Effects of temperature and moisture on the anaerobic digestion of refuse

The influence of the first-tier variable temperature on the anaerobic decomposition of refuse was investigated by use of laboratory models. Temperature was found to exert significant effects on the interrelated metabolic processes of acidogenesis, solventogenesis and methanogenesis. A temperature elevation from a mean ambient regime (18.7°C) to 30°C resulted in a 2.6-fold increase in the methanogenic rate while a 7.8-fold increase was observed when the temperature was raised from 18.7 to 40°C. The rate of methanogenesis at 40°C was approximately three-fold higher than at 30°C. Further temperature elevation to 55°C, however, resulted in the cessation of methanogenesis although solventogenesis was promoted. An attempt was made to extrapolate the results obtained to actual landfill, with specific reference to the role of refuse density in thermogenesis.     

Impacts of temperature on the leaching of organotin compounds from poly(vinyl chloride) plastics—A study conducted under simulated landfill conditions

The aim of the study was to investigate whether organotin‐stabilized poly(vinyl chloride) (PVC) products could contribute to the pool of organotins observed in landfill leachates, and if the possible release could be related to different temperatures and landfill degradation phases. Small‐scale anaerobic reactors filled with generic household waste, a mixture of inocula, and different PVC plastics were used in the study and incubated at 20, 37, 55, and 70°C. The reactor units incubated at temperatures of 20–55°C underwent the anaerobic degradation phases that are characteristic for the aging of landfilled waste material. There were, however, differences in the duration of the phases as well as in the total biogas production among the units. Under methanogenic conditions greater losses of organotin compounds were observed as compared to acidogenic conditions. It was shown that the release of organotin stabilizers increases considerably at temperatures above the glass transition of the PVC products. A dealkylation from di‐ into monoalkyltin species was observed, as well as a possible methylation of inorganic tin. However, the main part of the organotins was adsorbed into the solid waste matrix. J. VINYL ADDIT. TECHNOL., 13:176–188, 2007. © 2007 Society of Plastics Engineers     

Effects of Storage Temperature and Water Activity on the Degradation of Carotenoids Contained in Microencapsulated Chili Extract

The aim of this work was to evaluate the effects of storage temperature and water activity on degradation of carotenoids contained in microencapsulates of non-aqueous extracts from chili (NAEC). Total carotenoids content and adsorption isotherms of microencapsulated NAEC in a 1:1 weight ratio with gum Arabic-maltodextrin DE 20 (GA 50%–MD50%) were determined at 25, 35, and 40°C. The isotherms were fitted using the Guggenheim-Anderson-de-Boer model and their enthalpies and entropies, both differential and integral, were estimated by the Clausius-Clapeyron method. The minimum integral entropy was considered as the point of maximum stability at which water less readily participates in degradation reactions. Zones of minimum integral entropy were found between 7.56–8.30, 6.10–6.95, and 5.15–6.04 kg H₂O/100 kg dried solids, corresponding to water activity (a_w) of 0.210–0.239, 0.238–0.277, and 0.262–0.313 at 25, 35, and 40°C, respectively. Total carotenoids content (CT) degraded over time, but degradation of carotenoids was lower in microcapsules stored at 25°C than those stored at 35 or 40°C. The morphology of microcapsules was altered at a_w > 0.6, including swelling of the polysaccharide matrix was presented, and possible subsequent dissolution of the wall material, which indicates a high rate of carotenoid degradation. When microencapsulated NAEC were storage between 0.2–0.6 of water activity, the highest glass transition temperatures were achieved. In this range, the wall materials of the microcapsules suffer less microstructural modifications, associated with the minimum level of degradation of carotenoids. Sometimes, in this water activity range, the zones of minimal entropy were observed.     

The influence of calcination temperature on catalytic activities in a Co based catalyst for CO2 dry reforming

The carbon dioxide dry reforming of methane (CDR) reaction could be thermodynamically favored in the range of 800 to 1,000 °C. However, the catalyst in this reaction should be avoided at the calcination temperature over 800 °C since strong metal support interaction (SMSI) in this temperature range can decrease activity due to loss of active sites. Therefore, we focused on optimizing the temperature of pretreatment and a comparison of surface characterization results for CDR. Results related to metal sintering over support, re-dispersion by changing of particle size of metal-support, and strong metal support interaction were observed and confirmed in this work. In our conclusion, optimum calcination temperature for a preparation of catalyst was proposed that 400 °C showed a higher and more stable catalytic activity without changing of support characteristics.     

