Ammonia-based electrolytes

The hydrogen is principally used for the manufacture of ammonia-based fertilizers. With the advent of cheap natural gas as a source of hydrogen, however, the electrolytic route has largely become uncompetitive. Water electrolysis is also carried out to supply oxygen for life support in nuclear submarines that have the capability of remaining submerged for months at a time. This is a specialized application where there is no other option and therefore cost is immaterial. 

Lan and Tao [22] successfully applied a novel fuel cell type with an alkaline membrane to oxidize ammonia at room temperature. Compared to solid oxide fuel cells, the alkaline membrane fuel cell is less brittle and can be operated at low temperatures. As an advantage of alkaline membrane fuel cells over conventional alkaline fuel cells, no KOH-based electrolyte is needed. The researchers used two types of anodes first platinum and ruthenium deposited on carbon and sec-raid chromium-decorated nickel. The ammraiia sources were either ammraiia gas or a 35 wt% aqueous ammonia solution. 

As we have pointed out, strong acids and bases are completely ionized in water. As a result, compounds such as HC1 and NaOH are strong electrolytes like NaCl. In contrast, molecular weak acids and weak bases are poor conductors because their water solutions contain relatively few ions. Hydrofluoric acid and ammonia are commonly described as weak electrolytes. 

Weak acids with weak bases. The titration of a weak acid and a weak base can be readily carried out, and frequently it is preferable to employ this procedure rather than use a strong base. Curve (c) in Fig. 13.2 is the titration curve of 0.003 M acetic acid with 0.0973 M aqueous ammonia solution. The neutralisation curve up to the equivalence point is similar to that obtained with sodium hydroxide solution, since both sodium and ammonium acetates are strong electrolytes after the equivalence point an excess of aqueous ammonia solution has little effect upon the conductance, as its dissociation is depressed by the ammonium salt present in the solution. The advantages over the use of strong alkali are that the end point is easier to detect, and in dilute solution the influence of carbon dioxide may be neglected. 

Hexamethylenediamine (HMDA), a monomer for the synthesis of polyamide-6,6, is produced by catalytic hydrogenation of adiponitrile. Three processes, each based on a different reactant, produce the latter coimnercially. The original Du Pont process, still used in a few plants, starts with adipic acid made from cyclohexane adipic acid then reacts with ammonia to yield the dinitrile. This process has been replaced in many plants by the catalytic hydrocyanation of butadiene. A third route to adiponitrile is the electrolytic dimerization of acrylonitrile, the latter produced by the ammoxidation of propene. 

B—A (nitrous acid) and D (acetic acid) are weak acids, and E (ammonia) is a weak base. Weak acids and bases are weak electrolytes. C (ethanol) is a nonelectrolyte. Potassium nitrate (B) is a water-soluble ionic compound. 

Several computer-based techniques have been developed for more specific applications. Truesdell (45) describes a computer program for calculating equilibrium distributions in natural water systems, given concentrations and pH. Edwards, et al. (31, Z2) have developed computer programs for treating volatile weak electrolytes such as ammonia, carbon dioxide and hydrogen sulfide systems however, in their present state these programs (presumably) do not accommodate metallic species in solutions. 

Scheme 159) [549, 550]. Temperature and electrolyte concentration are found to have a profound effect on the reaction rate. The Bu4N(Hg) can be used for the reduction of -estradiol 3-methyl ether and the reaction has been shown to be more selective than the conversion methods based on alkali metal-ammonia reduction [551]. 

Simulated solar conversion efficiencies up to 6.8% on Ti substrates have been reported for annealed CD CdSe films in polysulphide electrolyte based on a low-ammonia-concentration-selenosulphate bath. Several successive depositions were required to build up an optimum final fihn thickness of 2.5 jim (when most of the hght was absorbed). The initial deposit was annealed to improve adherence and the final multideposited film was annealed at 550°C in air, followed by etching and zinc ion treatment. 

