Mercury separation

In many applications, such as the analysis of mercury in open ocean seawater, where the mercury concentrations can be as small as 10 ng/1 [468,472-476], a preconcentration stage is generally necessary. A preliminary concentration step may separate mercury from interfering substances, and the lowered detection limits attained are most desirable when sample quantity is limited. Concentration of mercury prior to measurement has been commonly achieved either by amalgamation on a noble-metal metal [460,467, 469,472], or by dithizone extraction [462,472,475] or extraction with sodium diethyldithiocarbamate [475]. Preconcentration and separation of mercury has also been accomplished using a cold trap at the temperature of liquid nitrogen. 

To separate mercury from sulphur, it is necessary to seek among our elements a material which has more affinity with the sulphureous acid than mercury has lime is such a species, as it will detach the acid from the mercury by its alkali salt, but as the alkali salt is there in small quantity, it requires three parts of chalk for one of cinnabar, if one operates with tartar or another alkali salt, only equal parts are required. 

All the thus far formalized steps in defining and performing an experiment are being demonstrated in this example. The process of separating mercury from caustic, as part of the process of extraction in a batch reactor with a mixer, is being tested. 

When being cooled in tubular coolers part of the mercury vapour is condensed and the separated mercury is caught in a separator connected with the cooler. After drying with sulphuric acid, hydrogen which now contains 20 to 30 mg of mercury per cu. m. is led for further condensation of the mercury vapour to a condenser cooled by the evaporation of liquid ammonia to — 45 °C. The gas is then filtered by passing through cotton and a layer of activated carbon. The purified hydrogen contains only 0.001 mg of mercury per cu. m. 

Mercury can be separated by the extraction of the iodide complexes with cyclohexanone from an acid medium. Owing to the high stability of Hgl2 and Hgl3 , the stoichiometric ratio of iodide mercury is sufficient [2]. Extraction of the molecular species HgX2 (X = r, Br, Cl ) with non-polar solvents is a very selective method of separating mercury. 

A calixarene dithiocarbamate (4.4) can separate mercury and gold in the presence of lead, cadmium, nickel, and platinum.70... 

A different method of preparation is advisable if the pure, solvent-free organolithium compound is required. In a procedure due to Schlenk and Holtz50 the organolithium compound is prepared from metallic lithium and the organomercury compound in an indifferent solvent since most organolithium compounds, in particular the higher alkyl derivatives, are very readily soluble in hydrocarbons, they can be easily separated from the separating mercury and then obtained pure by evaporation of the solution. 

Although not modified to increased adsorption capacity, the first commercial example was the cobalt chloride-impregnated transition alumina marketed by Alcoa in the 1950s for water adsorption. Calcium, sodium, and potassium salts have also been used commercially for various reasons. The most recent published example is the modified alumina used to separate mercury from natural gas streams in the Arabian oil countries. A related example is the permanganate impregnation of a... 

Nessler s reagent is an alkaline solution of mercuric iodide. Under the influence of aldehydes a red-brown precipitate is formed first which turns gray after a short while from the separated mercury. The reagent gives a similar precipitate with ammonium salts. With ketones a bright yellow precipitate is formed. The same is true of guanidine. The reaction is suitable for the detection of aldehydes in methanol and ether. 

Sodium hydroxide is manufactured by electrolysis of concentrated aqueous sodium chloride the other product of the electrolysis, chlorine, is equally important and hence separation of anode and cathode products is necessary. This is achieved either by a diaphragm (for example in the Hooker electrolytic cell) or by using a mercury cathode which takes up the sodium formed at the cathode as an amalgam (the Kellner-Solvay ceW). The amalgam, after removal from the electrolyte cell, is treated with water to give sodium hydroxide and mercury. The mercury cell is more costly to operate but gives a purer product. 

If the components are colourless, their separation can often be followed by working in a quartz (or special glass) tube which is placed in the light of a mercury lamp. The separate zones are then often revealed by their fluorescence. 

