Double decomposition precipitation reaction

The preliminary investigation on the synthesis of nano hydroxylapatite by double decomposition-precipitation is made with (NHj HPC and Ca(N03)2 as the reactants and the submerged circulative impinging stream reactor (SCISR) as the reaction-precipitation equipment. The following are preliminarily concluded ... 

Garboxylates. Cerium carboxylates, water-insoluble, can be made (11) by double decomposition and precipitation using water-soluble precursors, or by reaction of an insoluble precursor directly with the organic acid. Cerous oxalate [139-42-4] 2-ethyIhexanoate (octanoate),... 

MetaUic soaps are manufactured by one of three processes a fusion process, a double decomposition or precipitate process, or a direct metal reaction (DMR). The choices of process and solvent depend on the metal, the desired form of the product, the desired purity, raw material avadabihty, and cost. 

Double Decomposition. In the double decomposition reaction, an inorganic metal salt such as a sulfate, chloride, acetate, or nitrate reacts with the sodium salt of the carboxyUc acid ia a hot aqueous solution. The metal soap precipitate is filtered, washed, dried, and milled. 

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. 

In an atmosphere of nitric oxide, thermal decomposition produces barium nitrite, Ba(N02)2. Reactions with soluble metal sulfates or sulfuric acid yield barium sulfate. Many insoluble barium salts, such as the carbonate, oxalate and phosphate of the metal, are precipitated by similar double decomposition reactions. Ba(N03)2 is an oxidizer and reacts vigorously with common reducing agents. The solid powder, when mixed with many other metals such as aluminum or zinc in their finely divided form, or combined with alloys such as... 

It undergoes double decomposition reactions in aqueous solution forming precipitates of insoluble products ... 

In aqueous solutions, calcium chloride undergoes double decomposition reactions with a number of soluble salts of other metals to form precipitates of insoluble calcium salts. For example, mixing solutions of calcium chloride with sodium carbonate, sodium tungstate and sodium molybdate solutions precipitates the carbonates, tungstates, and molybdates of calcium, respectively. Similar precipitation reactions occur with carboxylic acids or their soluble salt solutions. CaCb forms calcium sulfide when H2S is passed through its solution. Reaction with sodium borohydride produces calcium borohydride, Ca(BH4)2. It forms several complexes with ammonia. The products may have compositions CaCl2 2NH3, CaCb dNHs, and CaCb SNHs. 

In aqueous solution, the dihydrate, CaS04 2H2O (soluble in water) undergoes double decomposition reactions with other soluble salts, precipitating out insoluble salts ... 

Cobalt(II) chloride undergoes many double decomposition reactions in aqueous solution to produce precipitates of insoluble cobalt salts. For example, heating its solution with sodium carbonate yields cobalt(lI) carbonate ... 

In aqueous solutions, copper(II) nitrate undergoes many double decomposition reactions with soluble salts of other metals, forming precipitates of insoluble copper salts. 

Aqueous solution of lead dichloride also undergoes double decomposition reactions with several metal salts, precipitating insoluble lead salts. 

Magnesium sulfate undergoes three important types of reactions in aqueous solutions double decomposition, double salt formation, and formation of oxysulfate cements. Many insoluble magnesium salts may be precipitated out by double decomposition reactions ... 

Aqueous solution of manganese(ll) sulfate undergoes double decomposition reactions precipitating insoluble manganese(II) salts for example, adding caustic soda solution precipitates manganese(II) hydroxide. 

Mercury(I) nitrate undergoes double decomposition reactions with anions in aqueous solution, forming corresponding mercury(l) salts. With potassium iodide and sodium bromide, yellow mercury(l) iodide and white mercury(I) bromide precipitate, respectively. Similarly, mercury(l) nitrate in acid medium reacts with dilute sulfuric acid to form mercury(1) sulfate ... 

Another type of reaction is double decomposition producing metal hydroxides. Thus, insoluble heavy metal hydroxides may be precipitated by treating caustic soda with a soluble metal salt ... 

Fluorhydroxyapatite can be synthesised by the traditional double-decomposition method generally used for apatite precipitation. An ammonium phosphate and fluoride solution (solution B) is added, dropwise, into a hot (generally at boiling temperature) calcium solution (solution A) at a basic pH level as previously published [122,123]. Fluorapatites close to stoichiometry are obtained (a = 2, see the following reaction equation) however, a very small residual amount of OH always seems to be present. Filtration and several washing operations are necessary to remove the counter-ions. The reaction is almost total due to the very low solubility of fluorhydroxyapatites. 

A number of precipitation processes have been proposed and used in the past including the double decomposition reaction between calcium chloride and sodium carbonate... 

In the common precipitation process, the double decomposition reaction between an inorganic acid and the sodium silicate is employed to yield hydrated silica ... 

The results given in both Table 16.2 and Fig. 16.2 suggest that a certain back-flow (keeping warm) time after reaction-precipitation inside the SCISR is necessary for full double decomposition and/or, probably, surface deactivation of the newly formed particles, while too long a back-flow time leads to the product becoming worse in both purity and appearance. From the results given in Table 16.2 and Fig, 16.2, three to four hours can be considered to be the optimal condition for the back-flow (ageing) time. 

As it is seen in above formula, the reaction proceeds from the left side to the right. In a dilute solution of materials, it is a very common rule of a double decomposition, i.e., the reaction in a dilute solution proceeds to form a substance which has the minimum solubility of all. The firework mixtures, especially when they are consolidated, are not dilute solution, but a solid. However, as described above, they may be thought to be a highly concentrated solution in water because they absorb more or less a very small amount of moisture. Therefore, even in the consolidated state the reaction may proceed to the direction to produce a substance of minimum solubility as it is with the precipitate formation in the dilute solution. However, it takes a long time, several days, months or years because of few active ions. In this article the author calls this reaction rule as the "minimum solubility law."... 

---