Volumetric Device Research Articles

The Measurement of High Pressure Vapour‐Liquid‐Equilibria: Part I: Dynamic Methods

AbstractAccurate measurement of high pressure vapour‐liquid equilibria is a most demanding task and has elicited much effort and ingenuity from researchers. The number and variety of approaches adopted attest to the exacting nature of the task of finding the most reliable, accurate and cost‐effective approach. There is as yet no firm consensus of opinion as to which type of equipment is superior. Each type has its advantages and drawbacks and persuasive advocates. There are few areas of research in chemical engineering or physical chemistry in which so great a variety of equipment and techniques has been reported. The purpose of this publication is to summarize in some detail the equipment and procedures used to measure high pressure VLE and to comment on some of the difficulties common to several methods. In Part I we discuss dynamic measurement methods and refer to a new high‐precision volumetric device we have developed for gas chromatograph calibration for gas mixtures or for gas‐liquid mixtures. In Part II we examine static methods for high pressure VLE measurement and present proposals for a new cell suitable for multiphase equilibrium and volumetric data measurement.A complete survey of the numerous types of equipment used and proposed is not feasible within reasonable length. Good reviews by Tsiklis[1] (1968) and Young[2] (1978) in particular are available, and our emphasis is on more recent developments. This review will be useful to those entering the field or those experiencing problems with a particular type of apparatus.

High‐pressure vapor‐liquid equilibria in the propane‐1‐propanol system

AbstractHigh‐pressure isothermal vapor liquid equilibrium data were measured for the propane‐1‐propanol system at 81.6, 105.2, and 120.1° C in a static equilibrium cell with liquid‐phase sampling by a piston‐driven sampling rod and homogenizing the sample with a static jet mixer. The vapor phase was sampled by releasing it into an evacuated manifold, and the gas chromatograph was calibrated with a new variable volumetric device. Satisfactory modeling was achieved with the combined method (Wichterle, 1978b) using the UNIQUAC equation with equations of state: the group contribution EOS (Skjold‐Jorgenson, 1986), Peng‐Robinson EOS (Peng Robinson, 1976) or the two‐parameter Virial EOS. Differences between the measured and calculated vapor‐phase mole fractions, however, were signficant for the lower pressure regions of the 81.6 and 120.1° C isotherms.UNIQUAC parameters aij, hitherto unavailable, with fairly strong temperature dependence in the 81.6 to 120.1° C range are proposed for the system. The covariance matrix indicated a significant correlation among the parameters. The classical mixing rule interaction parameters, σij, required for the original Peng‐Robinson EOS in the combined method were obtained using the direct method (Wichterle, 1978a) and were temperature‐independent for the isotherms for which the propane was supercritical. The possibility of propane/1‐propanol immiscibility was theoretically examined according to the criteria of Baker et al. (1982). The plots of Gibbs energy of mixing vs. phase mole fractions did not indicate liquid‐phase splitting, but the inferences are EOS‐dependent and must await visual confirmation. Our earlier vaporphase thermodynamic consistency test (1991a) indicated the data for all three data sets not to be inconsistent.

Variations in muscle tone of the human rectum: recordings with an electromechanical barostat

Rectal wall tone (the contractile state of the rectal tunica muscularis) should mediate accommodation and influence rectal emptying. Such changes in tone however can be only inferred from changes in baseline pressure recorded with conventional manometry. We used an isobaric volumetric device, the rectal electromechanical barostat, to quantify variations in tone of the rectal wall in response to feeding and to perturbations in response to the pharmacological agents neostigmine and glucagon. The barostat quantitates muscular wall tone indirectly by measuring its reciprocal, e.g., the volume of air within a flaccid intraluminal bag that is maintained at a constant and preselected pressure, by an electronic feedback mechanism. The barostat as well as a three-channel perfused manometric catheter were positioned in the rectum of 14 healthy volunteers. Three patterns of changes were observed: 1) respiratory fluctuations, 2) rapid volume waves, and 3) slow volume changes. Rectal tone varied little during fasting; rapid or slow changes in intrabag volume were infrequent. Ingestion of a standard meal was followed by a significant decrease in barostat bag volume (85 +/- 6 ml fasting vs. 50 +/- 8 ml fed, P less than 0.05). Pharmacological agents also induced predictable responses; neostigmine decreased bag volume and induced phasic pressure activity, whereas glucagon abolished phasic pressure activity and increased barostat bag volume. Perfused manometric catheters showed no concomitant changes in baseline pressure. We concluded that a rectal barostat measured variations in human rectal tone, which were not recorded by conventional manometric techniques. These changes in rectal tone might have important functional significance.

