Ammonia/ammonium references

Nitrogen NMR data have been obtained using both the low-abundance, spin = 1/2 N and the predominant spin = 1 N nuclei. Several different references have been used for nitrogen NMR including aqueous ammonia, ammonium salts, acetonitrile, nitric acid, and nitrates. Current opinion favors neat nitromethane, and the compilation of the known data for 1,4-oxazines (Table 6) is expressed with respect to this reference and arranged in order of the observed chemical shift. For the C-labeled compound 87, carbamate rotamers lead to two separate signals and the value of 7c n can be determined -283.98 (d, J 9) and -284.46 (d, 7 11) <2001JOC8010>. 

For the outline of a direct method of preparation from ammonium dichromate and hydrochloric acid, followed by ammonia, see reference 2. 

In discussing the concentration of ammonia monitored in the environment, it is important to consider both ammonia and its conjugate acid, the ammonium ion. Independent determination of these compounds cannot always be achieved. In an analysis of the literature, it is difficult to separate aqueous ammonia concentration from aqueous ammonia-ammonium concentrations unless the investigators made a special effort to determine the amount of un-ionized ammonia. In this section of the document, ammonia will refer to the ammonia and ammonium concentration, and un-ionized ammonia will refer specifically to the ammonia concentration. 

The test identifies the substance to be examined as either a salt of anunonium, NH4+, or as the salt of a volatile (nitrogen) base. At the present only two monographs give reference to ammonium salts and salts of volatile bases. One monograph describes a distillate of bituminous schists (black slate) containing both lower amines and inorganic ammonia. The other is a tertiary amine, which upon hydrolysis yields ammonia. Ammonium is almost identical in size to potassium and therefore has properties that are almost identical to this. Like the alkali metals it forms water-soluble salts with all but a few inorganic anions. A precipitation therefore is not the obvious choice for a method of identification, and consequently the test is based on ammonia s most obvious difference from the alkali metals, its volatility. 

FIGURE 6.18 The formation of a coordinate covaient bond, (a) When hydrogen ions are in a soiution together with ammonia moiecuies, the hydrogen ion moves in to share the open pair of eiectrons on the ammonia moiecuie (refer back to Figure 6.10). (b) The compiete Lewis structure of the ammonium ion. 

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 . 

Note. All values are with reference to the molarity scale. Data for bases are expressed as acidic ionisation constants e.g. for ammonia we quote pK at =9 245 for the ammonium ion... 

Widespread medicinal use of colloidal bismuth subcitrate (CBS) has prompted extensive studies of bismuth compounds involving the citrate anion. Bismuth citrate is essentially insoluble in water, but a dramatic increase in solubility with increasing pH has been exploited as a bio-ready source of soluble bismuth, a material referred to as CBS. Formulation of these solutions is complicated by the variability of the bismuth anion stoichiometry, the presence of potassium and/ or ammonium cations, the susceptibility of bismuth to oxygenation to Bi=0, and the incorporation of water in isolated solids. Consequently, a variety of formulas are classified in the literature as CBS. Solids isolated from various, often ill-defined combinations of bismuth citrate, citric acid, potassium hydroxide, or ammonium hydroxide have been assigned formulas on the basis of elemental analysis data or by determination of water and ammonia content, but are of low significance in the absence of complementary data other than thermal analysis (163), infrared spectroscopy (163), or NMR spectroscopy (164). In this context, the Merck index lists the chemical formula of CBS as KgfNHJaBieOafOHMCeHsCbh in the 11th edition (165), but in the most recent edition provides a less precise name, tripotassium dicitrato bismuthate (166). 

Acid hydrolysis of an amide yields a carboxylic acid and an ammonium ion. The mechanism for acid hydrolysis is shown in Figure 12-36. Base hydrolysis of an amide, on the other hand, yields ammonia and a carboxylate ion. You can see this mechanism in Figure 12-37. To identify similarities, compare these mechanisms to the mechanisms for the hydrolysis of esters (refer to Figures 12-34 and 12-35). 

Figure 4.15 — (A) Tubular flow-through electrode 1 Perspex body 2 conducting epoxy cylinder 3 mobile carrier PVC membrane 4 electric cable 5 channel (1.2 mm ID) 6 holders 7 screws 8 0-rings. (B) Schematic diagram of a system for on-line monitoring of ammonia ISE tubular flow-through ammonium ion-selective electrode R reference electrode W waste. (Reproduced from [137] with permission of the Royal Society of Chemistry).

The single largest use of ammonia is its direct apphcation as fertdizer, and in the manufacture of ammonium fertilizers that have increased world food production dramatically. Such ammonia-based fertilizers are now the primary source of nitrogen in farm soils. Ammonia also is used in the manufacture of nitric acid, synthetic fibers, plastics, explosives and miscellaneous ammonium salts. Liquid ammonia is used as a solvent for many inorganic reactions in non-aqueous phase. Other apphcations include synthesis of amines and imines as a fluid for supercritical fluid extraction and chromatography and as a reference standard in i N-NMR. 

As mentioned before, the sensory properties of the various heterocyclic compounds discussed in this contribution are one of the important factors determining food quality. The data on sensory characteristics of the various numerous compounds formed through the reaction of aldehydes with ammonia or ammonium sulfide, in the presence or in the absence of acetoin, are scattered in the literature (57) and thus are not easy to find. At the same time, information on sensory characteristics of compounds of this type is of primary importance to food chemists. Sultan (29) has compiled much of this information which is presented here in Table IV where also the appropriate references to the original literature are given. 

A point concerning CdS deposition. Many studies have used what is referred here to as the standard deposition bath. This bath is made up of a Cd salt, ammonia (sometimes with an ammonium salt to lower the pH) to complex the Cd and adjust the pH, thiourea, and deposition temperatures usually in the range of 60-90°C. Of course, this bath still allows for large differences in reactant concentrations (e.g., the Cd concentration varies from a low of 1 mM to as much as 100... 

Erdmann,1 in 1866, prepared the first member of this series, namely, ammonium tetranitrito-diammino-cobaltate, [Co(NH3)2(N02)4] NH4. The salt is sometimes referred to as Erdmann s salt on that account. Later, Gibbs prepared other salts of the same type, and showed that in these salts the cobalt atom, united with ammonia and acidic radicles, forms a negative radicle.2 Werner then showed that these salts form the connecting link between the neutral un-ionised complex triacido-triammino-eobalt compounds and the double salt, such as potassium eobalti-nitrite. Thus, by replacement of ammonia molecules by acid radicles a transition takes place from trinitrito-triammino - cobalt to potassium tetranitrito - diammino - cobaltate, [Co(NH3)2(N02)4]K, then to potassium pentamtrito-ammino-eobalfate. [Co(NH3)(N02)5]K, and finally to hexanitrito-cobaltate, [Co(N02)e]Iv3. Tetra-acido-diammino-cobaltates are therefore the salts of the acid tetra-acido-diammino-cobaltic acid, [Co(NH3)2R4]H. 

Tests for mordants. The principal mordants may be detected by the method indicated on p. 473 for their detection in dyed woollen goods. As mordants for cotton goods use is made also of antimony salts and sometimes of nickel salts. If the method referred to is followed, antimony will be identified as sulphide when the hydrochloric acid solution of the disaggregated mass is treated with hydrogen sulphide nickel will be identified as sulphide, separated by the action of ammonium sulphide on the filtrate obtained after the treatment with ammonium chloride and ammonia. 

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