Ammonia hydrates

In August 2006, the International Astronomical Union redefined the term planet and decided that the former ninth planet in the solar system should be referred to as a dwarf planet with the number 134340. The dwarf planet Pluto and its moon, Charon, are the brightest heavenly bodies in the Kuiper belt (Young, 2000). The ratio of the mass of the planet to that of its moon is 11 1, so the two can almost be considered as a double planet system. They are, however, quite disparate in their composition while Pluto consists of about 75% rocky material and 25% ice, Charon probably contains only water ice with a small amount of rocky material. The ice on Pluto is probably made up mainly of N2 ice with some CH4 ice and traces of NH3 ice. The fact that Pluto and Charon are quite similar in some respects may indicate that they have a common origin. Brown and Calvin (2000), as well as others, were able to obtain separate spectra of the dwarf planet and its moon, although the distance between the two is only about 19,000 kilometres. Crystalline water and ammonia ice were identified on Charon it seems likely that ammonia hydrates are present. 

The 3-4 Cals, here represent the heat of admixture of a mol of ammonia with water, and this is much greater than the heat of admixture of ammonia with other liquids which do not react chemically with the ammonia. There is also a possibility that ammonia hydrates. NH3.nH20, are formed, vide infra and a possibility that the ammonium hydroxide is ionized NH OH NH +OH. In agreement with the assumption that ammonium hydroxide is formed which acts as a weak base, the liquid tastes alkaline it reddens turmeric colours the juice of violets green and colours litmus, etc., the same as do soln. of the alkali hydroxides. These changes of colour disappear on exposure to air owing to the volatilization of the ammonia— the volatile alkali of the early chemists. The feeble character of ammonium hydroxide as a base is evidenced by its heat of neutralization with acids which is about 1-5 Cals, less than is the case with potassium or sodium hydroxides like other weak bases, the soln. cannot be satisfactorily titrated with phenolphthalein S. Arrhenius found that its effect on the hydrolysis of ethyl acetate is about 40 times leBS than that of sodium hydroxide and the electrical conductivity of aq. soln. of... 

There are two possibilities of formation of hydrogen bonds in the solution of ammonia in water N — H. . . O and N. . . H — O. The latter case is realized in agreement with expectation in fact nitrogen is a better acceptor (more strongly basic) than oxygen, the OH group a stronger donor (more acidic) than NH. Therefore, ammonia hydrate occurs in a solution of ammonia but ammonium hydroxide does not exist (Van Velden and Ketelaar) 15. 

When we adopt the idea that water was carried by icy ammonia hydrate bodies to the earth not only at the very beginning of the earth s formation around 4.6 Gy ago but also during the LHB 4 Gyr ago - when the oceans had already been recycled by the hot surface together with evaporation of dissolved species - there was competition between NH3 photolysis, an irreversible transformation process into N2 (no abiotic process is known on earth that produces NH3 and CH4 under natural conditions), and NH3 scavenging by rain. It also remains open to speculation how much of the ammonia was probably produced from nitrides. 

Lunine, J. L, S. K.Croft and J. Kargel (1988) Clathrate and ammonia hydrates Physical chemistry and applications to the solar system. NASA Technical Memorandum, NASA TM-4041, pp. 135-137... 

Fig. 7.1.2 Near infrared spectrum of Charon (Fig. 3 of Brown Calvin, 2000). The histogram gives the data scaled to the albedo of Charon (Roush et al., 1996). The dashed line is a model consisting of only water ice and a dark neutral absorber. The solid line is a model in which ammonia and ammonia hydrate ices have been added to the water ice and dark absorber model.

In 2007 the Gemini observatory detected patches of ammonia hydrates and water crystals on Charon s surface. This may be explained by active cryo-geysers. 

The large Kuiper belt object (50 000) Quaoar reveals the presence of crystalline water ice and ammonia hydrate. Crystallinity indicates that the ice has been heated to at least 110 K. Both ammonia hydrate and crystalline water ice should be destroyed by energetic particle irradiation on a timescale of about 10 yr therefore Quaoar has been recently resurfaced, either by impact exposure of previously buried (shielded) ices or by cryovolcanic outgassing, or by a combination of these processes (Jewitt and Luu, 2004 [171]). 

CCls CHO. A colourless oily liquid with a pungent odour b.p. 98°C. Manut actured by the action of chlorine on ethanol it is also made by the chlorination of ethanal. When allowed to stand, it changes slowly to a white solid. Addition compounds are formed with water see chloral hydrate), ammonia, sodium hydrogen sulphite, alcohols, and some amines and amides. Oxidized by nitric acid to tri-chloroethanoic acid. Decomposed by alkalis to chloroform and a methanoate a convenient method of obtaining pure CHCI3. It is used for the manufacture of DDT. It is also used as a hypnotic. 