Chemical Reactions in a Solar Furnace by Direct Solar Irradiation of the Catalyst

Concentrated solar radiation has been used to heat air in a volumetric receiver device. Such a receiver, using a wire mesh arrangement placed in the focal zone, can also be used for carrying out a chemical reaction where the catalyst is heated directly by the concentrated solar beam without any intermediary heat transfer fluid. The advantage of such a concept is that the highest temperature of the whole system is at the reaction site and not on the wall of the reactor or in the heat transfer fluid. Thus, higher conversion efficiencies will be obtained. Moreover, as the reaction site is directly irradiated by a very intense solar flux, photochemically enhanced reactions may result under certain conditions. The disadvantage of the approach is the difficulty in insuring uniform insolation and temperature distribution throughout the catalyst surface. Another problem is that a transparent window is required to seal off the reactants from the environment; this may complicate scaling up of the process. In this communication the authors report the results of preliminary experiments demonstrating that catalysed chemical reactions can be carried out by direct solar irradiation of the catalyst.

High-resolution sorption studies of argon and nitrogen on large crystals of microporous zeolite ZSM-5

High resolution adsorption (HRADS) with argon and nitrogen at 77 K were performed on large crystals of zeolite ZSM-5 using a novel volumetric device. Multi-step isotherms for both adsorptives could be observed for the first time. The micropore filling was followed by low temperature microcalorimetry. Exothermic heats of adsorption were found to be correlated with steps in the adsorption isotherms. Based on results from atom-atom potential energy calculations (AAP) as well as from independent model building it is shown that 24 kinetic adsorbate molecules can be situated in a ZSM-5 unit cell. Localized adsorption is presented as possible filling mechanisms. Experimental results are reasonably interpreted assuming primary filling of narrow channels and secondary adsorption in the wider channel intersections. At least for nitrogen there is evidence for a transition of fluid-like to a solid-like adsorbate phase.

A device for measuring the volume of eggs: description and field evaluation

Investigators often find it necessary to determine the volumes of bird eggs (Hoyt 1979). As direct measurement is usually difficult under field conditions, volume is usually calculated from length and breadth measurements of eggs (e.g., Coulson 1963, Ryder 1975, Mills 1979). However, this technique is not without difficulties. Preston (1 974) discussed the calculation of egg volume from linear measurements and concluded that the use of just two parameters such as length and breadth suffered from significant inaccuracy. However, Coulson (1 963) showed that the prediction of volume from length and breadth of Black-legged Kittiwake Rissa tridactyla eggs produced a maximum error of only 4%, an amount the author found acceptable. We recently required precise, field-determined measurements of the volume of Ring-billed Gull Larus delawarensis and Common Tern Sterna hirundo eggs. Whilst devices for the direct measurement of volume are available (e.g., Loftin & Bowman 1978, Van Noordwijk et al. 1981), we felt that certain design features made them cumbersome and impractical for field use. Accordingly, we undertook to produce a volumetric device of sufficient accuracy and precision that was easy to use in the field, Here, we present a description of the device and the results of field trials designed to contrast egg volume determination using the device, with that from calculation using length and breadth measurements.

Diffusion and adsorption in microporous solids: Measurement of effective diffusivities in coal

The unsteady-state diffusion and adsorption of carbon dioxide was examined using the unsteadystate diffusion equation which included an additional term to account for the adsorption. This allowed a theoretical prediction of the uptake of carbon dioxide which could be compared with the experimental uptake in a static volumetric adsorption device. The solution of this equation also allowed the determination of a diffusion parameter characteristic of each coal. The long equilibrium times experienced experimentally were predicted theoretically by the solution of this equation. Also, the diffusion parameter appears to be a function of the surface area, increasing with increasing surface area.

High-accuracy volumetric device for hydrogen sorption kinetic studies

Describes a set-up designed to study heterogeneous solid-gas kinetics, especially hydrogen sorption by intermetallic compounds of high mass formulae such as LaNi5. The equipment is used in 0-100 degrees C and 0-1.5 MPa ranges.

A mechanical volumetric feeding device for aquaculture research

A simple mechanical feeding device is described which can volumetrically deliver a preset quantity of pelleted or granulated dry fish feed.

Kinetics of hydrogen absorption and desorption by ternary LaNi 5-type intermetallic compounds

Kinetic rules of formation and decomposition of the hydrides derived from LaNi 5-type compounds are determined. Comparison between LaNi 5H 6 and more stable hydrides such as LaNi 5- χ M χ (with M = Al, Cu, Ti) is made in terms of pressure, number and time of cycles. Measurements are performed by a differential volumetric device functioning under constant pressure, during hydrogen absorption and desorption. The influence on the kinetics and hydrogen capacities of the gaseous impurities contained in industrial hydrogen (H 2O, CO 2, CH 4) is studied as a function of the number of cycles. It shows a good resistance to poisoning of the above mentioned compounds.

Collection of oviduct fluid from unrestricted monkeys.

Hamner & Fox (1969) have recently reviewed various techniques for the collection of oviduct fluid in the rabbit, sheep, pig and monkey. Continual collection of the oviduct fluid from the rhesus monkey was first achieved by Mastroianni, Shah & Abdul-Karim (1961). They cannulated the oviducts with silicone rubber tubings which were connected to an external volumetric collection device fixed to the skin. Movements of the animals' upper limbs were restricted with plaster to prevent the animals from reaching the device. Using this technique, daily samples were collected for as long as four complete menstrual cycles. In view of the possibility that a physical restriction of the monkey might cause a deleterious effect on the normal secretory patterns of the fluid, we developed a device which allows daily collection of the fluid from unrestricted monkeys. The device was installed intra-abdominally and samples were taken for a period of over 3 months, after which, however, the device was subject to rejection by the animal. The technique and preliminary data obtained are described in this report.

