Transition of ammonium nitrate

Yamazoe, Microscopic Observation of Phase Transitions of Ammonium Nitrate , JCrystal-Growth 2, 255-66 (1968) 30) R.D. Rich,... 

Seiyama, The Dielectric Properties of and Phase Transitions in Ammonium Nitrate , KogyoKagakuZasshi 71 (11), 1821-27 (1963)... 

The pf-relations of the six different forms of ammonium nitrate are illustrated diagrammatically in Eig. 85. M. Bellati and R. Romanese, and U. Behn measured the changes in volume at atm. press, at the four transition points. M. Bellati and R. Romanese have also measured the latent heats of the transformation... 

The ease of detonation of ammonium nitrate is greatly influenced by its density. This was studied in detail by Fukuyama [36]. He prepared porous ammonium nitrate. The porous state appears at the transition points of 125 and 84°C when cooled. After the transition, the salt reserves its normal, less porous state. By rapid cooling the porous state can be preserved. 

It is remarkable how particular systems attain the status of classics . Hartley (1902) noted a and ft sulphur (transition temperature 95.6 °C), red and yellow mercuric iodide (transition temperature 126 °C) (Hostettler et al. 2001) and the four modifications of ammonium nitrate as examples of enantiotropic behaviour. These three systems are given as archetypical experiments in Chamot and Mason s book (1973) on chemical microscopy. 

V. Rothmund showed that in the general case of solid soln., the effect of a solute on the transition temp, of the solvent is analogous to the cryoscopic effect of a liquid soln., and the depression of the transition temp, is given by Oq—Oi =RT IQ(C2 Ci), where 6q and 61 denote the transition temp, of ammonium nitrate before and after the addition of potassium nitrate T, the absolute transition, temp, of ammonium nitrate alone Cq and Oi, the mol, cone, of potassium nitrate in 100 grms. of the two modifications of ammonium nitrate, and Q is the heat of transformation of ammonium nitrate. The results with potassium and ammonium nitrates are in accord with V. Rothmund s rule, and, at 32°, there is a change of quadruple into triple molecules 3(NH4N03)4= 4(NH4N03)3. 

On the other hand, the passage of the j8-rhombic into the rhombo-hedral form of ammonium nitrate is accompanied by a contraction, and the transition point is therefore lowered by increase of pressure, as shown by the following numbers — ... 

A disadvantage of ammonium nitrate is its hygroscopicity and a crystal-structure change that increases its volume by 3.8 % at the unfortunate transition temperature of 32 C, which is also the popular summer temperature of 90 F over most of the United States. This transition point can be shifted, i.e. depressed by about 20 , but not abolished, by admixture of 8% of potassium nitrate. 

The transitions from forms II to III and IV to V result in volume increases the changes from I to II and III to IV are accompanied by a decrease in volume. These volume changes frequently cause difficulty in the processing and storage of ammonium nitrate. The salt can readily burst a metal container into which it has been cast when change II to III occurs. The drying of ammonium nitrate crystals must be carried out within fixed temperature limits, e.g. 40-80 °C,... 

Davey, R.J., Guy, P.D. and Ruddick, A.J. (1985) The IV-III pol5unorphic phase transition in aqueous slurries of ammonium nitrate. Journal of Colloid and Interface Sciences, 108, 189-192. 

Herrmarm MJ, Engle W (1997) Phase transitions and lattice dynamics of ammonium nitrate. Propopellants, Explosives, and Pyrotechnics 22 143-147. 

However, if transition metal exchanged zeolites are active materials in NH3-SCR, N2O emission can be also observed. N2O emission constitutes one of the main drawbacks of this system. For instance, Wilken et al. [112] reports a maximum N2O production at 200 °C over Cu-Beta zeolite. Mechanism of N2O emission is proposed to proceed through the decomposition of ammonium nitrates (reaction 19.28) ... 

Sohd ammonium nitrate occurs in five different crystalline forms (19) (Table 6) detectable by time—temperature cooling curves. Because all phase changes involve either shrinkage or expansion of the crystals, there can be a considerable effect on the physical condition of the sohd material. This is particularly tme of the 32.3°C transition point which is so close to normal storage temperature during hot weather. 

Ammonium Nitrate Plant 7. Prill lower reduce microprill formation and reduce carryover of fines through entrainment. 8. Materials handling where feasible use covers and hoods on conveyors and transition points. Good cleanup practices must be in place to minimize contamination of stormwater mnoff from the plant property. 9. Granulators reduce dust emissions from the disintegration of granules. 

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