Stability and Stabilization of Enzymes from Mesophilic and Thermophilic Organisms in Respect to Their Use in FIA-Systems for the Determination of L-Lactate and Acetate

The stabilization effect of ‘bilayer encagement’ on enzymes from mesophilic organisms and their ‘thermophilic’ counterparts was compared. Lactate dehydrogenases from pig heart and from a thermophilic bacterium (Clostridium thermohydrosulfuricum), respectively, showed stabilization factors of 4·5 (at 47°C) and 12·8 (at 70°C), respectively. For ‘thermophilic’ acetate kinase no stabilization effect of encagement was observed. Lactate dehydrogenase and acetate kinase from Clostridium thermohydrosulfuricum were immobilized to controlled porous glass and tested for their long-term stability. The ‘thermophilic’ enzymes showed by far a longer half-life as compared with the corresponding enzymes from pig heart and Escherichia coli, respectively, the half-life time of the flow injection system response with thermophilic lactate dehydrogenase at 35°C attaining 250 h (mesophilic enzyme 89 h), and with thermophilic acetate kinase 79 h (mesophilic enzyme 24 h). © 1997 SCI.     

Effects of composition and temperature on extrudate characteristics,morphology, and tensile properties of acrylic rubber–blended PVC

Poly(vinyl chloride) was blended with acrylic rubber over a range of compositions (5–40 wt % of the rubber), using a twin‐screw extruder. Morphological properties of the blends were investigated as a function of rubber content and blending temperature, using a scanning electron microscopy. The mechanical properties of the blends were determined by a tensile test. Smooth extrudates were obtained at the blending temperature of 155°C. At a higher blending temperature (195°C), greater die swell ratio and/or melt‐fractured extrudates were observed, depending on the rubber content. Miscible blends were obtained at low rubber contents (5–10 wt %). A dispersed particle morphology was observed from the extrudates containing the rubber content of 20–40 wt %, at 195°C. The ultimate tensile stress (UTS) and modulus of the blends decreased with the rubber content. The maximum tensile toughness was obtained for the blend with a rubber content of 20%, at a blending temperature of 155°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2523–2534, 2001     

The effect of exchanged cations and heat treatment on the adsorption of carbon monoxide,nitrogen, argon,and krypton on amorphous silica-alumina cracking catalysts

Adsorption isotherms for CO, N₂, Ar, and Kr were measured over the temperature range ?50–250 °C over a pressure range of 2–350 Torr on exchanged and unexchanged silica-alumina cracking catalysts that had been evacuated at 250, 450, and 800 °C, respectively. Isosteric heats of adsorption were calculated at surface coverages ranging from 0.1 to 1%.When the samples were evacuated at 250 °C, the adsorption of CO was increased by a factor of about 3.5 when the exchanged cations were Ca and Ba and about 50% for K cations and also for ions of La and Mg. The influence of cations became even greater when the samples were evacuated at 450 °C, the adsorption for the samples exchanged with cations being three times as great on specimens evacuated at 450 °C as for samples evacuated at 250 °C. Evacuation of samples at 800 °C caused the adsorption of CO on the H form of the sample to be substantially the same as for the ones exchanged with calcium ions. The isotherm for the Ca exchanged specimen was substantially the same as for the sample evacuated at 450 °C.Isosteric heats of adsorption in general were highest for La and Ca exchanged samples, somewhat lower for those exchanged with K and least for those containing protons on the exchange sites. However the heats of adsorption on samples evacuated at 800 °C approached 15 kcal/mole of CO both for samples exchanged with Ca ions and for the protonic samples. Corresponding heats of adsorption of nitrogen were in the range of 7–9 kcal/mole of N₂. Heats of adsorption of argon and krypton remained down in the range of 2.5–3.5 kcal/mole for all samples, and were not much influenced by the temperature of evacuation or the exchange of ions on the catalyst surface. The molecules for which the big changes in adsorption with temperature of evacuation and ion exchange of samples were noted were carbon monoxide and nitrogen, both of which have rather high quadrupole moments.     

