Diffusion of mercury

Also, the hydrogen evolution overpotential may be decreased when using this type of MFE. The mercury film thickness can be easily regulated by electrolytic deposition with a coulometric control. When the film is relatively thick, its thickness along the MFE surface may not be uniform. MFEs are not stable in time when the mercury film thickness is very low, due to the diffusion of mercury into the metallic support. 

The loss of mercury from water samples on storage has been shown to be a serious problem by many workers [24—26]. These losses of mercury are caused by rapid adsorption on container walls [25, 29] and reduction of mercury to the atomic state followed by volatilization from solution [29], Lo and Wai reported that 81% of mercury in untreated samples was lost to the walls of the polyethylene containers and the remaining 19% was volatilized to the atmosphere [29], Bothner and Robertson observed mercury contamination of seawater samples due to the diffusion of mercury vapor from the laboratory into the polyethylene containers [31]. 

Contamination of aqueous solutions by diffusion of mercury vapour from the ambient air into plastic containers has also been reported (Bothner and Robertson, 1975 Cragin, 1979 Heydorn and Damsgaard, 1982). The rate of contamination was considerably increased (several /solutions contained oxidizing preservatives, such as nitric acid or potassium permanganate. 

Another study of the same type (106) was made of the diffusion of mercury into single crystals of cadmium or zinc. In both cases the diffusion was a maximum parallel to the basal planes and a minimum perpendicular to them. On the basal planes mercury drops gave circular diffusion, while all other... 

A student has left a volumetric flask (shown in Figure 6.10) partially filled with mercury. Compute an expression for the rate of diffusion of mercury vapor into the room. The sides of the flask are tapered so that the stagnant diffusion section is a firustum of a cone (r is a linear function oi z). A shell balance approach should be used. 

From the rate of diffusion of radioactive Pb in molten lead, Andrade estimated that it takes an atom about 2 X 10 u second to move a distance equal to its own diameter.1 If the period of atomic vibration is 5 X 10 ,s second, this time is equivalent to idK)lit 40 atomic vibrations. From the considerations brought forward by Andrade, it appears that the same estimates would apply to liquid mercury above its melting point—that is, near room temperature. When we ask how often the particles of such a liquid change neighbors, it is clear that the rate of turnover is extremely large. If, for example, in (37) we set r0 equal to 1010 second, the chance that two particles remain in contact for as long as 7 X 10-10 second is less than one in a thousand. 

Reference device, use of mercury for, 16 Relaxation and diffusion components in polymer formation, 397... 

The prepared flask is supported so that the tube B can be sealed to a vacuum system. If a suitable furnace is available the flask is surrounded by this, with the constriction A still within reach of the hand torch flame otherwise the heating must be done by flame. A liquid air trap is included between the flask and diffusion pump. With a vacuuih of below 10 mm of mercury the temperature of the flask is raised to near the softening point—the heating may be rapid... 

Fig. 5.46 The dependence on time of the instantaneous current / at a dropping mercury electrode in a solution of 0.08 m Co(NH3)6C13 + 0.1 m H2SO4 + 0.5m K2S04 at the electrode potential where -7 -/d (i.e. the influence of diffusion of the electroactive substance is negligible) (1) in the absence of surfactant (2) after addition of 0.08% polyvinyl alcohol. The dashed curve has been calculated according to Eq. (5.7.23). (According to J. Kuta and I.

May et al. [45] used radiochemical studies to ascertain the behaviour of methylmercury chloride and mercuric chloride in seawater under different storage conditions. The application of 203Hg unambiguously revealed that the loss of mercury observed upon storage of unacidified seawater samples in polyethylene bottles was due to adsorption and to the diffusion of metallic Hg (Hg°) through the container wall. 

A solution was placed in the vessel, CDE, and drops of mercury from A and B allowed to fall through the solution for some hours, the head of mercury being maintained nearly constant. The mercury collected in E and, as the drops coalesced, the surface was reduced and the adsorbed substancejliberated. The constriction at F was provided to prevent diffusion of this released substance backwards into C. It was found that the equilibrium was attained, i.e., that the drops had adsorbed the maximum amount of solute, if they took about six seconds... 

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