Evaporation of ammonia

With ammonia, when it is hot, calcium becomes incandescent. When it is cold, in liquid ammonia, a harmless solution is created. However, the evaporation of ammonia leaves calcium powder, which is extremely reactive. It combusts violently and instantaneously in contact with air. 

During its synthetic use in liquid ammonia, some of the salt separated as a crust owing to evaporation of solvent, and exploded violently. Such salts are stable in solution, but dangerous in the solid state. Evaporation of ammonia must be prevented or made good until unreacted salt has been decomposed by addition of ammonium chloride [1]. An improved preparation of the lithium derivative is available [2],... 

Aono, K. et al., J. Chem. Soc., Dalton Trans., 1981, 1190-1195 In the preparation of l,T-azo-2-R-l,2-dicarbadodecaborane(14) by oxidation of the aminocarbaborane anions in liquid ammonia, toluene or other inert solvent must be added before evaporation of ammonia to prevent explosions. Individually indexed compounds are ... 

The dissolution of sulfur in ammonia has been known for more than 100 years [17]. The identification of the chemical species in these solutions was a matter of confusion until the identification of S4N and 83 , by Chivers and Lau [18] and Bernard et al. [19], using Raman spectroscopy. When considering the species formed in the dissolution process, it is quite remarkable that this dissolution is reversible sulfur is recovered after evaporation of ammonia. These solutions are strongly colored (blue), mainly due to the electronic absorption band of S4N at 580 nm. It must be mentioned that this dissolution is moderately fast at room temperature (but much slower than the dissolution of alkali metals) and that the rate is much slower when temperature decreases. It should also be mentioned that concentrated solutions of sulfur in liquid ammonia can be used as the solution at the positive electrode of a secondary battery. The solution at the negative electrode can be a solution of alkali metal in liquid ammonia [20], the electrodes being... 

After evaporation of ammonia, and after drying under high vacuum, the M28 solid is obtained. The dissolution of the solid M28 in a given solvent can also be obtained directly in the solvent by the reaction of sulfide M2 8 with ( — 1) 8. 

Liquid ammonia is not a classical solvent for sulfur because it dissolves sulfur in the course of a reversible and slow disproportionation process as has been described earlier. Ammonia is a very useful solvent for the investigation of polysulfides because it allows their synthesis with an easy control of their stoichiometry. After evaporation of ammonia and drying under high vacuum, a solid with the overall composition M28 is obtained. The solid is either a polysulfide or a mixture of polysulfide (s) with sulfur, depending... 

Thanks to the relatively high heat of evaporation of ammonia, many reactions can be carried out at its boiling point, -33 C. The use of a dry ice-acetone reflux condenser is absolutely unnecessary. Losses due to evaporation are easily compensated by adding ammonia from the cylinder. The rate of evaporation can be limited by insulating the flask with cotton wool the ice which forms on the outside of the flask as a result of condensation can, to some extent, have a similar function. 

We have developed a model to take into account these evaporation processes (for more details, in particular kinetic equations, see ref 27) that can be both applied to phenol and naphthol, The main idea is the following the excited state decays observed correspond to evaporation of ammonia molecules after excitation of ground state proton transferred naphthol-(NH3) >6 clusters. As in the case of phenolate [31], a strong change in dipole... 

Ammonia solution (concentrated). The commercial concentrated ammonia solution is a water-like liquid with a characteristic smell, owing to the evaporation of ammonia gas. It has a density of 090 gem-3, contains 58-6% (w/w) NH3 (or 0-53 g NH3 per ml), and is approximately 15 1 molar. It should be handled with care, wearing eye protection. Direct smelling of the solution should be avoided. The solution should be kept far apart from concentrated hydrochloric acid to avoid the formation of ammonium chloride fumes. 