High-dose,intermediate-temperature neutron irradiation effects on silicon carbide composites with varied fiber/matrix interfaces

SiC/SiC composites are promising structural candidate materials for various nuclear applications over the wide temperature range of 300–1000 °C. Accordingly, irradiation tolerance over this wide temperature range needs to be understood to ensure the performance of these composites. In this study, neutron irradiation effects on dimensional stability and mechanical properties to high doses (11–44 dpa) at intermediate irradiation temperatures (?600 °C) were evaluated for Hi-Nicalon Type-S or Tyranno-SA3 fiber–reinforced SiC matrix composites produced by chemical vapor infiltration. The influence of various fiber/matrix interfaces, such as a 50–120 nm thick pyrolytic carbon (PyC) monolayer interphase and 70–130 nm thick PyC with a subsequent PyC (?20 nm)/SiC (?100 nm) multilayer, was evaluated and compared with the previous results for a thin-layer PyC (?20 nm)/SiC (?100 nm) multilayer interphase. Four-point flexural tests were conducted to evaluate post-irradiation strength, and SEM and TEM were used to investigate microstructure. Regardless of the fiber type, monolayer composites showed considerable reduction of flexural properties after irradiation to 11–12 dpa at 450–500 °C; and neither type showed the deterioration identified at the same dose level at higher temperatures (>750 °C) in a previous study. After further irradiation to 44 dpa at 590–640 °C, the degradation was enhanced compared with conventional multilayer composites with a PyC thickness of ?20 nm. Multilayer composites have shown comparatively good strength retention for irradiation to ?40 dpa, with moderate mechanical property degradation beginning at 70–100 dpa. Irradiation-induced debonding at the F/M interface was found to be the major cause of deterioration of various composites.     

Thermooxidative degradation behavior of poly(silphenylene–siloxane)s

Copolymers of poly(silphenylene–siloxane) with dimethylsiloxane and diphenylsiloxane with various end groups were synthesized through an Si? H/Si? OR polycondensation process. The thermooxidative degradation behaviors of the copolymers were investigated by thermogravimetric analysis and IR spectrometry techniques. All of the polymers were characterized by a two‐step mass loss. The first one, which peaked at 510–545°C in differential thermogravimetric curves, was mostly caused by the main‐chain depolymerization, whereas the second one, which reached its maximum around 650°C, was caused by side‐group oxidation and Si? C bond scission. The main‐chain depolymerization occurred over a temperature range of some 470–580°C, whereas Si? C bond scission and side‐group oxidation occurred over a temperature range of about 585°C to above 720°C. The incorporation of phenyl groups in the end groups greatly retarded the temperature for the degradation onset of the main chain to 120°C higher. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Phase equilibrium in binary La2O3-Dy2O3 and ternary CeO2-La2O3-Dy2O3 systems

Cerium oxide doped with oxides of rare earth elements is a multifunctional material, a wide range of uses which is associated with its unique physicochemical properties. Phase diagrams of multicomponent systems are the physicochemical basis for the creation of new materials with improved characteristics.In this work, phase equilibria in ternary CeO₂–La₂O₃–Dy₂O₃ and binary La₂O₃–Dy₂O₃ systems in the whole concentration range were studied. No new phases have been identified in these systems. An isothermal section of the phase diagram of the CeO₂–La₂O₃–Dy₂O₃ system at a temperature of 1500 °С is constructed. No new phases have been detected in the system. It was found that in the studied ternary system solid solutions are formed on the basis of (F) modification of CeO₂ with structure of fluorite type, monoclinic (B), cubic (C) and hexagonal (A) modifications of Ln₂O₃.In the La₂O₃–Dy₂O₃ binary system (1500–1100 °С) three types of solid solutions are formed: based on hexagonal modification A-La₂O₃, monoclinic modification B-Dy₂O₃ and cubic modification C-Dy₂O₃ separated by two-phase fields (A+B) and (B+C), respectively. The boundaries of the regions of homogeneity of solid solutions based on A-La₂O₃ are determined by compositions containing 35–40, 20–25, 15–20 mol% Dy₂O₃ at 1500, 1250, 1100 °C, respectively. From the obtained data it follows that the solubility of Dy₂O₃ in the hexagonal modification of lanthanum oxide is 39 mol% at 1500 °C, 23 mol. % at 1250 °C and 16 mol% at 1100 °C. The limits of existence of solid solutions based on monoclinic B-modification are determined by compositions containing 30–35, 65–60 (1250 °С), 35–40, 55–60 (1100 °С) 40–45, 70–75 (1500 °C) mol% Dy₂O₃.In the studied system, with a decrease in temperature from 1500° to 1100°C, there is a decrease in the solubility of La₂O₃ in the crystal lattice of cubic solid solutions of C-type from 16 to 10 mol%.     

