Silver wool

Watling [491] has described an analytical technique for the accurate determination of mercury at picogram per litre levels in fresh and seawater. Mercury, released by tin (II) chloride reduction of water samples is amalgamated onto silver wool contained in quartz amalgamation tubes. The wool is then heated and the mercury thus released is flushed by argon into a plasma where it is excited. The emission signal thus produced results in a detection limit of 3 x 10 17 g and an analytical range 1 x 10 14 g-1 x 10"7 g. 

After the brake-pad introduce a pad, 2 cm. long, of silver wool, preferably formed beforehand in an old combustion tube so that the fit is rather right and pressure on the brake-pad is avoided. Fix the silver wool in position with a small, loose pad of asbestos and, with continuous turning and gentle sidewards tapping of the tube (not jolting ), pour in a layer 14 cm. long, of copper oxide-lead chromate. Fix this also in position with a loose asbestos pad. 

Diiodomethane [75-11-6] M 267.8, m 6.1", b 66-70"/ll-12mm, d 3.325. Fractionally distd under reduced pressure, then fractionally crystd by partial freezing, and stabilized with silver wool if necessary. It has also been purified by drying over CaCl2 and fractionally distd from Cu powder. 

Sulphur dioxide can be removed at 450° using silver wool combined with a plug of platinized quartz wool. Halogens are removed by using Mg, Zn or Cu, heated to 450°. 

The S4N4 is pumped in u vacuum line over silver wool al 220 °C, where it polymerizes slowly lo a lustrous golden material.w The resulting product is analytically pure, as is necessary for it to show metallic properties to a significant degree it has a conductivity near that of mercury at room temperature, and it becomes a superconductor al low temperatures (below 0 26 Kl. 

One to two grams of tetrasulfur tetranitride is placed in A, and a 7-cm.-long plug of finely pressed silver wool is pushed into that part of the tube which is to be heated by Hz. Silver-plated glass wool or copper wool may be used, but the yield will be much lower. The apparatus is then evacuated, trap Ti (200 ml. content) is cooled with a methanol-carbon dioxide mixture to —80°, and trap T2 is surrounded with liquid nitrogen. H2 may then be heated, and when this has attained 300°, Hi may be heated as well. 

When the heated vapor of S4N4 is passed over silver wool at 520 to 570 K, the unstable cyclic dimer S2N2 is obtained. It forms large colorless crystals which are insoluble in water but soluble in many organic solvents. 

Improved reaction. Conia et al. have reported two modifications of the Simmons-Smith reaction which ave improved yields. One is the use of a zinc-silver couple in place of the zinc copper couple. This couple is prepared by adding granular zinc to a stirred hot solution of silver acetate in acetic acid. The mixture is stirred for 30 sec. and the zinc-silver couple formed is isolated by decantation and washed with acetic acid and ether. It is then stabilized by addition of a small amount of silver wool. The second improvement is that the reaction mixture is not subjected to acid hydrolysis. Instead an amine, for example pyridine, is added. This forms the insoluble complexes Znlj-C HsN and ICH jZnl -(C, 115N)j the cyclopropane products are then isolated from the filtrate. 

The is pumped in u vacuum line over silver wool al 22Q C. where k polymerizes... 

A method has been proposed which is amenable for use for sampling of all atmospheres for merciuy in all forms (5). The method as it has been used does not allow for the differentiation between the various forms of airborne mercury possible. Ambient air is drawn over silica wool held at a temperature of 400°C and then passed through silver wool by a pump. The combined species of mercury, if present, are pyrolyzed on the silica... 

Off to the right is a very good thermometer. The openings on the shield should be pointed away from you, so you cannot see the scale if you are sitting directly in front of the apparatus. This is done so you must first decide if the crystals are melting, then read the temperature. It keeps you honest. The bulb of the thennometer is imbedded in silver wool for better heat transfer. 

The reaction starts easily the addition of a crystal of iodine is not necessary. To minimize the formation of hexadiene, the addition of ally I bromide must be slow enough to maintain the temperature of the flask below the boiling point of ether. Allyl bromide (Fluka "purum") even when stored in 1he dark in the presence of silver wool contains some high-boiling material and must be purified by distillation. Pure product (bp 71 °C) is used just after distillation. 

Geraniol is converted into atmospheric pressure phenethyl alcohol gives phenylacetaldehyde cinnamaldehyde is obtained from cinnamyl alcohol in good yield by use of a silver catalyst at 200°/20 mm.429 Bremner et al.43° describe a laboratory method for oxidation of tetrahydrofurfuryl alcohol by air on silver wool. 

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