Barium carbonate, decomposition

Barium nitrite [13465-94-6] Ba(N02)2, crystallines from aqueous solution as barium nitrite monohydrate [7787-38-4], Ba(N02)2 H2O, which has yellowish hexagonal crystals, sp gr 3.173, solubihty 54.8 g Ba(NO2)2/100 g H2O at 0°C, 319 g at 100°C. The monohydrate loses its water of crystallization at 116°C. Anhydrous barium nitrite, sp gr 3.234, melts at 267°C and decomposes at 270 °C into BaO, NO, and N2. Barium nitrite may be prepared by crystallization from a solution of equivalent quantities of barium chloride and sodium nitrite, by thermal decomposition of barium nitrate in an atmosphere of NO, or by treating barium hydroxide or barium carbonate with the gaseous oxidiation products of ammonia. It has been used in diazotization reactions. 

Both carbonates decompose to their oxides with the evolution of carbon dioxide. The decomposition temperature for calcium carbonate is in the temperature range 650-850 °C, whilst strontium carbonate decomposes between 950 and 1150°C. Hence the amount of calcium and strontium present in a mixture may be calculated from the weight losses due to the evolution of carbon dioxide at the lower and higher temperature ranges respectively. This method could be extended to the analysis of a three-component mixture, as barium carbonate is reported to decompose at an even higher temperature ( 1300 °C) than strontium carbonate. 

Barium acetate converts to barium carbonate when heated in air at elevated temperatures. Reaction with sulfuric acid gives harium sulfate with hydrochloric acid and nitric acid, the chloride and nitrate salts are obtained after evaporation of the solutions. It undergoes double decomposition reactions with salts of several metals. For example, it forms ferrous acetate when treated with ferrous sulfate solution and mercurous acetate when mixed with mercurous nitrate solution acidified with nitric acid. It reacts with oxahc acid forming barium oxalate. 

Barium carbonate decomposes to barium oxide and carbon dioxide when heated at 1,300°C. In the presence of carbon, decomposition occurs at lower temperatures. Barium carbonate dissolves in dilute HCl and HNO3 liberating CO2. Similar reaction occurs in acetic acid. The solid salts, chloride, nitrate and acetate that are water soluble may be obtained by evaporation of the solution. Dissolution in HF, followed by evaporation to dryness, and then heating to red heat, yields barium fluoride. 

Barium hydroxide decomposes to barium oxide when heated to 800°C. Reaction with carbon dioxide gives barium carbonate. Its aqueous solution, being highly alkahne, undergoes neutrahzation reactions with acids. Thus, it forms barium sulfate and barium phosphate with sulfuric and phosphoric acids, respectively. Reaction with hydrogen sulfide produces barium sulfide. Precipitation of many insoluble, or less soluble barium salts, may result from double decomposition reaction when Ba(OH)2 aqueous solution is mixed with many solutions of other metal salts. 

Decomposition of the organics leads then to the separation of all elements into Cu and Y oxides and barium carbonate. This brings the synthesis parameters back to the problems encountered in the conventional solid state approach except that the heterogeneity may be over a submicron scale. Thus, reaction temperature may be slightly lowered (850°C instead of 900°C). 

The acid is even less stable than selenotrithionic acid its aqueous solution decomposes in the light or on warming in fact, it cannot even be preserved in the dark. Acids and alkalis also bring about its decomposition. Treatment with barium carbonate, as in the case of the preceding acid, gives a solution of the barium salt which, however, is less stable than barium selenotrithionate, and the solution decomposes slowly in the dark. 

Barium Cobalti-cyanide, Ba3[Co(CN)s]2. Aq., is a convenient starting-point for the preparation of other metallic cobalti-cyanides by double decomposition. It may be prepared by adding barium carbonate to a solution of the free acid but a better method consists in exposing to aerial oxidation a mixture of cobalt sulphate and the cyanides of hydrogen and barium. The salt crystallises out in colourless prisms, winch are readily soluble in water, but not in alcohol. They contain some 20 or 22 molecules of water.4... 

Strontium carbonate is somewhat less soluble than barium carbonate otherwise its characteristics (slight solubility in ammonium salts, decomposition with acids) are similar to those of the latter. 

Barium ferricyanide, Ba3[Fe(CN)6]2.20H2O, is prepared by neutralising ferricyanic acid with barium carbonate and evaporating to crystallisation in vacuo.2. It also results on boiling a solution of barium ferrocyanide with lead dioxide.4 It yields reddish brown crystals. These are soluble in water without decomposition. The salt is decomposed on warming with acids. The compound Ba3[Fe(CN)6]2.2BaBr2. 20H2O, has been obtained.5... 

All of these complexes decompose cleanly at low temperature to produce acetonitrile, carbon dioxide, and initially, the metal hydroxide (equation 45). The decomposition temperatures are 144,176, and 198 °C for Ba, Cu, and Y, respectively. In the case of copper and yttrium, the final product is the metal oxide produced by the dehydration of the hydroxide, while barium hydroxide recombines with carbon dioxide to yield the carbonate. Barium carbonate formation can be avoided, however, by use of a different ligand that avoids carbon dioxide formation. Benzoin a-oxime (Hbo) (13) has been found to be a quite suitable diprotic ligand for this purpose. The barium salt is easily prepared by reaction of the oxime with the metal dihydride (equation 46), and it decomposes cleanly to barium oxide by loss of benzaldehyde and benzonitrile at 250 °C (equation 47). 

Violent reaction with benzoyl chloride combined with KOH, Bt2, barium carbonate, CS2, Cr(OCl)2, Cu, Pb, HNO3, BaCOs, H2SO4, hot water, (CH3)2S04, dibromomalononitrile, sulfuric acid. Incompatible with acids, ammonium chloride + trichloroacetonitrile, phosgene, cyanuric chloride, 2,5-dinitro-3-methylbenzoic acid + oleum, trifiuroroacryloyl chloride. Reacts with heavy metals (e.g., brass, copper, lead) to form dangerously explosive heavy metal azides, a particular problem in laboratory equipment and drain traps. When heated to decomposition it emits very toxic fumes of NOx and Na20. See also AZIDES. 

The anhydrides can be prepared by the action of acetic anhydride on the corresponding malonic acid in the presence of a small amount of sulfuric acid, followed by neutralization of the mineral acid with powdered barium carbonate and evaporation to dryness in a high vacuum. The residual malonic anhydride is then heated to the decomposition point at a low pressure, and the ketene is collected in a cold receiver. This procedure has been applied to the synthesis of low-molecular-weight dialkylketenes (R is methyl, ethyl, f2-propyl, or isopropyl) in 50-80% yields. ... 

The decomposition of barium carbonate requires higher temperatures [38] and the reaction in the solid state below 1300 K is influenced by the prevailing pressure of CO2, while above 1300 K decomposition proceeds in a melt. 

L vov and Novichikhin [39] conclude that the decomposition of barium carbonate at 1200 K can be expressed as ... 

Thermal decompositions of barium and strontium azides, preirradiated with 1 MeV gamma rays, were conducted by Prout and Moore [78,79]. With dehydrated barium azide a total gamma dose of 20 Mrad (2.24 X 10 R) eliminated the induction period and increased the acceleration of the decomposition. A somewhat greater effect was evidenced with strontium azide. Avrami et al. [80] subjected barium azide to Co gamma radiation to exposure levels up to 1 XIO R (Table XIII). Differential thermal analyses (Figure 16) showed a steady decomposition of the sample, and after 1 X 10 R exposure (W hr at room temperature), infrared analysis indicated that the residue was in the form of barium carbonate. 

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