The dielectric behavior of natural resin shellac

The Cole-Cole method has been applied for an analysis of the dielectric relaxation data of the natural resin shellac, obtained by Bhattacharya in the temperature range 20–110°C. Three relaxation processes were observed for temperatures 20–60°C. At 70°C, two relaxation processes were noticed, whereas only one was observed by Bhattacharya between 20 and 110°C. The relaxations at 80°C and above represented typical Cole-Cole type. The variation of the static dielectric constant with temperature revealed three distinct slopes, which indicated different phases of the resin during its thermal transition from solid to liquid state. Two “transformation points,” around 40 and 70°C were noted, i.e., the glass transition temperature and melting point of the resin, respectively. Significant changes in static dielectric constant, dielectric increment, relaxation time, and Cole-Cole distribution parameter were observed during a rise of temperature from 80 to 110°C. The results of the present study indicate that some rearrangement in the teriary disposition of the resin molecules takes place during the rise of temperature from 20 to 110°C.     

High-Rate Anaerobic Treatment of Malting Waste Water in a Pilot-Scale EGSB System Under Psychrophilic Conditions

The feasibility of the expanded granular sludge bed (EGSB) system for the treatment of malting waste water under psychrophilic conditions was investigated by operating a pilot-scale 225·5 dm³ EGSB-reactor system in the temperature range from 13 to 20°C. The concentration of chemical oxygen demand (COD) in the malting waste water was between 282 and 1436 mg dm⁻³. The anaerobically biodegradable COD of the waste water was about 73%, as determined in the batch bioassays. During reactor operation at 16°C, the COD removal efficiencies averaged about 56%, at organic loading rates (OLR) ranging between 4·4 and 8·8 kg COD m⁻³ day⁻¹ and a hydraulic retention time (HRT) of approximately 2·4 h. At 20°C, removal efficiencies were approximately 66% and 72%, respectively, at OLRs of 8·8 and 14·6 kg COD m⁻³ day⁻¹, corresponding to HRTs of 2·4 and 1·5 h. The specific methanogenic activity with the sludge from the reactor, assessed on acetate and volatile fatty acids mixture as substrates, significantly increased (80%) in time, indicating an enrichment of methanogens and acetogens even at the low temperatures applied. These findings are of considerable practical importance because they indicate that anaerobic treatment of low strength waste waters at low temperature might become a feasible option. © 1997 SCI.     

Synthesis of acrolein by gas‐phase dehydration of glycerol over silica supported Bronsted acidic ionic liquid catalysts

BACKGROUND: Glycerol has become readily available as a byproduct from the biodiesel industry. High functionality and relatively low price make it a potential building block to produce value‐added derivatives such as acrolein. RESULTS: Dehydration of glycerol to acrolein was performed over several silica supported Brønsted acidic ionic liquids as catalysts. All the catalysts prepared were active for the synthesis of acrolein (conversion of glycerol was observed in the range 35–90% with selectivity to acrolein in the range 29–58%). CONCLUSIONS: Catalyst prepared from triphenyl (3‐sulfopropyl) phosphonium 4‐methylbenzenesulfonate gave good activity and selectivity at 4 h reaction time. The conversion of glycerol decreased with increase in glycerol concentration. Higher temperature (325 °C) resulted in significantly lower conversion as well as selectivity to acrolein. With the use of two additional traps cooled to ? 7 °C, the selectivity to acrolein increased significantly for good catalysts. Copyright © 2010 Society of Chemical Industry     

Shape‐memory behavior of thermally stimulated polyurethane for medical applications

