Liquid nitrogen trap

Methyl nitrite [624-91-9] M 61.0, b -12 , d (liq) 0.991. Condensed in a liquid nitrogen trap. Distd under vacuum, first trap containing dry Na2C03 to free it from acid impurities then into further Na2C03 traps before collection. 

With the rotary and diffusion pumps in tandem, aided by a liquid-nitrogen trap, a vacuum of 10 Torr became readily attainable between the wars by degrees, as oils and vacuum greases improved, this was inched up towards 10 Torr (a hundred-billionth of atmospheric pressure), but there it stuck. These low pressures were beyond the range of the McLeod gauge and even beyond the Pirani gauge based on heat conduction from a hot filament (limit Torr), and it was necessary to... 

The addition of solid Ba2Xe06 to cold cone H2SO4 produces the second known oxide of xenon, Xe04. This is an explosively unstable gas which may be condensed in a liquid nitrogen trap. The solid tends to detonate when melted but small sublimed crystals have been shown to melt sharply at —35.9°C. Xe04 has only been incompletely studied, but electron diffraction and infrared evidence show the molecule to be tetrahedral. 

Wafers were prepared, sulfided and evacuated (2 h at 673 K) as described above. The temperature was then set at 423 K and 80 kPa of purified deuterium (Air Liquide, N28) was admitted into the cell. The purification procedure consisted of passing the gas through a moisture filter (Chrompack Gas Clean 7971), an oxygen filter (Chrompack Gas Clean 7970) and a liquid nitrogen trap. 

The products were collected after 6 hr reaction at room temperature. The total pressure was 300 mm Hg. Gaseous products were obtained by condensing the gas phase in a liquid nitrogen trap. Surface product was the strongly adsorbed propylene obtained by degassing at 125°C. 

For purification of the product, tubes A and B are cleaned, dried, and reassembled with a dry glass-wool insert in B. Tube C, containing the initially formed product, is attached to tube B as shown in Fig. 2. The system is evacuated and this time left open to the vacuum. The two furnaces are separated by ca. 1.5 cm. Furnace I is heated to 80° and furnace II to 130 to 140°. Sublimation is allowed to continue until all the titanium(IV) iodide has left tube C (12 to 16 hours). The purified product crystallizes in tube B at the separation of the two furnaces. The major impurity, iodine, crystallizes in tube A and in the liquid-nitrogen trap. A fluffy tan residue of negligible weight (0.04 to 0.06 g.) remains in tube C. If desired, further purification can be accomplished by moving tube B farther into furnace II, which results in a second sublimation of the product. 

Lee [524] described a method for the determination of nanogram or sub-nan ogram amounts of nickel in seawater. Dissolved nickel is reduced by sodium borohydride to its elemental form, which combines with carbon monoxide to form nickel carbonyl. The nickel carbonyl is stripped from solution by a helium-carbon monoxide mixed gas stream, collected in a liquid nitrogen trap, and atomised in a quartz tube burner of an atomic absorption spectrophotometer. The sensitivity of the method is 0.05 ng of nickel. The precision for 3 ng nickel is about 4%. No interference by other elements is encountered in this technique. 

To protect the vacuum pump from damage a dry ice-acetone trap and two liquid nitrogen traps are necessary to condense and solidify the hydrogen bromide evolved. 

Certain volatile elements must be analyzed by special analytical procedures as irreproducible losses may occur during sample preparation and atomization. Arsenic, antimony, selenium, and tellurium are determined via the generation of their covalent hydrides by reaction with sodium borohydride. The resulting volatile hydrides are trapped in a liquid nitrogen trap and then passed into an electrically heated silica tube. This tube thermally decomposes these compounds into atoms that can be quantified by AAS. Mercury is determined via the cold-vapor... 

Figure 1. Diagram of apparatus (M) monomer reservoir (F) flow meter (VG) vacuum gage (mercury manometer) (E) electrode (T) liquid nitrogen trap (P) mechanical pump (V,) needle valve (Vt) stop valve (Vs) pressure control valve (OSC) discharge frequency oscillator (AMP) amplifier (1MC) impedance matching circuit...

The volatile material (acetonitrile and the excess of 1-chlorobutane) is captured h a liquid nitrogen trap. This solution (35 wt% in 1-chlorobutane, determined by GC) can be stored in a dark flask and used for further synthesis. 

Backstreaming Measurements above Liquid-Nitrogen Traps Vac. Sci. Tech., Vol. 6,265-268,1969... 

Several volatile components of papaya (Solo variety) were recovered by four methods vacuum trapping train (distillation under low temperatures with liquid nitrogen traps), codistillation-extraction (vacuum), vacuum distillation, and codistillation-extraction (1 atm) [17]. In spite of great variations due to the recovery method, the results showed that linalool was always the major compound detected for all the methods. 

If an alkylammonium salt is desired, it can be obtained by a metathesis reaction. In a typical reaction, 3g of K[B9B14] is dissolved in 30 mL of deoxygenated distilled water, and a solution of 8.8 g of [(C2H5)4N]Br in 20 mL of deoxygenated distilled water is added. A precipitate forms immediately. The solution is filtered and the solid is dried by evacuation using a liquid nitrogen trapped two-stage vacuum pump. The product is obtained in 90% yield. 

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