Ammonia vapour pressure

Figure 9.2 Ammonia vapour pressure versus temperature...

In 1932, Jannik Bjerrums) started work on ammonia complexes of copper(l) and Cu(II). Some of the results were obtained with more direct techniques, such as measurement of the ammonia vapour pressure over the solution, or solubility of weakly soluble salts in various supernatant solutions. However, most of the work involved determination of the free concentration of ammonia [NH3 ] via measurements with a glass electrode of... 

In non-refrigerated pressure vessels-perhaps cooled by water spray and/or painted with reflecting paint. The storage pressure corresponds to ammonia vapour pressure at ambient temperature. The storage vessels, often referred to as bullets , are usually cylinders capacity is generally low, below about 2001. Non-refrigerated spherical pressure vessels with capacities up to 15001 ammonia have been used [833]. 

Figure 16.1 shows part of a steel tank which came from a road tank vehicle. The tank consisted of a cylindrical shell about 6 m long. A hemispherical cap was welded to each end of the shell with a circumferential weld. The tank was used to transport liquid ammonia. In order to contain the liquid ammonia the pressure had to be equal to the saturation pressure (the pressure at which a mixture of liquid and vapour is in equilibrium). The saturation pressure increases rapidly with temperature at 20°C the absolute pressure is 8.57 bar at 50°C it is 20.33 bar. The gauge pressure at 50°C is 19.33 bar, or 1.9MN m . Because of this the tank had to function as a pressure vessel. The maximum operating pressure was 2.07 MN m" gauge. This allowed the tank to be used safely to 50°C, above the maximum temperature expected in even a hot climate. 

At room temperature and atmospheric pressure ammonia is a colourless, alkaline gas with a pungent smell. It dissolves readily in water. Physical properties are summarized in Table 9.6. The effect of temperature on vapour pressure of anhydrous ammonia is shown in Figure 9.2. 

Ammonia is shipped as a liquefied gas under its own vapour pressure of 114 psig (7.9 bar) at 21°C. Uses are to be found in refrigeration, fertilizer production, metal industries, the petroleum, chemical and rubber industries, domestic cleaning agents and water purification. Aqueous solutions of ammonia are common alkaline laboratory reagents ca 0.88 solution is the strongest available. Ammonia gas is expelled on warming. 

The reaction products were precipitated in methanol containing 0.880 ammonia. The precipitated polymer was filtered off and dried at 50 °C in a vacuum oven. Evaporation of the filtrate yielded the oligomers. For molecular weight determinations, the two fractions were dissolved together in CC14. Molecular weights were determined with a vapour-pressure osmometer. 

To obtain the free aldehyde 25 g. of the aldehyde ammonia are dissolved in 25 c.c. of water, a cooled mixture of water (40 c.c.) and concentrated sulphuric acid (30 c.c.) is added, and the acetaldehyde liberated is distilled from the water bath through a calcium chloride U-tube (gently warmed if the external temperature is low) and through an efficient coil condenser. In order to prevent autoxida-tion of the acetaldehyde the apparatus is filled with carbon dioxide before distillation, and, since the vapour pressure of the aldehyde is high, a slow current of carbon dioxide is passed again, for a short time only, at the end of the distillation. Since acetaldehyde boils at 21° the receiver, which is attached to the condenser by means of a cork stopper, must be well cooled in an ice-salt freezing mixture. 

Perman, E.P. "XLIX — The Influence of Salts and other Substances on the Vapour Pressure of Aqueous Ammonia Solution," J. Chem. Soc., 1902, 81, 480-89. 

At least five different ammino-cuprous chlorides have been described. By studying the vapour pressures obtained by saturating cuprous chloride with ammonia and measuring the vapour pressure between 0° and 150° C., Lloyd found that only three ammino-derivatives existed, namely, hexammino-cuprous chloride, [Cu2(NH3)6]C12 triammino-cuprous chloride, [Cu2(NH3)3]Cl2 monammino-cuprous chloride, [Cu2(NH3)]C12. 

Hexammino-cuprous Bromide, [Cu2(NH3)6]Br2, is made either by saturating finely powdered cuprous bromide with ammonia gas at low temperature,2 or by removing ammonia gas from cuprous bromide which has been saturated with ammonia till the pressure reaches 87-G mm. at 100° C.3 The substance is described by Richards and Merigold as a black, unstable powder, whereas Lloyd describes it as a green powder of melting-point 115° C. The vapour pressure of the salt at 49 3° C. is 760 mm., or, at temperature of 283° C., the dissociation pressure is 100 mm.4... 

Biltz 4 carried out a series of investigations on the vapour pressures of solutions of silver chloride and ammonia, and came to the conclusion that silver chloride forms the triammine, [Ag(NH3)3]Cl, at atmospheric pressure below 20° ., and the sesquiammine, 2AgCl(NH3)3, at temperatures between 20° and 60° C. Above 00° C. silver chloride does not unite with ammonia. 

Diammino-mercuric Iodide, [Hg(NH3)2]I2, behaves like the ammines of zinc and loses ammonia on exposure to air the mon-ammino derivative from examination of vapour-pressure measurements does not appear to exist. 

Table XXV.—The Total Vapour Pressure op Aqueous Solutions op Ammonia at Different Temperatures and Concentrations.

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