Shape memory polymers (SMPs) have been of great interest because of their ability to be thermally actuated to recover a predetermined shape. Medical applications in clot extracting devices and stents are especially promising. We investigated the thermomechanical properties of a series of Mitsubishi SMPs for potential application as medical devices. Glass transition temperatures and moduli were measured by differential scanning calorimetry and dynamic mechanical analysis. Tensile tests were performed with 20 and 100% maximum strains, at 37 and 80°C, which are respectively, body temperature and actuation temperature. Glass transitions are in a favorable range for use in the body (35–75°C), with high glassy and rubbery shear moduli in the range of 800 and 2 MPa respectively. Constrained stress–strain recovery cycles showed very low hysteresis after three cycles, which is important to know for preconditioning of the material to ensure identical properties during applications. Isothermal free recovery tests showed shape recoveries above 94% for MP5510 thermoset SMP cured at different temperatures. One material exhibited a shape fixity of 99% and a shape recovery of 85% at 80°C over one thermomechanical cycle. These polyurethanes appear particularly well suited for medical applications in deployment devices such as stents or clot extractors. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3882–3892, 2007     

Activity Comparison of Different Solid Acid Catalysts in Etherification of Glycerol with tert-Butyl Alcohol in Flow and Batch Reactors

In the presented work, etherification of glycerol with TBA was investigated in a continuous flow and also in a batch reactor using nine different commercial solid acid catalysts, namely Amberlyst-15, Amberlyst-36, Amberlyst-35, Amberlyst-16, Relite EXC8D, Lewatit K2629, H-Beta, H-Mordenite and Nafion SAC-13. Results proved the advantages of flow reactor to achieve quite high glycerol conversion values in very short residence times, due to efficient contact of reactants with the solid catalyst, which was caused by higher catalyst to reactant ratio within the reactor. Results of batch reactor experiments obtained in the temperature range of 80–200 °C proved the importance of operating temperature on the catalytic performance of these materials. Amberlyst-15, which has the highest Brønsted acidity, gave the highest glycerol conversion at 90–100 °C. However, this material is unstable at temperatures higher than 110 °C. Performances of Amberlyst-36 and Relite EXC8D were the best in the range of 110–150 °C, which started to become unstable at 150 °C. Although the catalytic performance of Nafion-SAC-13 was not as good as Amberlyst type resins at temperatures up to 150 °C, its thermal stability was higher and could be used up to 200 °C. Although Brønsted acidity was the most important property of these materials in the etherification reaction of glycerol, results also proved the importance of diffusion resistance on the observed conversion values, which limited the penetration of glycerol to the active acid sites, especially in the catalysts with smaller pore diameters and at lower temperatures. Increased significance of swelling at higher temperatures, especially with Amberlyst-36 which had lower cross-linking in its structure and less rigidity, contributed to the penetration of the reactants to the active sites. Water produced during the etherification reaction was also shown to cause deactivation of the catalysts by reversible adsorption on the acid sites.     

High‐temperature solution polymerization of butyl acrylate/methyl methacrylate: Reactivity ratio estimation

Solution copolymerizations of butyl acrylate/methyl methacrylate in toluene were performed over an expanded temperature range (60–140°C) compared to more typical ranges that do not exceed 80°C. From a large amount of data collected independently at two laboratories, reactivity ratios were estimated at five different temperatures. The reactivity ratios were estimated from low conversion copolymer composition data using both the error‐in‐variables model method and a nonlinear parameter estimation based on the integrated copolymer composition equation. Using all of the available data, temperature‐dependent expressions were developed for the reactivity ratios and compared to previously published bulk copolymerization values. No significant differences appeared to exist between the bulk and solution polymerization reactivity ratios. Furthermore, the copolymer composition data conformed to the Mayo‐Lewis kinetic model over the entire temperature range. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 602–609, 2000     

Properties of CP: Coefficient of Thermal Expansion,Decomposition Kinetics,Reaction to Spark,Friction and Impact

The properties of pentaamine (5‐cyano‐2H‐tetrazolato‐N2) cobalt (III) perchlorate (CP), which was first synthesized in 1968, continues to be of interest for predicting behavior in handling, shipping, aging, and thermal cook‐off situations. We report coefficient of thermal expansion (CTE) values over four specific temperature ranges, decomposition kinetics using linear and isothermal heating, and the reaction to three different types of stimuli: impact, spark, and friction. The CTE was measured using a Thermal Mechanical Analyzer (TMA) for samples that were uniaxially compressed at 68.95 MPa and analyzed over a dynamic temperature range of −20 °C to 70 °C. Differential scanning calorimetry, DSC, was used to monitor CP decomposition at linear heating rates of 1–7 °C min⁻¹ in perforated pans and of 0.1–1.0 °C min⁻¹ in sealed pans. The kinetic triplet was calculated using the LLNL code Kinetics05, and predictions for 210 °C and 240 °C are compared to isothermal thermogravimetric analysis (TGA) experiments. Values are also reported for spark, friction, and impact sensitivity.     