For this second reaction Kjgs = 181 x 10" and hence pK, for ammonia solution is 4.75. The entity NHj. H2O is often referred to as ammonium hydroxide, NH4OH, a formula which would imply that either nitrogen has a covalency of five, an impossible arrangement, or that NH4OH existed as the ions NH4 and OH". It is possible to crystallise two hydrates from concentrated ammonia solution but neither of these hydrates is ionic. Hence use of the term ammonium hydroxide is to be discouraged in favour of ammonia solution . 

The base strength of hydrazine is, however, lower than that of ammonia. As might be expected, hydrazine is readily soluble in water from which the hydrate N2H4.H2O can be crystallised. 

The solid readily dissolves chemically in concentrated hydrochloric acid, forming a complex, and in ammonia as the colourless, linear, complex cation [H3N -> Cu <- NHj] (cf AgCl) if air is absent (in the presence of air, this is oxidis to a blue ammino-copper(II) complex). This solution of ammoniacal copper(I) chloride is a good solvent or carbon monoxide, forming an addition compound CuCl. CO. H2O, and as such is used in gas analysis. On passing ethyne through the ammoniacal solution, a red-brown precipitate of hydrated copper(I) dicarbide (explosive when dry) is obtained ... 

Anhydrous cupric sulphate is white but forms a blue hydrate and a blue aqueous solution. The solution turns yellow when treated with concentrated hydrochloric acid, dark blue with ammonia, and gives a white precipitate and brown solution when treated with potassium iodide. A yellow-brown aqueous solution of ferric chloride becomes paler on acidification with sulphuric or nitric... 

The heat of hydration is approximately —70 kj /mol (—17 kcal/mol). This process usually produces no waste streams, but if the acrylonitrile feed contains other nitrile impurities, they will be converted to the corresponding amides. Another reaction that is prone to take place is the hydrolysis of acrylamide to acryhc acid and ammonia. However, this impurity can usually be kept at very low concentrations. American Cyanamid uses a similar process ia both the United States and Europe, which provides for their own needs and for sales to the merchant market. 

The reactor effluent, containing 1—2% hydrazine, ammonia, sodium chloride, and water, is preheated and sent to the ammonia recovery system, which consists of two columns. In the first column, ammonia goes overhead under pressure and recycles to the anhydrous ammonia storage tank. In the second column, some water and final traces of ammonia are removed overhead. The bottoms from this column, consisting of water, sodium chloride, and hydrazine, are sent to an evaporating crystallizer where sodium chloride (and the slight excess of sodium hydroxide) is removed from the system as a soHd. Vapors from the crystallizer flow to the hydrate column where water is removed overhead. The bottom stream from this column is close to the hydrazine—water azeotrope composition. Standard materials of constmction may be used for handling chlorine, caustic, and sodium hypochlorite. For all surfaces in contact with hydrazine, however, the preferred material of constmction is 304 L stainless steel. 

Iron(III) ammonium citrate [1185-57-5] is of indefinite stoichiometry. A brown hydrated compound [1332-98-5] of iron(III) ammonium citrate contains 16.5—18.5% iron, - 9% ammonia, and 65% citric acid. A green hydrated compound [1333-00-2] contains 14.5—16% iron, 1% ammonia, and 75% citric acid. Iron ammonium citrates are water soluble but are insoluble in alcohol. The compounds are used to fortify bread, milk, and other foods (see... 

Iron(III) bromide [10031-26-2], FeBr, is obtained by reaction of iron or inon(II) bromide with bromine at 170—200°C. The material is purified by sublimation ia a bromine atmosphere. The stmcture of inoa(III) bromide is analogous to that of inon(III) chloride. FeBr is less stable thermally than FeCl, as would be expected from the observation that Br is a stronger reductant than CF. Dissociation to inon(II) bromide and bromine is complete at ca 200°C. The hygroscopic, dark red, rhombic crystals of inon(III) bromide are readily soluble ia water, alcohol, ether, and acetic acid and are slightly soluble ia Hquid ammonia. Several hydrated species and a large number of adducts are known. Solutions of inon(III) bromide decompose to inon(II) bromide and bromine on boiling. Iron(III) bromide is used as a catalyst for the bromination of aromatic compounds. 

Evolution of ammonia from a boiling dilute solution of diammonium phosphate gradually reduces the pH. This process is used commercially to control the precipitation of alkaH-soluble—acid-insoluble coUoidal dyes on wool. Other ammonium orthophosphate salts of interest are ammonium hemiphosphate [28537-48-6] NH4H2PO4 H3PO4, and its hydrate [28037-74-3], as well as the trihydrate [78436-07-4] of DAP. 

Lauramide has been prepared by passing ammonia gas through lauric acid in the presence of metallic oxides, specifically a complex mixture of Si02—AI2O2—Fe202—CaO—SO in the ratio of 24 16 3 47 10. The oxides, which are hydrated during amidation, can be regenerated by calcination (12,13). 

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