 0.34–0.37, y 0.02, z = 0.62–0.65) revealed the superparamagnetic nature for ultrafine particle sizes less than 20 nm. The ferrite was transferred from superparamagnetic to ferrimagnetic with an increase in the particle size (>20 nm) at room temperature.

Properties of powders of the system Sn(IV)-Sb-O and the resistivity of resistive thick films based on them

Tin dioxide powder doped with oxides of antimony are widely used as the conducting phase of high-resistance thickf i l l resistors made of composites [1]. The dispersity and structural-morphological properties of such powders determined by the method of production have a direct effect on formation of the microstructure and the mechanism of electrical conduction in the f i l l . The literature [2, p. 78] contains information only on the manner in which the resistance of such resistors is affected by the form of particles of doped tin dioxide produced by two laboratory methods. We made a study of the chemical, phase, and grannlometric composition, dispersity, and shape of particles of the system S n ( I V ) S b O obtained by four commercial methods. We also studied certain electrical properties of resistive films obtained from these particles. We used powders prepared by the following method: calcining together with hydrates of tin(IV) oxide and antimony(III) oxide precipitated from solutions of their chlorides (TU 06709-87) powder 1; calcining of powders obtained by drying (during atomization) of aqueous solutions of tin oxalate and antimony tartrate (TU 6-09-27-127-86) powder 2; calcining of products obtained by the heterogeneous oxidation of tin(II) sulfate and antimony(III) oxide by hydrogen peroxide (TU 6-09-27-127-86) powder 3; homogeneous oxidation of tin(II) sulfate and antimony(V) chloride by hydrogen peroxide (TU PG 430.411.02) powder 4. The materials were chemically analyzed by the method described in [3], which allowed us to establish the content of Sb(III) and Sb(V) ions. An x-ray diffraction analysis was performed on a DRON-0.5 diffractometer; the composition of the vapor was determined with an MI-1305 mass spectrometer. The granulometric composition of the powders was studied using an "SK Laser Micron Size PRO-7000" laser analyzer, while specific surface was determined by the method of mercury porometry. The density of the powdered materials was determined on an "Auto True Denser MAT-5000," and particle shape and size were evaluated with a "Cambridge Stereoscan $4-10" scanning electron microscope. The latter was also used to study the microstructure of longitudinal and transverse sections of resistive thick films. Thick-film elements were made by a standard technology metal-screen printing of patterns on a ceramic substrate from material VK 94-1, followed by heat treatment in air in a Pt~K-8 electric conveyor furnace. Film thickness was 25-30 /zm. The paste used in the printing process includes powders of the conducting phase, glass of grade S 279-2 [4], and an organic binder. The binder was burned off during firing of the films. In our study, the contact areas were made using a silver-palladium paste that had been pressed onto the substrate beforehand. The specimens had the form of squares with dimensions of 2 × 2 mm. The resistance of the films was measured at room temperature, while the temperature coefficient of resistance (TCR) was determined within the range 293-443 K by means of an Shch302 digital ohmmeter. It is known [5, 6] that Sn 1 _xSbxO2 solid solutions are formed in the system Sn(IV) S b O , the composition of these solutions being determined by the temperature and duration of the production process. Two-stage synthesis at 873 and 1270 K and holding for 16 and and 14 days, respectively, produces stable equilibrium phases with x _< 0.12 (9.7%).* There is as yet no consensus on the valence of the antimony in these phases. A reduction in temperature leads to the formation of solid solutions with a high concentration of antimony. Studies have shown that thick-film resistors formed with conducting-phase powders obtained at 1270-1320 K over a treatment time of 2-4 h have the optimum electrical properties. There is no advantage to a longer heat treatment. Thus, all commercial powders are produced under these condkions, regardless of the synthesis method employed. We can therefore