A 1500 ml. flask is fitted (preferably by means of a three-necked adaptor) with a rubber-sleeved or mercury-sealed stirrer (Fig. 20, p. 39), a reflux water-condenser, and a dropping-funnel cf. Fig. 23(c), p. 45, in which only a two-necked adaptor is shown or Fig. 23(G)). The dried zinc powder (20 g.) is placed in the flask, and a solution of 28 ml. of ethyl bromoacetate and 32 ml. of benzaldehyde in 40 ml. of dry benzene containing 5 ml. of dry ether is placed in the dropping-funnel. Approximately 10 ml. of this solution is run on to the zinc powder, and the mixture allowed to remain unstirred until (usually within a few minutes) a vigorous reaction occurs. (If no reaction occurs, warm the mixture on the water-bath until the reaction starts.) The stirrer is now started, and the rest of the solution allowed to run in drop-wise over a period of about 30 minutes so that the initial reaction is steadily maintained. The flask is then heated on a water-bath for 30 minutes with continuous stirring, and is then cooled in an ice-water bath. The well-stirred product is then hydrolysed by the addition of 120 ml. of 10% sulphuric acid. The mixture is transferred to a separating-funnel, the lower aqueous layer discarded, and the upper benzene layer then... 

Pinacol possesses the unusual property of forming a crystalline hexahydrate, m.p. 45°, and the pinacol is separated in this form from the unreacted acetone and the tsopropyl alcohol. The magnciaium is conveniently amalgamated by dissolving mercuric chloride in a portion of the acetone mercury is then liberated by the reaction ... 

Place a mixture of 53 g. of A.R. lactic acid (85-88 per cent, acid), 75 g. (85-5 ml.) of commercial anhydrous isopropyl alcohol, 300 ml. of benzene and 20 g. of Zeo-Karb 225/H (1) in a 700 ml. bolt-head flask, equipped with an automatic water separator (e.g., a large modified Dean and Stark apparatus with a stopcock at the lower end, see Fig. Ill, 126, 1) carrying an efficient reflux condenser at its upper end, and a mercury-sealed stirrer (alternatively, the hquid-sealed stirrer shown in Fig. 11,7,11, c. may be used). Reflux the mixture, with stirring, on a steam bath for 5 hours or until water no longer collects in appreciable amount in the water separator run off the water from time to time. Filter off the resin at the pump and wash it with two 25 ml. portions of benzene. Shake the combined filtrate and washings with about 5 g. of precipit-ated calcium... 

Equip a 500 ml. three necked flask with a reflux condenser, a mercury-sealed mechanical stirrer and separator funnel, and support it on a water bath. Attach an absorption device (Fig. II, 8, 1, c) to the top of the condenser (1). Place 134 g. (152 ml.) of A.R, benzene and 127 g. of iodine in the flask, and heat the water bath to about 50° add 92 ml. of fuming nitric acid, sp. gr. 1-50, slowly from the separatory funnel during 30 minutes. Oxides of nitrogen are evolved in quantity. The temperature rises slowly without the application of heat until the mixture boils gently. When all the nitric acid has been introduced, reflux the mixture gently for 15 minutes. If iodine is still present, add more nitric acid to the warm solution until the purple colour (due to iodine) changes to brownish-red. 

Equip a 1 Utre three-necked flask or a 1 litre bolt- head flask with a reflux condenser and a mercury-sealed stirrer. Dissolve 50-5 g. of commercial 2 4-dinitro-l-chlorobenzene in 250 ml. of rectified spirit in the flask, add the hydrazine solution, and reflux the mixture with stirring for an hour. Most of the condensation product separates during the first 10 minutes. Cool, filter with suction, and wash with 50 ml. of warm (60°) rectified spirit to remove unchanged dinitrochlorobenzene, and then with 50 ml. of hot water. The resulting 2 4-dinitrophenylhydrazine (30 g.) melts at 191-192° (decomp.), and is pure enough for most purposes. Distil oflF half the alcohol from the filtrate and thus obtain a less pure second crop (about 12 g.) recrystallise this from n-butyl alcohol (30 ml. per gram). If pure 2 4-dinitrophenylhydrazine is required, recrystallise the total yield from n-butyl alcohol or from dioxan (10 ml. per gram) this melts at 200° (decomp.). 

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