Nitrogen ammonia preservation

Analysis of meat extract has the same objects as that of fresh meat or sausages, namely, to determine the composition and nutrient value of the extracts and to detect adulterations and preservatives. With extracts of the Liebig type, determinations should always be made of the water, ash, potassium, fat and total nitrogen, while tests should be made for nitre and preservatives. Further, it is always useful to determine the various forms of combination of the nitrogen, especially the creatinine and the ammonia see 7, 8 and 9, below). In mixed extracts, besides determinations of the... 

Ammonia is found in the environment as the result of natural and industrial processes. It is released into the environment by the breakdown of organic wastes, and it is a constituent of the soil, the atmosphere, and bodies of water. Ammonia is also a key intermediate in the nitrogen cycle and is a product of amino acid metabolism (WHO 1986). Anhydrous ammonia is used in the production of nitric acid, explosives, synthetic fibers, and fertilizers (Budavari 1989). It is used as a refrigerant as a corrosion inhibitor in the purification of water supplies in steel production as a catalyst for polymers as a preservative for latex and in the production of nitrocellulose, urea formaldehyde, sulfite cooking liquors, and nitroparaffins (ACGIH 1991 Lewis 1993). Ammonium hydroxide (10-35% ammonia) is a major constituent of many cleaning solutions. Ammonia... 

Secondary amines give only a monosubstituted product. Both of these reactions are thermally reversible. The product with ammonia (3,3, 3"-nitrilotrispropionamide [2664-61-1] C9HlgN403) (5) is frequently found in crystalline acrylamide as a minor impurity and affects the free-radical polymerization. An extensive study (8) has determined the structural requirements of the amines to form thermally reversible products. Unsymmetrical dialkyl hydrazines add through the unsubstituted nitrogen in basic medium and through the substituted nitrogen in acidic medium (9)). AlonoalkyHiydroxylamine hydrochlorides react with preservation of the hydroxylamine structure (10). Primary nitramines combine in such a way as to keep the nitramine structure intact. 

USE In manuf of ammonia, nitric acid, nitrates, cyanides, etc. in manuf explosives in filling high-temp thermometers, incandescent bulbs to form an inert atm for preservation of materials, for use in dry boxes or glove bags. Liquid nitrogen in food-freezing processes iu the laboratory as a coolant. Pharmaceutic aid (air displacement). Caution In high concns it is a simple asphyxiant. 

Nitrided zeolites were prepared by thermal treatment of ultrastable zeolite Y (Si/Al ratio equal to 13) under ammonia flow for a prolonged time. The effects of the nitridation parameters on the extent of the nitrogen incorporation and on the structural and catalytic properties of the resulting zeolites were investigated. The amount of nitrogen incorporated in the zeolite increases with temperature and duration. Structural order and porous volume are preserved if the nitridation temperature and the nitridation time do not exceed 800°C and 72 h, respectively. Nitrided zeolites are base catalysts as revealed by the reaction of Knoevenagel condensation between benzaldehyde and malononitrile. 

There are other such examples. Many unsaturated soils are known to convert to N2(g> via NO3 (i.e., nitrification then denitrification). They achieve this because there are local oxic and anoxic environments in the soil waters that, respectively, allow nitrification and denitrification to proceed. In stratified lakes, nitrification may occur in the oxygenated epilimnion (upper layer) and denitrification in the hypolimnion (bottom water) and in the sediment pore water where dissolved oxygen concentrations fall to zero. The nitrification and denitrification process is important in preserving the fishery in Indian Creek Reservoir in the Sierra Nevada mountains. This reservoir is fed by the tertiary effluent from the City of South Lake Tahoe sewage treatment plant. The effluent has at times contained 15 to 20 mg NH4 N/liter. Levels of ammonia of this magnitude are toxic to fish, yet in the reservoir there is a thriving fishery. This is achieved because the top waters of the lake nitrify the ammonia to nitrate and this is reduced to N2(g) by the anoxic bottom waters. The summer concentrations of nitrogen species of the reservoir are approximately 4 mg NOa -N/Iiter and 4 mg NH4-N/liter. 

As the pressure increases, higher temperatures are needed to preserve high conversion efficiency. The temperature is controDed by preheating the air and ammonia and by the amount of excess air. However, the theoretical temperature limit is about 1000°C, above which the decomposition of ammonia to nitrogen starts to predominate. Ammonia conversion efficiency as a function of temperature and pressure is given in Table 8.7. 

This result was confirmed with other substances and showed in evidence that unstable free radicals by irradiation generated at liquid nitrogen temperature could be preserved and stabilized at room temperature by freeze-drying of their solution in ammonia at very low temperatures. This, of course, would be strictly impossible in a water solution. 

Neither of these two preservatives can be recommended here. With the exception of silicate (see Section 2.2.3.2), adding sulphuric acid may be even worse than no treatment. This is particularly true for the preservation of nitrogen compounds. At low pH, nitrite can be lost rather rapidly as a result of its oxidation to nitrate or because of its reaction with ammonia or a-amino acids. The unsuitability of this preservative for the storage of dissolved phosphate has already been outlined in Section 2.2.3.2. 

Sulfur dioxide or bisulfites are rarely used in combination with nitrites, because their reactions in acidic media yield sulfonates of either hydroxylamine or ammonia, which destroys the preservative activity of the individual additives. The reaction of alkali metal nitrites with bisulfite at lower temperatures leads to the formation of hydroxylamine N, JV-disulfonate, H0N(S03)2, which is hydrolysed to hydroxylamine JV-sulfonate, HONHSOj and further to hydroxylamine (H2NOH). At elevated temperatures complete substitution proceeds with the formation of ammonia JV-trisulfonate, N(S03)j , which is hydrolysed to sulfa-mate, H2NSOj . Subsequent reaction of sulfamate with nitrous acid leads to production of bisulfate ion and nitrogen gas ... 

---