An area which deserves special attention with respect to safety is the storage of liquid ammonia. In contrast to some other liquefied gases (e.g., LPG, LNG), ammonia is toxic and even a short exposure to concentrations of 2500 ppm may be fatal. The explosion hazard from air/ammonia mixtures is rather low, as the flammability limits [1334]-[1338], [1343] of 15-27% are rather narrow. The ignition temperature is 651 °C. Ammonia vapor at the boiling point of-33 °C has vapor density of ca. 70% of that of ambient air. However, ammonia and air, under certain conditions, can form mixtures which are denser than air, because the mixture is at lower temperature due to evaporation of ammonia. On accidental release, the resulting cloud can contain a mist of liquid ammonia, and the density of the cloud may be greater than that of air [1334]-[1344], This behavior has to be taken into account in dispersion models. 

The pH can also be controlled by evaporation of ammonia. For example, barium chromate can be precipitated in the presence of strontium and lead by first complexing the metal ions at a pH of 10.4, followed by evaporation of ammonia. The pH decreases slowly, and barium chromate precipitates since the barium ion is no longer complexed at the lower pH. ... 

Silver azide is soluble in ammonia to form a complex, upon evaporation of ammonia the azide is recovered unchanged. In nitric acid it dissolves with de-composition and the evolution of HNa- On exposure to light silver azide turns first violet and finally black, as colloidal silver is formed and nitrogen evolved J [3 (Vol. l,p.58)). 

Reduction of derivatives of estradiol 3-methyl ether (I) and hydrolysis of the initially formed enol ether II provides an efficient route to 19-norsteroids (111) of considerable importance in hormone therapy. A. J. Birch, who introduced the method (1949), used sodium in liquid ammonia with ethanol as proton donor. A. L. Wilds and N.A. Nelson (1953) found that yields are improved by use of lithium in place of sodium and that lithium is effective in some cases where sodium is not. The Wilds-Nelson procedure, which became the standard one, employs ether as co-solvent and involves adding the ethanol lust terminal decomposition is done with water after evaporation of ammonia, Since this reaction is the key step in processes developed by O. D. Searleand Co. for the production of two I V-norsteroids... 

To a dark red solution of sodium bis(4-chlorophenyl)bismuthide, prepared from bis(4-chloro-phenybiodobismuthine (2.8 g, 5 mmol), sodium (0.23 g, 10 mmol) and liquid ammonia (150 ml), was added 1-iodonaphthalene (1.27 g, 5 mmol) in ether (10 ml). Evaporation of ammonia... 

A classic method for generating regio-defmed enolates is metal-ammonia reduction of an enone. Stork and d Angelo found that the enolate resulting from lithium-ammonia-r-butyl alcohol reduction of octalone (3), followed by evaporation of ammonia, suspension of the enolate in ether and treatment with... 

Ammonia solution (concentrated). The commercial concentrated ammonia solution is a water-like liquid with a characteristic smell, owing to the evaporation of ammonia gas. It has a density of 0.90gcm contains 58.6% (w/w) NH3 (or... 

Cellulose IIIt and IIItt. Native cellulose and cellulose II, described above, were treated with liquid ammonia for about 2 hours at about - 80°C. Gradual evaporation of ammonia was permitted in dry air at about - 15°C. 

If dry, ammonia-free amide is desired, the stirrer and condenser are removed from the reactor and replaced by wellfitting rubber stoppers, one of which carries a delivery tube. At this point some of the iron catalyst and the more soluble impurities could be removed simply by decanting the supernatant liquid, which would then require caution in disposal. In any case, the reactor is allowed to stand in a well-ventilated hood overnight for evaporation of ammonia. Outward flow of ammonia prevents access of air to the amide, but a drying tube filled with barium oxide may be used as an added precaution. Next day, a vacuum is drawn on the residue for 10 to 30 minutes, and the vacuum is broken with dry nitrogen gas, which is then led through... 

To 35 0 mL of liquid ammonia, (2.0-2.3 mmol) 4-chloro-3-nitropyridine and double the amount (4-4.6 mmol) of potassium permanganate were added, and the mixture was stirred for 5 h. After evaporation of ammonia, 50 mL of water was added to the residue, and the mixture was continuously extracted with chloroform for 20 h. 

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