Particle charge measurement

Hendricks (H5) and Cho (C2, Method No. 1) both measured particle charge by measuring the voltage pulse on an oscilloscope due to the passage of a charged particle through a drift tube detector. The particle mass was... 

Recent advances made in measuring particle charge and mobility in nonaqueous suspensions are reviewed. Microelectrophoretic techniques have been used to determine zeta potential and the measurements related to particle stability. 

Recently, great strides have been made in developing electrical and optical transient methods for measuring particle charge and mobility in these nonaqueous dispersions. It has been possible to obtain particle charge/mass ratios as well as the field dependence of particle mobility. 

Figure 3-11 shows the experimental setup for measuring particle charge in the freeboard of a circulating fluidized bed fabricated from either copper or... 

If the loose or diffuse double layer is removed, for example, by shearing, charge measurement becomes possible. However, the charge is slightly reduced by the dense layer surrounding the particle. This weakened and measurable particle charge is termed Zeta Potential. 

There are a number of experimental methods to measure particle charge, but most, if not all of them, fall into one of two categories those based on electrophoresis, which measure the net particle charge, and acid-base titrations, which determine proton charge. 

Time-of-flight experiments are used to measure particle velocities and particle mass per charge. The typical experiment... 

Gady found that, depending on the charge of the particle, van der Waals forces dominated over the forces associated with electrostatically charged patches when the particle-to-substrate separation was between 3 and 10 nm, depending on the particle charge. In addition, he found that the distance at which the snap-together occurred required that van der Waals forces dominate over electrostatic. In all his measurements, however, a component of the total attractive force, even at close separations, was observed to be electrostatic in nature. 

Zeta potentials of floe produeed in the plant may also be measured as a means of eontrol. The zeta potential value for optimum eoagulation must be determined for a given wastewater by aetual correlation with jar tests or with plant performance. The control point is generally in the range of 0 to 10 millivolts. If good correlations can be obtained between some zeta potential values and optimum plant performance, then it is possible to make rapid measurements of particle charge to compensate for major variations in wastewater composition due to storm flows or other causes. 

Rutherford found that a second type of radiation was attracted to the positively charged electrode. He proposed that this type of radiation consists of a stream of negatively charged particles. By measuring the charge and mass of these particles, he showed that they are electrons. The rapidly moving electrons emitted by nuclei are called (3 particles and denoted (3". Because a (3 particle has no protons or neutrons, its mass number is 0 and it can be written Je. 

The zeta potential is a measurable indication of the apparent particle charge in the dispersion medium. When its value is relatively high, the repulsive forces usually exceed the attractive forces. Accordingly, the particles are individually dispersed and are said to be deflocculated. Thus, each particle settles separately, and the rate of sedimentation is relatively small. The settling particles have plenty of time to pack tightly by falling over one another to form an impacted bed. The sedimentation volume of such a system is low, and the sediment is difficult to redisperse. The supernatant remains cloudy even when settling is apparent. 

The velocity of particle migration, v, across the field is a function of the surface charge or zeta potential and is observed visually by means of an ultramicroscope equipped with a calibrated eyepiece and a scale. The movement is measured by timing the individual particles over a certain distance, and the results of approximately 10-15 timing measurements are then averaged. From the measured particle velocity, the electrophoretic mobility (defined as v/E, where E is the potential gradient) can be calculated. 

Proportional counters measure the charge produced by each particle of radiation. To make full use of the counter s capabilities, it is necessary to measure the number of pulses and the charge in each pulse. Figure 9 shows a typical circuit used to make such measurements. 

The proportional counter measures the charge produced by each particle of radiation. 

The sizes of charged and neutral particles were measured as a function of increasing temperature (Fig. 18) [178]. The thermal collapse of the PVCL particles turned out to be a more or less continuous process, regardless of particle charge and the presence or absence of amphiphilic grafts. The PEO chains bound to the particle surfaces had only a minor effect on the transition temperature. The sizes of the particles in cold water varied from sample... 

Microelectrophoresis (electrophoretic mobility) . This involves the measurement of particle charge in an applied field. For paper furnishes, the supernatant solution—which contains finely divided colloidal matter, is usually removed and used to conduct the measurement. It must be questioned therefore as to how reflective this is of the charge characteristics of the larger particles and fibres which settle. However, as it is the colloidal fraction which requires to be flocculated to assist retention during drainage, it is still a useful measurement. 

The first modern atomic theory was developed by John Dalton and first presented in 1808. Dalton used the term atom (first used by Democritus) to describe the tiny, indivisible particles of an element. Dalton also thought that atoms of an element are the same and atoms of different elements are different. In 1897, J. J. Thompson discovered the existence of the first subatomic particle, the electron, by using magnetic and electric fields. In 1909, Robert Millikan measured the charge on the electron in his oil drop experiment (electron charge = -1.6022 x 10-19 coulombs), and from that he calculated the mass of the electron. 

N, e Parameter that measures effect of particle slip as corrected for particle charge, dimensionless (see Eq. 19)... 

Suzuki, S., and Tomura, M., Studies on the measurement of charges on fine particles. I. Charge measurement of tobacco and mosquito incense aerosols by a charge spectrometer, Denshi Shashin Japan) 4, No. 2, 20 (1962). 

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