Mercury distillation

A McLeod gauge must be removed from a system when it is being cleaned. This removal probably will involve the talents of a glassblower. The mercury should be carefully poured out of the gauge and sent to a mercury distiller for cleaning. The grease should be removed by an appropriate solvent. Silicon grease should never... 

Do not eat or keep food in rooms where there is mercury. Mercury distillation is particularly hazardous. The apparatus should be set up in a fume cupboard, preferably over a large tray to contain any spillage. 

This compound, with sodium thiosulphate in alcoholic solution at 70° C.j yields a grey product insoluble in all organic solvents. It is unstable towards nitric add, and when heated to 100° C. in vacuo mercury distils off. 

Mercury boils at 629.7 K, under atmospheric pressure, and Avap/7 =59.27 kJ/mol at that temperature. A mercury distillation plant runs at 673.0 K what is Avap// at that temperature Average values of CP for liquid and vapour are 27.4 and 20.6 J/mol K, respectively. 

FIGURE 11. Use of mercury to dissolve gold in ore concentrates- The gold amalgam is then heated and mercury distills (Ercker, see Figure 5). 

The most important minerals used for the production of mercury are cinnabar and cinnabarite (HgS). Quicklime can be used to flux the ore and combine with the sulfur. At above 300 °C and in the absence of oxygen, the reaction proceeds as in (32.6). In the presence of oxygen, reaction (32.7) occurs. The mercury distils from the retort and is condensed [32.17]. 

Small quantities of Dg are stored in sealed glass flasks or over mercury. Distilled water can also be used as a sealing liquid. Larger amoimts may be condensed in a metal flask cooled with liquid H g. The liquid is then heated and thus forced through metal tubing into small steel cylinders. 

The mercury distils over, and the ferric sulphide remains in the retort. 

Surface mercuiy usually is in the metallic form. Simple washing of the surface can be very effective. High-pressure water can remove mercury quickly splash containment is necessary. Steel and rubber-lined pipework can be retorted or cleaned with HCI/CI2 or NaOH/H2C>2. These solutions oxidize the metal to the soluble Hg +. Heavily contaminated steel will sweat mercury. Lott [19] points out that broken concrete from a cell room floor also can sweat mercury if allowed to stand overnight. Components should be stored with this in mind. Liquid droplets can be collected. The storage area should be ventilated because of evaporation of the mercury. Buswork and copper fabrications are protected by surface films and usually are not seriously contaminated with mercury. Surface washing is good practice before recycle. Copper braid or flexible strips can be more heavily contaminated and require treatment in a mercury distillation oven. 

Friedrich Wohler made critical comments on Oersted s investigation and questioned whether he really had obtained aluminum after the mercury distillation. Careful examinations of Oersted s notes and recapitulations of the original experiments confirmed that Oersted had succeeded in isolating aluminum. In all international tables of element discoverers its is Hans Christian Oersted alone who is attached to the discovery of aluminum. 

Metallic radium was prepared in 1910 by Marie Curie and Andre Debierne. They used 0.1 g of radium chloride and carried out an electrolytic reduction on a mercury cathode. When the liquid amalgam that had been formed was heated, mercury distilled off and elementary radium was isolated. 

As stated above for the TBP distillation, petroleum cannot be heated above 340°C without its molecules starting to crack. Because of this, analytical distillation of heavy fractions is done according to the ASTM D 1160 method for petroleum materials that can be partially or completely vaporized at a maximum temperature of 400°C at pressures from 50 to 1 mm of mercury (6.55 to 0.133 kPa). 

The distillation of crudes chosen for their yield in heavy fractions is the most common means. Bitumen is extracted from the residue from a vacuum distillation column (a few dozen mm of mercury), the latter being fed by atmospheric distillation residue. Unlike the practice of a decade ago, it is now possible to obtain all categories of bitumen, including the hard grades. 

When constructing a manometer of the type shown in Fig. 12(c), it is impor tant to apply a very high vacuum (e.g., with a Hy-Vac pump) to the manometer while the mercury in the left-hand (sealed) limb is heated until it boils unless this is done, traces of air will remain in this limb and cause inaccurate readings. During a distillation, the tap I should be kept closed except when a pressure reading is being taken if it is left open indefinitely, a sudden default by the distillation apparatus or by the pump may cause the mercury in the sealed limb of G to fly back and fracture the top of the limb. 

The distillation heads Fig. 22(F) and Fig. 22(G) can be fitted with thermometers having a ground-glass cone just above the bulb (Fig. 22(M)). These are expensive, and it is usually more convenient to fit a thermometer pocket (Fig. 22(N)) which consists of a small well , fitting as shown into the neck of the flask. A small volume of mercury is placed in the well just to cover the bulb of a conventional thermometer, and thus provides excellent thermal contact between the thermometer and the sides of the pocket. 

The so-called hydro-vac pump, shown in Fig. 11, 22, 2 (the upper half of the mercury reservoir and the column above it are insulated by a layer of asbestos), is an inexpensive, all-glass, mercury diffusion pump, which can be used in series either with an oil pmnp or with a water Alter pmnp (compare Fig. 11,21, 1) capable of producing a vacuum of at least 2 mm. It is accordingly of particular value in the organic laboratory for vacuum distillations, fractionations, sublimations and pyrolyses as well as for molecular distillations (see Section 11,26). The hydro-vac... 

In molecular distillation, the permanent gas pressure is so low (less than 0 001 mm. of mercury) that it has very little influence upon the speed of the distillation. The distillation velocity at such low pressures is determined by the speed at which the vapour from the liquid being distilled can flow through the enclosed space connecting the still and condenser under the driving force of its own saturation pressure. If the distance from the surface of the evaporating liquid to the condenser is less than (or of the order of) the mean free path of a molecule of distillate vapour in the residual gas at the same density and pressure, most of the molecules which leave the surface will not return. The mean free path of air at various pressures is as follows —... 

If preferred, the following alternative procedure may be adopted. The absolute alcohol is placed in a 1 5 or 2 litre three-necked flask equipped with a double surface reflux condenser and a mercury-sealed mechanical stirrqr the third neck is closed with a dry stopper. The sodium is introduced and, when it has reacted completely, the ester is added and the mixture is gently refluxed for 2 hours. The reflux condenser is then rapidly disconnected and arranged for downward distillation with the aid of a short still head or knee tube. The other experimental details are as above except that the mixture is stirred during the distillation bumping is thus reduced to a minimum. 

Upon distilling the mercury compound with concentrated hydrochloric acid, it is readily decomposed into mercuric chloride and pure thiophene. 

Allyl cyanide. Into a 1 5 litre three-necked flask (1), provided with a mercury-sealed stirrer and two long double surface condensers, place 293 g. (210 ml.) of freshly-distilled allyl bromide, b.p. 70-71° (Section III, 35) and 226 g. of dry cuprous cyanide (Section 11,50,3, Method 1), Remove the mercury-sealed stirrer and replace it by a tightly fitting... 

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