Electrical Conductance of Aqueous Solutions of Ammonia and Metal Hydroxides. Check the electrical conductance of 1 W solutions of sodium hydroxide, potassium hydroxide, and ammonia. Record the ammeter readings. Arrange the studied alkalies in a series according to their activity. Acquaint yourself with the degree of dissociation and the dissociation constants of acids and bases (see Appendix 1, Tables 9 and 10). Why is the term apparent degree of dissociation used to characterize the dissociation of strong electrolytes ... 

Electronic Time Fuze. Development of an electronic time fuze which would be substantially more accurate than exisitng time fuzes is described in the report of Texas Instruments, Inc (Ref). A programmable digital circuit is driven by. an oscillator based on a Picatinny Arsenal design. As power source, two types of battery, a silver-zinc primary battery and a reserve battery which uses ammonia as the electrolyte, were tried. A detailed manufacturing plan is included as an appendix... 

It is interesting to note37 an early process which was based on ammonia/ammonium chloride in which the electrolyte contained the tetraammine [Zn(NH3)4]2+. This solution never found general acceptance, although it has been used for wire plating. 

Bases, like acids, can also be either strong or weak, depending on the extent to which they dissociate and produce OH- ions in aqueous solution. Most metal hydroxides, such as NaOH and Ba(OH)2, are strong electrolytes and strong bases, but ammonia (NH3) is a weak electrolyte and a weak base. Ammonia is weakly basic because it reacts to a small extent with water to yield NH4+ and OH- ions. In fact, aqueous solutions of ammonia are often called "ammonium hydroxide," although this is really a misnomer since the concentrations of NH4+ and OH ions are low. 

E. C. Szarvasky found that the electrolysis of hydroxylamine was accompanied by the spontaneous transformation of hydroxylamine into ammonia. Secondary reactions always occur—the base being reduced to ammonia at the cathode and at the anode oxidized to nitrogen oxides. F. Balia found that with various electrodes the percentage current yield of NaN02 NaN03 in the electrolytic oxidation of hydroxylamine with anodes of different metals was as follows ... 

Semicarbazide (Aminourea, Carbamylhydrazine or Hydrazine carboxamide). NHi.NH.CO.NHj mw 75.07 colorl prisms mp 96° d l,484g/cc at 4°. V sol in w sol in ethanol. Prepn is by electrolytic redn of nitrourea in sulfuric acid. The base Is then obtd by reaction of the semicarbazide sulfate with liq ammonia. CA Registry No [57-56-7]. See also in Vol 2, C45-L, under Carbazide for a definition of semicarbazide Semicarbazide forms salts which are either expl or, as in the case of the hydrochloride, are used in propint compns... 

The interpretation of the kinetic salt effect in aqueous solutions is based on the theory of strong electrolytes, but the latter can only be applied to ammonia solutions of uni-univalent salts at concentrations lower by a factor of 106 than the concentrations employed in the above experiments (Pleskov, 1937). It follows that the existing quantitative theory cannot be used to interpret the results obtained. 

Arrhenius acid-base theory - Arrhenius developed the theory of the electrolytic dissociation (1883-1887). According to him, an acid is a substance which delivers hydrogen ions to the solution. A base is a substance which delivers hydroxide ions to the solution. Accordingly, the neutralization reaction of an acid with a base is the formation of water and a salt. It is a so-called symmetrical definition because both, acids and bases must fulfill a constitutional criterion (presence of hydrogen or hydroxide) and a functional criterion (to deliver hydrogen ions or hydroxide ions). The theory could explain all of the known acids at that time and most of the bases, however, it could not explain the alkaline properties of substances like ammonia and it did not include the role of the solvent. -> Sorensen (1909) introduced the -> pH concept. 

One key property of a solution is its electrical conductivity or ability to conduct electricity. When a substance, a solute, is dissolved is water, a solvent, ions may or may not be formed. A strong electrolyte is formed when the solute completely ionizes (the substance completely separates into ions), such as sodium chloride (a soluble salt), hydrochloric acid (strong acid), or sodium hydroxide (strong base). A weak electrolyte is formed when the solute partially ionizes, such as acetic acid (weak acid) or ammonia (weak base). A nonelectrolyte is a substance that dissolves in water but does not ionize, such as sugar or alcohol. Most soluble, nonacid organic molecules are nonelectrolytes. 

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