Mercury Menisci Research Articles

Voltammetric Behavior of Osmium-Labeled DNA at Mercury Meniscus-Modified Solid Amalgam Electrodes. Detecting DNA Hybridization

The complex of osmium tetroxide with 2,2′-bipyridine has been utilized as a probe of DNA structure and an electroactive marker of DNA in DNA hybridization sensors. It produces several voltammetric signals, the most negative of them has been observed only at mercury electrodes. This signal is of catalytic nature affording a high sensitivity of DNA determination. The catalytic current due to evolution of hydrogen in voltammetry of DNA modified by complex of osmium tetroxide with 2,2′-bipyridine (DNA-Os,bipy) was studied. Solid amalgam electrodes (modified with mercury menisci) of silver (m-AgSAE), copper (m-CuSAE), gold, and of combined bismuth and silver, were used as possible substitutes for mercury electrodes. Besides the hanging mercury drop electrode (HMDE), the catalytic current was observed only on m-AgSAE and m-CuSAE. Electrodes of gold and bismuth amalgams did not give the catalytic current. The detection limit of DNA-Os,bipy on HMDE was 0.1 ng mL−1 (RSD=2.3 %, N=11), and on m-AgSAE 0.2 ng mL−1 (RSD=3.1%, N=11). The m-AgSAE was successfully applied as a detection electrode in double-surface DNA hybridization experiments offering highly specific discrimination between complementary (target) and nonspecific DNAs, as well as determination of the length of a repetitive DNA sequence. The m-AgSAE has proved a convenient alternative to the HMDE or carbon electrodes used for similar purposes in previous work.

The HG5 laser interferometer mercury manometer of the IMGC

Mercury manometers have been designed and constructed at the Istituto di Metrologia "G. Colonnetti" (IMGC) since 1986, their main characteristic being the adoption of cube-corner reflectors, carried by lightweight floats, to reflect the beams of a laser interferometer that measures the vertical separation between the two mercury menisci. The paper describes the most recent instrument, designated HG5, designed to measure up to 120 kPa in either absolute or relative mode. The major improvements introduced in HG5 over its prototype (HG-3) are: the adoption of larger-bore columns; the installation of a single-beam laser interferometer that allows the use of smaller and less intrusive reflecting floats; the improvement of temperature control and measurement; and the development of cat's-eye floats of a novel design allowing the direct reflection of laser beams on mercury menisci. The uncertainty budget and the equations giving the HG5 standard uncertainties (43 mPa to 314 mPa) under all conditions are included.

The MM1 laser interferometer low-range mercury manometer of the IMGC

A compact version, designated MM1, of the HG5 primary standard manometer of the Istituto di Metrologia "G. Colonnetti" (IMGC) is described. The instrument was constructed in order to exploit thoroughly, in the range of pressures up to 5 kPa, the potential accuracy of the measurement principle and instrumentation already adopted in HG5 - the same optical components, instrument hardware and software can be used on either of the manometers. The improvement in measurement accuracy of the MM1 instrument over that of HG5 in the same range was largely obtained by reducing by an order of magnitude the lengths of both mercury and gas columns. This provision can reduce the uncertainties associated with the computation of aerostatic heads in the U-tube and with the correction of interferometer readings for gas refractivity, as well as reduce the detrimental effects of residual temperature gradients inside the manometer body. In addition, the systematic adoption of purpose-built cat's-eye optical devices allows the reflection of laser beams to be made directly on mercury menisci, whereas the massive, all-metal body construction of the manometer ensures an improved mechanical stability. The paper includes the uncertainty budget, with evaluated standard uncertainties ranging between 12 mPa at 1 Pa and 53 mPa at 5 kPa, in the relative or gauge measurement mode.

Evaluation of hysteresis in mercury intrusion porosimetry by second-intrusion method : Cebeci, O Z; Demirel, T; Lohnes, R A Transp Res Rec, N675, 1978, P15–20

The theoretical basis of mercury intrusion porosimetry is reviewed, and the limitations of the Washburn equation as a means of converting the test data to a pore-size distribution curve are discussed. A procedure is suggested to distinguish the volume of pores with uniform radii from the volume of nonuniform of pores. The depressurization curve that results from reducing the pressure on mercury to allow retraction and ejection of mercury from the pores does not coincide with the pressurization curve. This hysteresis is attributed to the presence of ink-bottle or nonuniform pores. Physicochemical factors such as chemisorption and the difference in the contact angle of advancing and retreating mercury menisci contribute slightly to this hysteresis. Consideration of pore geometries demonstrates that the ejection pressure may not be equal to the intrusion pressure for a pore of given size. A comparison of the intrusion, depressurization, and reintrusion of two hypothetical samples illustrates the advantage of the second intrusion for interpreting pore-size distribution curves. The second intrusion gives the distribution of uniform pores and volumes of ink-bottle pores intruded at each entrance diameter. Finally the second-intrusion method is applied to portland cement pastes with a 0.4 water-cement ratio that were hydrated for 3 and 60 d. It is observed that 60 to 64 percent of the porosity is in uniform pores that have a size distribution curve similar to the first-intrusion curve. /Author/

The construction, operation and performance of a primary standard mercury column for the measurement of high pressures

The construction, operation and performance of a primary standard mercury column for the measurement of high pressures

Determinations of the volumes of mercury menisci by means of Röntgen-shadowgraphs

Summary Determinations of the volumes of mercury menisci were made by means of Rontgen-shadowgraphs; the tubes having resp. radii of 3.965, 5.700, 7.845 and 9.422 mm.