Point, dead

Totpunkt, m, dead point, dead center, tot-reif, a. dead ripe, -rosten, t.t. dead-roast, dead-burn, -sicher, a. dead sure, cocksure, Totspulen, n. Petroleum) mudding off, water ing off. 

Biamperometry — Whereas in amperometry the -> current is limited by the electrode process proceeding at one indicator electrode (and the -> counter electrode has no effect), in biamperometry the current flowing between two indicator electrodes is measured, i.e., both electrodes can limit the overall current. This approach is useful in following some -> titrations, and it may lead to zero current (dead-stop) at the equivalence point (dead-stop titration). Example iodine in an iodide solution is titrated with As(III). Two platinum electrodes with a potential difference of around 100 mV prompt iodine to be reduced on one electrode and iodide being oxidized at the other. The two processes maintain an almost constant current until the endpoint when iodine is exhausted. 

Fig. 1 Diagram depicting the retention volume, corrected retention volume, dead point, dead volume, and dead time of a chromatogram. Fq total volume passed through the column between the point of injection and the peak maximum of a completely unretained peak F total volume of mobile phase in the column F (a) retention volume of solute A F (a) corrected retention volume of solute A F extra column volume of mobile phase volume of mobile phase, per theoretical plate vy. volume of stationary phase per theoretical plate distribution coefficient of the solute between the two phases n number of theoretical plates in the column Q column flow rate measured at the exit.

Fig. 1 Diagram depicting the dead point, dead volume, and dead time and retention volume of a chromatogram. Vq is the total volume passed through the column between the point of injection and the peak maximum of a completely unretained peak, is the total volume of mobile phase in the column, V (a)...

The first thing to notice about these results is that the influence of the micropores reduces the effective diffusion coefficient below the value of the bulk diffusion coefficient for the macropore system. This is also clear in general from the forms of equations (10.44) and (10.48). As increases from zero, corresponding to the introduction of micropores, the variance of the response pulse Increases, and this corresponds to a reduction in the effective diffusion coefficient. The second important point is that the influence of the micropores on the results is quite small-Indeed it seems unlikely that measurements of this type will be able to realize their promise to provide information about diffusion in dead-end pores. 

Lead azide is not readily dead-pressed, ie, pressed to a point where it can no longer be initiated. However, this condition is somewhat dependent on the output of the mixture used to ignite the lead azide and the degree of confinement of the system. Because lead azide is a nonconductor, it may be mixed with flaked graphite to form a conductive mix for use in low energy electric detonators. A number of different types of lead azide have been prepared to improve its handling characteristics and performance and to decrease sensitivity. In addition to the dextrinated lead azide commonly used in the United States, service lead azide, which contains a minimum of 97% lead azide and no protective colloid, is used in the United Kingdom. Other varieties include colloidal lead azide (3—4 pm), poly(vinyl alcohol)-coated lead azide, and British RE) 1333 and RE) 1343 lead azide which is precipitated in the presence of carboxymethyl cellulose (88—92). 

A variation to the top-feed dmm filter is the dual dmm filter which uses two dmms of the same size in contact with each other and rotating in opposite directions. The feed enters into the V-shaped space formed on top of the two dmms and the cake that starts forming initially contains coarser particles due to the settling which takes place in the feed zone. This is beneficial to the clarity of the filtrate because the coarser particles act as a precoat. Erom the point of view, however, of the final moisture content of the cake the stratification of the soHds in the cake may lead to somewhat wetter cakes. Utilization of the area of the dmms is poor since there are dead spaces under the two dmms. The primary appHcation of the dual dmm filters is in dewatering coarse mineral or coal suspensions at feed concentrations greater than 200 kg/m. ... 

Depth filters are usually preferred for the most common type of microfiltration system, illustrated schematically in Figure 28. In this process design, called "dead-end" or "in-line" filtration, the entire fluid flow is forced through the membrane under pressure. As particulates accumulate on the membrane surface or in its interior, the pressure required to maintain the required flow increases until, at some point, the membrane must be replaced. The useful life of the membrane is proportional to the particulate loading of the feed solution. In-line microfiltration of solutions as a final polishing step prior to use is a typical apphcation (66,67). 

Type 1 asphalt is the softest type of mopping asphalt with softening points between 68°C and with penetration at 25°C between 18 and 50 mm /10. It is for roof slopes of less the j in. per ft (0.25 per 12). It is also called dead level asphalt and is not commonly used today because of the porosity of the fiber-glass ply felts and the industry recommendation that roof slope a minimum of j in. per ft. 

Distance-Velocity Lag (Dead-Time Element) The dead-time element, commonly called a distance-velocity lag, is often encountered in process systems. For example, if a temperature-measuring element is located downstream from a heat exchanger, a time delay occurs before the heated fluid leaving the exchanger arrives at the temperature measurement point. If some element of a system produces a dead-time of 0 time units, then an input to that unit,/(t), will be reproduced at the output a.s f t — 0). The transfer function for a pure dead-time element is shown in Fig. 8-17, and the transient response of the element is shown in Fig. 8-18. 

A three-state controller is used to drive either a pair of independent on/off actuators such as heating and cooling valves, or a bidirectional motorized actuator. The controller is actually two on/off controllers, each with deadband, separated by a dead zone. When the controlled variable lies within the dead zone, neither output is energized. This controller can drive a motorized valve to the point where the manipulated variable matches the load, thereby avoiding cychng. 

Speed variation is the total variation in speed from the set point and includes both dead band and oscillation. 

The dead point is the position of the peak maximum of an unretained solute. It is not the initial part of the dead volume peak as this represents a retarded portion of the peak that is caused by dispersion processes. The importance of employing the peak maximum for such measurements as dead volume and retention volume will be discussed in later chapters of the book that deal with peak dispersion. 

The dead time (to) is the time elapsed between the injection point and the dead point. 

The corrected retention volume (V r) is the volume of mobile phase passed through the column between the dead point and the peak maximum. It will also be the retention volume minus the dead volume. 

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