A simple volumetric device for preparing stool samples in the cellophane thick-smear .echnique.

Abstract We have designed a volumetric device to estimate the weight of stool in the cellophane thick-smear technique; this is a 1-ml plastic syringe sectioned 3 mm from its tip, with a calibrator to ensure a constant displacement of the plunger and hence a constant volume of stool. Statistical analysis showed no significant variation among the weights of stool samples measured in syringes of the same size. There was no significant difference in the weight of 20 random samples when the same syringe and the same calibrator were used. The device is recommended for use in public-health programs on helminthiasis, due to its ease of manufacture, low cost, and reproducibility.

Micro-volumetric respirometry; methods for measuring O2 consumption and CO2 production by cells and enzymic reactions.

When the Arctic Research Laboratory at Point Barrow, Alaska, was ready for use in 1947, it was late autumn. Frost could set in at any time and render unavailable precious material for our projected respiratory studies. This situation brought about an acute need for many more micro than the dozen we had, and prompted the construction of simple, plastic drilled in blocks of lucite. Standard specimen vials attached by rubber stoppers were used as respiration and compensating vessels and tuberculin syringes for the measurements of the oxygen consumption (Scholander, 1950). In a few days our Eskimo friends made enough new to fill our needs. A micro model was similarly constructed and both sizes proved eminently useful on a wide variety of animal and plant material. A model for tissue respiration was designed using standard Warburg vessels. Wennesland (1949) at the same laboratory modified this design to contain an internal rod chamber. The present are a further development of the Barrow respirometers which are all based on the volumetric principle introduced by Winterstein (1912, 1913). In the volumetric system, the pressure is maintained constant, and the volume changes are*read directly. The principle involved can be stated as follows: The pressure of the respiration chamber is balanced against a compensating chamber through a manometer. As gas is absorbed or evolved, it is exactly compensated for by a volumetric device so as to maintain pressure balance with the compensating chamber. The change in gas volume is measured directly on the volumetric device. The volumetric system offers some conspicuous advantages. The volume changes are read directly as such, and are independent of the gas volume of the apparatus. The only calibrated part is the compensating device (piston 375

The volumetric incidence of atmospheric allergens: II. Simultaneous measurements by volumeric and gravity slide methods. Results with ragweed pollen and alternaria spores

1. 1. In obtaining representative samples of the pollen and fungus spore content of the air under the best conditions I could provide, two volumetric devices of totally different design, one of which sampled more than ten times as much air as the other, recovered practically the same number of pollen grains and Alternaria spores per cubic yard of air on a given day. Simultaneously exposed gravity slides caught amounts of pollen and spores varying greatly day by day in comparison to the amounts gathered by the volumetric apparatus. 2. 2. In forty-seven tests over a total period of 337 hours, the average excess of the gravity catch of ragweed pollen over the theoretical standard was more than 100 per cent. 3. 3. The greatest excess catch of ragweed on gravity slides usually occurred on days of highest wind velocity, but the degree of this inaccuracy could not be predicted with any certainty. 4. 4. Rates of fall for various types of pollen grains cannot be calculated from the rate of deposit of air-borne pollen on outdoor gravity slides because of the unavoidable impinging effect of frequent descending wind currents. Therefore the Scheppegrell-Cocke-Dahl tables are of no practical value in converting gravity slide figures to accurate volumetric equivalents. 5. 5. This study shows that over a long period of time, under the special conditions described in this paper, and with average wind velocities of about 10 miles per hour, the average ragweed pollen catch on a gravity slide (1 sq. cm., 24 hours) is approximately one-sixth of the average number of ragweed pollen grains in 1 cubic yard of air. If subsequent experiments in other places with comparable wind velocity should show an average similar proportion, it may be possible to use the following arbitrary conversion factors: 5.97 when the unit area counted on the gravity slide is 1 sq. cm., 3.2 when the unit area is 1.8 sq. cm. 6. 6. Under the conditions enumerated above the average catch of Alternaria spores on a gravity slide (1 sq. cm., 24 hours) is 1 26 as much as the actual average alternaria spore content per cubic yard of air. If subsequent experiments in other places with comparable wind velocity should show an average similar proportion, it may be possible to use the following arbitrary conversion factors: 26.08 when the unit area counted on the gravity slide is 1 sq. cm., 14.5 when the unit area is 1.8 sq. cm. 7. 7. Since no simple volumetric device is yet available for routine atmospheric tests, it may be necessary for some time to continue to rely on gravity slides, but they must be regarded henceforth as being much more inaccurate than many workers have assumed. It is possible that the gravity sampling method can be improved. 8. 8. For volumetric testing the Hawes device is to be recommended for accuracy and simplicity.