Thallous azide

The reliable generation of deton press under 100 kilobars should offer advantages from an engineering viewpoint in applications where higher pressures are neither needed nor desired. Certain plastic/expl formulations described (Ref 1) offer these advantages in addition to others, such as the capability of being extruded or injection molded into difficult configurations and then polymerized in place. Expls included superfine PETN, acetone fine RDX, dextrinated LA and Thallous Azide... 

The properties of thallous azide have been examined in detail by Gray and Waddington [120]. 

Thallous azide is a yellow, crystalline substance, m.p. 334°C. The crystal structure as determined by X-ray analysis points to the isomorphism of T1N3 with KN3 and RbN3 azides. 

Thallous azide is sensitive to the action of light and decomposes under its influence to evolve metallic thallium. 

Deb and Yoffe [134] examined the decomposition of thallous azide under the action of ultra-violet light in the wavelength region 3200-3800 A. Two exciton bands 3415 and 3348 A have been observed in thallous azide by low-temperature spectroscopy (Nikitine and Gross s method). The refractive index has been measured by the Brewster angle method, the electron energy levels have been estimated and the results of the photochemical decomposition have been related to the electron energy level and to measurement of photoconductivity [33],... 

The DTA thermograms indicate for each type a shifting downwards of the exotherm at the 1.0 x 10SK level. The IR spectra for the various Pb azides reveal that a form of Pb carbonate is evident at the higher exposure. This is probably the reason for the lower values in the vacuum stability test listed is Table 11. Another interesting feature was the formation of ammonium nitrate on top of each Pb azide and thallous azide irradiation capsule (as shown in Fig 16) subjected to over 109R... 

The thallous azide was subjected to an exposure. 5,4 x 109 R and was reduced to a form of thallous oxide according to IR spectra... 

The more recent expts involving UV and X-ray irradiations were performed by Wiegand (Ref 226) who determined the changes in the optical properties of Pb and thallous azides. The same type of extinction due to colloidal metal was caused by both types of radiation and is increased in magnitude with decreasing wavelength to the band edge... 

The heavy metal pseudohtilides fall in this group since covalent forces are partially present. The structural parameters listed in Table 4 show that thallous azide, fulminate and cycmate are isostructural with the tetragonal alkali metal salts, while thallous thiocyanate is isostructural with the room temperature phase of potassium thiocyanate. The lattice constants of the salts axe all indicative of abnormally short metal-anion distances. The silver salts form an interesting series where the subtle interactions which result as a function of the electron affinity, electronic structure and size of the anions, stimulate somewhat predictable variations of crystal geometry. Silver azide is an example of a distortion of the tetragonal D4 (Fig. 1) lattice due to covalent metal-emion interaction which lowers the space symmetry of the crystal to D2 (29), while silver thiocyanate is mainly covalent with bidentate metal-anion chains... 

In sodium azide a transition occurs at 19 °C (9) and also on application of 1 kbar pressure 37a), in which the rhombohedral lattice transforms by a shearing motion of the azide ion layers to form a monoclinic unit ceU (9). The latter is isostructural with the unit cell of lithium azide shown in Fig. 2 b. Among the tetragonal rubidium, cesium and thallous azides a high temperature transformation in the range 151 °C to 315 °C to a cubic structure takes place (77), while at —40 °C a transition to an orthorhombic structure has been recently established for thallous azide 38). In the range 4 to 6 kbar, Pistorius 39) has observed pressure induced polymorphs of rubidium, cesium and thallous azides which are expected to be isostructural with the low temperature phase in thallous azide. 

The symmetry allowed modes at ft 0 have been determined using infrared and Raman spectroscopic techniques by Iqbal el al for a number of alkali pseudohalides 19, 41, 54,55), and ammonium 56), barium 26), a-lead 57) and thallous azide 45). The A 0 dependence of the first... 

The static dielectric constant (eo) of the alkali azides (cf. Table 11) is of the order of 6.5 while is 2.3. These values are of the same order as those of the alkali halides. Both the high and low frequency dielectric constants increase in the case of thallous. silver and cuprous azides. This is likely to be due to the increasing polarizibihty of the cations and a reflection of the decreasing ionicity of the lattices. The eo value for thallous azide and silver fulminate are however surprisingly high compared with the other azides. 

Ni and CNO can exist in a metastable state in ionic lattices. Among the azides, the anion is essentially unperturbed in the alkali metal salts but in the more complex heavy metal salts increasing perturbation of the anion occurs which is reflected in the asymmetric intraionic distances of the divalent salts in particular. This may be one of the reasons why the heavy metal salts are unstable with respect to the alkali metal azides. It is therefore pertinent to note that among the divalent azides the thermal sensitivity increases with the increasing asymmetry of the azide ions which increases in the order BaNe < PbNe < CuNe (c/. Table 2). Electron microscopic observations on thallous azide crystals have shown that the cubic form of the salt is relatively stable compared with the low temperature orthorhombic form (85). This is probably associated with the existence of asymmetric azide ions in the latter poljmiorph (c/.) Section IID). 

Colloidal Special purpose (RD1333) Dextrinated Barium azide Thallous azide... 

After many years of laboratory experience with various azides, the authors can report no occurrence of poisoning symptoms attributable directly to solid azides. However, with substances such as thallous azide, the physiological effects of thallium, in addition to the azide toxicity, are of equal concern. 

The effect of temperature on the impact sensitivity of thallous azide is shown in Figure 11. At - 100°C a decrease was obtained when tested with the Picatinny Arsenal apparatus. The results at room temperature indicate that... 

Lead azide and thallous azide were subjected to long exposures of Co... 

An approach which circumvents the problem of the effect of particle-size distribution on decomposition kinetics was adopted by Walker et al [26] and by Fox [10], who worked with individual single crystals or collections of noninteracting particles of uniform size. A typical lead azide preparation of the latter type is shown in Figure 4. Walker et al found that sodium and thallous azides do indeed show induction periods which are dependent upon particle size the... 

Figure 9. Arrangement of thallium ions in thallous azide. Dotted outline shows the unit cell, and the full line indicates the geometry of the pyramidal crystals which commonly form from solution. The arrow indicates the direction in which decomposition takes place.

Figure 10. Projection onto the (001) plane of the thallous azide structure. The azide ions are at 0,1/2,1, and lie in the plane.

Figure 14. The slow thermal decomposition of thallous azide. The insert shows the change in composition of the gas phase as decomposition proceeds [82].

Often in research unforeseen applications emerge which were not apparent beforehand. Studies of the decomposition processes in the azides have led to such bonuses. For example, radiation-induced decomposition of thallous azide produces colloidal disorder efficiently at low temperatures. Thus, this material could be used in a low-temperature photographic process [7-9]. 

---