Change in crystallinity of poly(vinylidene fluoride) due to thermal evaporation

Dielectric properties are reported for thin transparent poly(vinylidene fluoride) (PVDF) films, with thickness less than 1 μm, obtained by the thermal evaporation technique. This technique had to be used with the utmost care and control over the temperature of the evaporation source to obtain transparent, undegraded films of PVDF. Capacitance and loss tangent measurements were carried out on these films in the frequency range of 20 Hz to 1 MHz and the temperature range of 25-160°C. It was found that the maximum in ϵ′-t plots at 1 kHz and tan δ-t plots at 100 Hz for these films appeared at 50 and 35°C, respectively, which are lower temperatures than those reported for solution cast PVDF films. This is attributed to the lowering of crystallinity in the thermally evaporated films. X-ray diffraction studies and IR studies also confirmed these observations. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 225–230, 1997     

Some catalytic properties of silica‐supported base and metal porphyrins for hydrocarbon cracking and hydrogenation

A base porphyrin, etioporphyrin (EPI), has been synthesised and a number of metal–etioporphyrin compounds have been derived from EPI by metal insertion, these being nickel, vanadyl, palladium and platinum. The metal–etioporphyrins were supported on silica gel with loadings of 0.5–5.0% (w/w) to be employed as catalysts for hydrocarbon cracking and to a minor extent for hydrogenation. The porphyrins themselves were characterised using temperature programmed decomposition (TPD), temperature programmed reduction (TPR), mass spectroscopy (MS) and infra‐red (IR) spectroscopy. TPD studies up to 550 °C indicated complete stability and TPR studies (20–500 °C) showed interaction with hydrogen, nickel–EPI and Pd–EPI especially showing strong interaction. MS studies showed that metal insertion had occurred for VO–EPI and Ni–EPI and Pd insertion was demonstrated to have occurred using an analytical method. IR spectroscopy carried out on VO–EPI and Ni–EPI showed an absence of ? NH linkages, again confirming metal insertion. The behaviour of the catalysts for hydrocarbon cracking was studied using 2,2‐dimethylbutane (2,2‐DMB) as the model reactant in the temperature range 440–550 °C and thermally in the temperature range 440–600 °C and at 1 at, m (101.3 kPa) pressure. All porphyrins, even the base porphyrin, exhibited cracking activity and the catalysed reaction had an energy of activation, depending on the porphyrin, in the range 78–113 kJ/mol^?1, compared with a value of 210 kJ mol^?1 for the thermal reaction. The product distribution was dominated by C₁ and C₂ hydrocarbons and is typical of a free radical reaction, the thermal reaction giving a similar product distribution, so that the porphyrin catalyst acts as a free radical initiator. Hydrogenation studies using hex‐1‐ene at 150 °C and at 1 atm. pressure showed that Pd–EPI/SiO₂ was an active and possibly stable hydrogenation catalyst, whereas Ni–EPI/SiO₂ while of only slightly lower activity initially, lost that activity so that the Pd–EPI catalyst was over 16 times more active at the end of a 2 h period. © 2001 Society of Chemical Industry     

The densities of three biodiesel fuels at temperatures up to 300 °C

In order to obtain the densities of biodiesel fuels at temperatures up to 300 °C, a capacitance type liquid level meter was designed to measure the increase in volume of 50 ml of three commercial biodiesel fuels over the temperature range of 20–300 °C. Densities were measured for methyl esters of canola and soy and ethyl esters of fish-oil. The frequency output from the meter was linear with temperature and liquid level. Frequencies were recorded in kHz to within three decimal places and had sensitivities of 0.040 kHz/°C and −2.740 kHz/cm for temperature and submergence depth, respectively. Derived densities were found to be linear with temperature over the measured range. Used in this fashion, the level meter can be considered a precise densitometer with a repeatability of 1%.