Lead carbonates, decompositions

Azocarbonamide (I) Carbonamide N2, CO, CO2 190-230 220 Most widely used blowing agent in PVC and polyolefins. High decomposition temperature reduced by a variety of metal salts and oxides such as lead carbonate, lead phosphite and zinc oxide. High gas yield. Reaction products show little odour or discoloration. ... 

Sulphur dioxide Sulphur hexafluoride C T O Most common metals for dry gas. Lead, carbon, aluminium and stainless steel for moist gas Most common metals. Copper, stainless steel and aluminium are resistant to the decomposition products at 150°C Zinc... 

Heating many solid carbonates leads to decomposition. What products are obtained Suppose CaCS3 were heated strongly. What would happen ... 

Roast 2-3 g of lead carbonate at 450-500 °C in a porcelain bowl. When decomposition of the salt terminates, roast the substance at the same temperature for another two or three hours. Next transfer the product into a beaker and boil it several times with a lead acetate solution. Pour off the solution from the precipitate, filter off the latter, wash it with hot water, and dry it in a drying cabinet at... 

Cross-linked polystyrene can be directly brominated in carbon tetrachloride using bromine in the presence of Lewis acids (Experimental Procedure 6.2 [55-58]). Thal-lium(III) acetate is a particularly suitable catalyst for this reaction [59]. Harsher bro-mination conditions should be avoided, because these can lead to decomposition of the polymer. Considering that isopropylbenzene is dealkylated when treated with bromine to yield hexabromobenzene [60], the expected products of the extensive bromi-nation of cross-linked polystyrene would be soluble poly(vinyl bromide) and hexabromobenzene. In fact, if the bromination of cross-linked polystyrene is attempted using bromine in acetic acid, the polymer dissolves and apparently depolymerizes [61]. 

Lewis bases often leads to decomposition, and thus rapid hydrolysis in water, unlike carbon halides, which are kinetically more inert. 

The establishment of the stoichiometries for the dissociations of carbonates other than those of Group IIA cations is less straightforward. Some of the intermediate phases recognized in the decomposition of lead carbonate may result from the... 

The reaction of silylated fluoromethylphosphonate carbanions with a large variety of alkyl, vinyl, or aryl chloroformates or with carbon dioxide proceeds smoothly at low temperature to give silylated l-(alkoxycarbonyl)-l-fluoromethylphosphonates and 1-(hydroxycarbonyl)-1-fluoromethylphosphonate, respectively (Scheme 3.58). For the electron-withdrawing carboxyl group, the traces of base already present in the reaction medium are sufficient to effect a desilylation if EtOH is added to the mixture. The desilylated products are isolated in 80-91% yields." - " The addition of EtOLi leads to decomposition with loss of phosphate. 

Alpha-lead azide crystals, wrapped in a thin aluminum foil, were subjected to fast and thermal neutrons in a heavy-water reactor [53]. With a thermal flux rate of about 10 n/cm /sec, the crystals were irradiated for 8, 17, and 170 hr. The crystals decomposed to a brown powder, which was identified as lead carbonate by X-ray diffraction and infrared absorption. From a mass spectrographic analysis of the isotopes of carbon and oxygen in the decomposition products, it was determined that the carbonate was formed fiom the atmosphere by the breaking of surface bonds by the neutrons. It was subsequently reported [54] that the total dose required for conversion to lead carbonate is approximately 7.5 X 10 n/cm ... 

Radiation-induced changes in a-lead azide caused by X-rays were noted by Todd and Party [88, 89]. The hardness was changed by exposure to soft X-rays. With an X-ray dose rate of 1.4 X 10 R/min in air, the decomposing crystal expanded prefentially along the b axis of its crystal structure. More than 97% de-stmction of the azide was achieved with a total dose of 3.4 X 10 R. It was also shown that the stable endproduct of X-ray decomposition in air was basic lead carbonate of the formula 2PbCO3 Pb(OH)3. After a dose of 6.7 X lO R, there was evidence of residual lead azide together with an unidentified phase. Higher doses produced a further unidentified phase before stable basic lead carbonate was finally formed. 

All halides EX4 form tetrahedral molecules (point group Td). Mixed halides are known, as well as fully or partially halogen-substituted catenated alkanes, silanes and germanes (e.g. Ge2Cl6). Unlike the carbon compounds, halides of Si and Ge are Lewis acids and readily form complexes such as [SiF6]. Attack by Lewis bases often leads to decomposition, and thus rapid hydrolysis in water,... 

LEAD CARBONATE (598-63-0) Contact with hot water, acids, acid fumes, or lead oxide causes decomposition with formation of carbon dioxide. Incompatible with acids, ammonia, fluorine, germanium, hydrozoic acid, lead diacetate, magnesium, mercurous chloride, methyl isocyanoacetate, silver nitrate, sodium peroxyborate, titanium, trinitrobenzoic acid, urea nitrate. 

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