Potassium bicarbonate, decomposition

Potassium Bicarbonate. Potassium bicarbonate has become available in commercial quantities for food use. The only reason for using it is that the sodium content of the resulting product is reduced. As the molecular weight of potassium bicarbonate is greater (100.11 for KHC03 compared with 84.01 for NaHC03) some 19% more is required to produce the same volume of carbon dioxide. Potassium bicarbonate is also more expensive. The reaction for its thermal decomposition is ... 

The generally accepted mechanisms for the suppression of fires and explosions by alkali metal salts such as potassium chloride, KCl potassium bicarbonate, KHCO3 and potassium carbonate,K2C03 in the form of dry powders or aerosols (smokes) involve heat absorption, endothermic decomposition and radical recombination. 

To a solution of 2.00 grams (0.00454 mole) of K[Cr(HO-A)2] in 200 ml. of water, cooled to 6° C., were added 12.8 grams of benzoyl chloride and a solution of 2.00 grams of potassium bicarbonate in 20 ml. of water. This mixture was stirred in an ice bath for 30 minutes and then for an additional hour out of the bath. The solution was acidified with concentrated nitric acid, and then filtered to remove benzoic acid. From the filtrate only starting material (infrared spectrum ) and its decomposition products could be isolated. 

Potassium Uranyl Carbonate, K4U02(C03)a, may be prepared by the action of carbon dioxide on potassium uranyl cyanide, or by evaporating at moderate temperature a solution containing potassium bicarbonate and potassium uranate. It crystallises in small hexagonal prisms, which are stable in dry air and dissolve in cold water without decomposition. The solution is hydrolysed on warming, and the addition of alkali causes j recipitation of uranyl hydroxide. 

Put in the presence of water this salt decomposes the carbonate of magnesium, almost insoluble, is deposited while the potassium bicarbonate is dissolved when the solution of potassium bicarbonate is sufficiently concentrated, the decomposition stops and equilibrium is established. 

Several a-fluorenals 61 have been tested the use of TBAI led to enal decomposition, and higher yields were noted with potassium bicarbonate than with potassium carbonate. Under these optimized conditions, the a-fluoro acids 62 (R = aryl, heteroaryl, cyclohexane) were obtained with correct yields and good enantioselectivities. 

Aliphatic and aromatic imino ester hydrochlorides are most easily obtained by passing dry hydrogen chloride into an equimolar mixture of a nitrile and an alcohol in ether solution. Strictly anhydrous conditions ate essential for successful conversions. The time of reaction is greatly reduced by refluxing the ether solution. Dioxane is superior as a solvent in certain cases. At temperatures above 60-80°, decomposition of the imino ester hydrochloride to an alkyl chloride and an amide occurs. The free imino esters are obtained by neutralization of the hydrochlorides with sodium bicarbonate or potassium carbonate under ether. 

MgC03+K2C03-f CO2+5H2O, or treated with magnesium hydroxide below 20 . The soln. of potassium carbonate is filtered ofi the magnesium carbonate and carbon dioxide are used for the treatment of more potassium chloride. The decomposition proceeds better under half an atm. press., and at a temp, over 115 , since the magnesium carbonate is then in a form which filters easily, and the formation of bicarbonates is avoided. 

Ewins s Method o-i-o-2 gm. of the substance is mixed in a 300 ml. Kjeldahl flask with 10 gm. potassium sulphate, o>2-o-3 gm. starch and 20 ml. concentrated sulphuric acid. This mixture is then heated by means of a Bunsen burner, first moderately for 10-15 minutes, then more vigorously for about 4 hours, until decomposition is complete. The liquid is cooled, transferred to a 350 ml. flask and made alkaline to litmus paper with sodium hydroxide. It is then cooled to 30° to 40° and sulphuric acid added drop by drop until the solution is faintly acid. A saturated solution of sodium bicarbonate is then added until the solution is again alkaline, 5-10 ml. being added in excess. The arsenious acid formed is then titrated with iodine solution using starch as indicator. 

Use is made of this double decomposition in the technical preparation of potassium nitrate from Chih saltpetre. Four salts connected by an equation of the above kind are caUed reciprocal pairs of salts. A further example of this kind is the manufacture of sodium bicarbonate by the Solvay process, viz. 

Tropinone is a low melting tertiary base which readily forms a methio-dide. The decomposition of this methiodide in alkali, in contrast to that of tropine and tropidine, does not give the expected des-base. With potassium hydroxide resinification of the primary product occurs (129) however, with silver oxide (128) or sodium bicarbonate (129) a product thought to be A -dihydrobenzaldehyde (oxime and phenylhydrazone (117)) was isolated in good yield. (This sensitivity towards alkali is a general characteristic of -aminocarbonyl compounds.) Silver oxide oxidizes this aldehyde to a dihydrobenzoic acid, while at elevated temperatures benzoic acid is formed. 

There is a striking solubility difference between the potassium and sodium salts of tricarbonatocobaltate(III). The concentration of the solution prepared according to Procedure 1 can be made as high as 1 mol/dm with respect to Co(III) however the potassium salt can be isolated only with simultaneous decomposition to hydrous-oxidc-like substances. In contrast, the sodium salt obtained by Procedure 2 is very stable when it is completely dried. The salt is insoluble in water but soluble in water containing sodium bicarbonate. 

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