Lead sulfate, decomposition

Lead compounds are generally added to polyvinyl chloride in electrical formulations in order to stabilize them against thermal decomposition 7 p.h.r. of National Lead Tribase XL modified tribasic lead sulfate was used throughout the present study. Since the stabilizer itself is an ionic impurity, it is remarkable to note that it actually increases volume resistivity (Table IV). 

Prolonged contact of the material with sulfuric add causes decomposition to lead sulfate and chlorine. The compound dissolves without decomposition in dry chloroform and carbon tetrachloride, and also in concentrated hydrochloric add. 

The retention of sulfur is also influenced to a large degree by the lead level in the fuel that is related to the mentioned tendency to form lead sulfates and oxysulfates. Decomposition, especially that on catalysts... 

Lead Sulfate—PbSO<—303.9—is formed by the action of hot, concentrated HaS04 on Pb or by double decomposition between a sulfate and a Pb salt in solution. It is a white powder, almost insoluble in HaO, soluble in concentrated HaS04, from which it is deposited by dilution. 

For instance, magnesium sulfate has a more marked effect than other sulfates because it also leads to decomposition of the hydrated calcium silicates. Ammonium sulfate is especially aggressive, because the ammonia produced escapes as a gas. 

Many lead sinter plants incorporate secondary materials such as lead residues containing lead sulfate in their charge. The decomposition of sulfate is endothermic and can significantly affect peak bed temperature and the quality of the sinter produced. Consequently, there are limits to the amount of... 

Depending on the smelting process used there can be limits to the acceptable proportion of feed represented by such residues. For the sinter plant-blast furnace combination the input of sulfate residues is commonly limited to around 25 per cent of net new feed. The decomposition of lead sulfate is endothermic and can limit the attainment of peak bed temperatures in the sinter plant, affecting the quality of sinter produced, which is critical to blast furnace performance. This is discussed in detail in Chapter 4. Many of the direct smelting processes covered in Chapter 7 are more able to cope with residue feeds, particularly the Kivcet and Kaldo processes. 

Aqueous solutions of chloric and bromic acids are formed by disproportionation of CI2 or Br2 in hot alkaline solution [Eq. (15) and (16)] or by treating the appropriate barium halate salt with sulfuric acid and removing the precipitated barium sulfate [similar to Eq. (41)]. Concentration of these solutions leads to decomposition of the acid. 

The model catalyst surface was covered with sulfur by adsorbing H2S at -143°C, followed by heating to 427°C, which leads to decomposition of the H2S. Oxygen was dosed by means of a molecular beam to obtain high local pressure at the sample. The measurements at the stepped Pt(335) surface were compared with the results obtained for a flat Pt(lll) surface under similar conditions. For kinetic measurements, temperature and pressure were varied. As reaction intermediates, adsorbed sulfite and sulfate were identified. An increase of the temperature from 27°C to 77°C led to a more pronounced oxidation of sulfide (Fig. 19.15). 

The removal of inorganic salts from reaction mixtures afforded by polymeric materials may be simply and effectively accomplished by dialysis,166 178 after decomposition of remaining periodate with ethylene glycol130 131 or butylene glycol. 161 170 Alternatively, the iodate and periodate ions may be removed as such, or after reduction to free iodine. The iodate and periodate ions have been effectively precipitated by means of sodium carbonate plus manganous sulfate,6 or by lead dithionate,191 barium chloride,24 192 193 strontium hydroxide194 202 or barium hydroxide,203 204 lead... 

Conversely, exposure to hydrogen fluoride at 0 °C over short periods of time leads to almost quantitative hydrolysis.[37-39] In aprotic organic solvents, decomposition takes place unless the sulfate hemi-ester is neutralized with strong counterions.[37,381 The results of a detailed study are summarized in Figures 1 and 2t4°l which show the effect of various acids used in peptide chemistry in deprotection and in cleavage from the resin as well as the effect of temperature on the hydrolysis of tyrosine 0-sulfate as a sodium salt. 

The decomposition of the diazonium sulfate in the presence of alcohol may take place with considerable violence, and it is necessary to watch the reaction carefully so as to be able to check it, if necessary, by the external application of cold water. Acetaldehyde is rapidly evolved, and some will generally escape from the condenser. It is therefore advisable to lead the escaping gases through water, not only in order to avoid possibility of fire, but to retain any nitrotoluene which may be entrained. 

Ti02 addition to the NSR catalysts leads to an improvement of SOx resistance of the catalyst. Ti02 is an acidic material, and sulfates on Ti02 are less stable than that on alumina. Fience, Ti02 promotes the decomposition and removal of sulfates in reducing conditions. Also, Zr02 2 mixed oxide as a support for -compounds improves the NOx removal activity. 

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