Lead nitrate, decomposition

The comparison with the TPD data showed that the presence of hydrogen did not affect significantly the temperature threshold for nitrate decomposition, but leads to a different product distribution. As suggested by Cant and Patterson [42], the observed product distribution can be ascribed to the occurrence of the following reactions ... 

Dining evaporation of an alkaline aqueous solution of the nitrate, decomposition led to gas evolution and a pressure explosion occurred. This was attributed to the use of recovered alkali containing high levels of lead and iron, which were found to catalyse the thermal decomposition of the nitrate. Precautions to prevent recurrence are detailed. 

According to an O.S. amendment sheet, the procedure as described [1] is dangerous because the reaction mixture (dicyanodiamide and ammonium nitrate) is similar in composition to commercial blasting explosives. This probably also applies to similar earlier preparations [2]. An earlier procedure which involved heating ammonium thiocyanate, lead nitrate and ammonia demolished a 50 bar autoclave [3], TGA and DTA studies show that air is not involved in the thermal decomposition [4], Explosive properties of the nitrate are detailed [5], An improved process involves catalytic conversion at 90-200°C of a molten mixture of urea and ammonium nitrate to give 92% conversion (on urea) of guanidinium nitrate, recovered by crystallisation. Hazards of alternative processes are listed [6],... 

Spent acid from nitroglycerine manufacture is not used to prepare nitrating mixture since it contains too much organic matter with which it is undesirable to contaminate the nitration. Decomposition of these substances during nitration could make the process difficult to control and might lead to accidents. 

About ten grams of lead iodide are prepared by double decomposition from the requisite amounts of lead nitrate and potassium iodide (in slight excess) in a total of 200ml of water, filtered, and dried in the oven at 100°C. 

The early workers on phosphorus prepared that element from urine which normally contains ammonium and sodium phosphates. Thus, R. Boyle1 evaporated the urine to a syrupy consistency, and distilled the product either alone or admixed with sand or charcoal. The carbon produced by the decomposition of the organic matter in the urine, or added to it in the form of charcoal, decomposes the ammonium phosphate, without affecting the sodium phosphate. A. S. Marggraf mixed the cone, urine with lead chloride and charcoal powder, and heated the mass until it became pulverulent. The ammonium and sodium phosphates were converted into lead phosphate, and on distillation, the carbon liberated the phosphorus from the lead phosphate. G. A. Giobert mixed the unevaporated urine with lead nitrate or acetate washed the precipitated mixture of lead phosphate and sulphate mixed the precipitate with charcoal and distilled the dried product. 

The characteristic colours and solubilities of many metallic sulphides have already been discussed in connection with the reactions of the cations in Chapter III. The sulphides of iron, manganese, zinc, and the alkali metals are decomposed by dilute hydrochloric acid with the evolution of hydrogen sulphide those of lead, cadmium, nickel, cobalt, antimony, and tin(IV) require concentrated hydrochloric acid for decomposition others, such as mercury(II) sulphide, are insoluble in concentrated hydrochloric acid, but dissolve in aqua regia with the separation of sulphur. The presence of sulphide in insoluble sulphides may be detected by reduction with nascent hydrogen (derived from zinc or tin and hydrochloric acid) to the metal and hydrogen sulphide, the latter being identified with lead acetate paper (see reaction 1 below). An alternative method is to fuse the sulphide with anhydrous sodium carbonate, extract the mass with water, and to treat the filtered solution with freshly prepared sodium nitroprusside solution, when a purple colour will be obtained the sodium carbonate solution may also be treated with lead nitrate solution when black lead sulphide is precipitated. 

Ferrous nitrate may also be obtained in solution by grinding lead nitrate with an equivalent quantity of ferrous sulphate in the presence of dilute alcohol, double decomposition takes place, the ferrous nitrate passing into solution. Upon evaporation at room temperature the salt... 

Lead ferricyanide, Pb3[Fe(CN)6]2.16H20, is obtained by double decomposition of lead nitrate with potassium ferricyanide. It yields dark reddish brown crystals. 

Lead Metatungstate, PbW Ojg.SHjO, is obtained as a white flocculent precipitate by double decomposition. It is insoluble in water soluble in hot nitric acid. However, by the addition of lead nitrate to an alkali tungstate solution, a crystalline precipitate has been obtained, of composition PbWjOi3.Pb(NO3)2.10H3O. This is only very slightly soluble in water, and when heated it loses THgO. 

A very simple and gentle oxidation of primary alcohols to aldehydes is their treatment in chloroform or carbon tetrachloride with a solution of dinitrogen tetroxide, obtained either commercially or by thermal decomposition of lead nitrate. The reaction is carried out at 0 °C through room temperature and gives high yields (91-98%) of benzaldehydes (equation 206) [454]. 

Several hydrated transition metal nitrates (Co, Cu, Cr, Zn and Ni) undergo aqueous fusion [62] prior to hydrolysis which yields basic salts. Vratny and Gugliotta [63] reported sigmoid -time curves for the decomposition of Pb(N03)2 between 523 and 708 K, and concluded that the cation was not further oxidized. Margulis et al. [64] identified both dissociation and autoxidation steps during the decomposition of lead nitrate. The first step involved melting of the eutectic formed from the reactant and the initial product, 2Pb0.Pb(N03)2. 

As mentioned above, this substance is more stable in long-term storage than are the oxides of alkali metals. Reference data show that heating pure Na202 to temperatures above 460 °C results in its decomposition to sodium oxide [114, 121]. Dissolution of Na202 in molten salts leads to decomposition at appreciably lower temperatures. Nevertheless, in molten nitrates possessing... 

Adadurov41 prepared catalysts by adsorbing lead nitrate on carbon, then drying, and heating to 360° C. He found that when these catalysts were employed for the decomposition of formic acid, the course of the reaction depended on the conditions under which the lead nitrate had been originally adsorbed. Formic acid was decomposed into carbon dioxide and hydrogen when the catalyst was prepared by adsorbing the lead salt from an 0.01 N solution whereas appreciable amounts of carbon monoxide were formed with a catalyst prepared with a 0.05 N solution of lead nitrate. 

Fig. 2.4 Mass intensity signals of Pb species for the thermal decomposition of a lead nitrate sample containing 0.4 pg Pb (a) PbO and (b) Pb . The experimental conditions are indicated in Table 2.1. (Reprinted from [11], with permission.)...

In the course of low-temperature decomposition of the nitrates, approximately half of the low-volatility product (Ag or CdO) condenses on the platform surface. This is confirmed, in particular, by the fact that the sum of the intensities of low-temperature peaks of CdO, CdNO, and Cd in decomposition of Cd(N03)2 is close to the intensity of the high-temperature peak of Cd in the decomposition of CdO (Fig. 16.3). A similar conclusion was reached for the decompositions of nickel and lead nitrates (Figs. 2.3 and 2.4). 

Attempts to isolate trifluoroacetyl nitrate by distillation lead to decomposition. Acetyl nitrate is known to give high ratios of ortho-nitrated products [14]. Similar trends in orientation are seen in the product distributions obtain in TFAA-NH4NO3 nitrations. However, in contrast to the rather limited range of substrates that can be nitrated with acetyl niuate, trifluoroacetyl nitrate is a much more efficient and versatile nitrating agent. 

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