Mercury loss with time

Samples for mercury analysis should preferably be taken in pre-cleaned flasks. If, as required for the other ecotoxic heavy metals, polyethylene flasks are commonly used for sampling, then an aliquot of the collected water sample for the mercury determination has to be transferred as soon as possible into glass bottles, because mercury losses with time are to be expected in polyethylene bottles. 

In order to understand the full extent of the mercury problem in these times, one has only to consider the enormous loss rates. From the total of 2865 tons of mercury purchased in the U.S. in 1968, 76% or 2160 tons were lost to the environment. According to calculations of Kemp et al. (1974), the Lake Ontario reservoir contained a mass of 500 to 600 metric tons of "excess" mercury, i.e. discharged from anthropogenic sources. With the improvements in the methods of chlor-alkali electrolysis and by subsequent purification of waste streams the mercury loss has been reduced from 100 g per metric ton of manufactured chlorine to approx. 2 g per ton or less (Anon., 1973). The effect of these measures can be seen from concentration profiles of mercury in sediment cores taken off the mouth of Niagara River by Mudroch (1983), where a very distinct decrease from formerly approx. 4-7 ug Hg/g to less than lug Hg/g in recent years has occurred (Figure 2-6). 

Mercury can be a cumulative poison, which means that minor amounts absorbed over long periods of time build up until damage to internal organs occurs. Years ago, a mercury compound was used in the manufacturing process of felt hats. Workers who came in contact with the mercury developed a variety of medical problems, including the loss of hair and teeth and loss of memory along with general deterioration of the nervous and other systems. This became known as the mad as a hatter syndrome because of the afflicted individuals odd behavior. 

Free Mercury. To the insoluble matter, obtained as described in paragraph 112.6, add 2ml of hot concentrated HCl, allowing this to remain for 1 minute prior to removal by suction. Subject the insoluble matter to this treatment three times, wash with hot water, alcohol ether, and weigh. Repeat the procedure until the loss in weight is less than 0.0003g. To the residue add three successive 2-ml portions of hot dilute nitric acid (1 1) in the same manner as with the HCl. Wash the residue with hot water, alcohol ether, and weigh. Calculate the loss in wt as % of metallic mercury... 

In 1908, Kamerlingh Onnes succeeded in liquefying helium, and this paved the way for many new experiments to be performed on the behaviour of materials at low temperatures. For a long time, it had been known from conductivity experiments that the electrical resistance of a metal decreased with temperature. In 1911, Onnes was measuring the variation of the electrical resistance of mercury with temperature when he was amazed to find that at 4.2 K, the resistance suddenly dropped to zero. He called this effect superconductivity and the temperature at which it occurs is known as the (superconducting) critical temperature, Tc. This effect is illustrated for tin in Figure 10.1. One effect of the zero resistance is that no power loss occurs in an electrical circuit made from a superconductor. Once an electrical current is established, it demonstrates no discernible decay for as long as experimenters have been able to watch ... 

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