Potassium bromide, properties

There is convincing experimental evidence for the following important statement. To a degree of approximation satisfactory for most analytical work, the mass absorption coefficient of an element is independent of chemical or physical state. This means, for example, that an atom of bromine has the same chance of absorbing an x-ray quantum incident upon it in bromine vapor, completely or partially dissociated in potassium bromide or sodium bromate in liquid or solid bromine. X-ray absorption is predominantly an atomic property. This simplicity is without parallel in absorptiometry. 

The salt effects of potassium bromide and a series office symmetrical tetraalkylammonium bromides on vapor-liquid equilibrium at constant pressure in various ethanol-water mixtures were determined. For these systems, the composition of the binary solvent was held constant while the dependence of the equilibrium vapor composition on salt concentration was investigated these studies were done at various fixed compositions of the mixed solvent. Good agreement with the equation of Furter and Johnson was observed for the salts exhibiting either mainly electrostrictive or mainly hydrophobic behavior however, the correlation was unsatisfactory in the case of the one salt (tetraethylammonium bromide) where these two types of solute-solvent interactions were in close competition. The transition from salting out of the ethanol to salting in, observed as the tetraalkylammonium salt series is ascended, was interpreted in terms of the solute-solvent interactions as related to physical properties of the system components, particularly solubilities and surface tensions. 

Table XVII. Physical Properties of Saturated Solutions of Potassium Bromide and Various Tetraalkylammonium Bromides...

What are the products of the reaction of concentrated sulphuric acid with potassium bromide (See Experiment 13, page 167.) Write the equations. What property possessed by hydrogen bromide, but not by hydrogen chloride, is shown ... 

A first requirement for a substance to produce a taste is that it be water soluble. The relationship between the chemical structure of a compound and its taste is more easily established than that between structure and smell. In general, all acid substances are sour. Sodium chloride and other salts are salty, but as constituent atoms get bigger, a bitter taste develops. Potassium bromide is both salty and bitter, and potassium iodide is predominantly bitter. Sweetness is a property of sugars and related compounds but also of lead acetate, beryllium salts, and many other substances such as the artificial sweeteners saccharin and cyclamate. Bitterness is exhibited by alkaloids such as quinine, picric acid, and heavy metal salts. 

The potassium bromide-pellet method provides the most convenient way to detect a slight polymerizability at room temperature using the following operation a few milligrams of the monomer are embedded in a KBr pellet, and the change upon irradiation is followed by IR spectroscopy. All the polymers thus obtained, their properties and the polymerization conditions are listed in Table 1. 

Experiment 120. — Put three or four crystals of potassium bromide in a test tube, and add a few drops of concentrated sulphuric acid. The white product is hydrobromic acid. Observe its most apparent properties — cautiously. Test the gas with both kinds of litmus paper. Does this product resemble hydrochloric acid Are they similar enough to be closely related Give any evidence of a secondary reaction. 

Add a few drops of silver nitrate solution to potassium bromide solution. Is the solid product soluble in dilute ammonium hydroxide Compare the interaction with the interaction of silver nitrate and chlorides. Do the properties of bromides, typified by potassium bromide, suggest any marked relation to chlorides ... 

The e> planation of the fact that a strong electrolyte such as potassium bromide produces a smaller freezing-point lowering than calculated for complete ionization is that there are strong electrical forces operating between the ions, which decrease their effectiveness, so that the properties of their solutions are different from those of ideal solutions, except at extreme dilution. The interionic attraction reduces the activity of the ions to a value less than their concentration. 

The bromine atom of bromoacetone is easily separated from the molecule and substituted by other atoms or radicles. Thus on treating bromoacetone with alcoholic potash, hydroxyacetone and potassium bromide are obtained with sodium iodide iodoacetone is formed, this being a substance with strongly lachrymatory properties, but of little importance as a war gas because of its high cost. 

The corresponding nitrate crystallises with one molecule of water of crystallisation as a white crystalline compound. The preparation is similar to the sulphate, the sulphuric acid being replaced by 40 per cent, nitric acid. The product is soluble in alkali or ammonium hydroxide, and ammonium sulphide gives a yellow precipitate when added to these solutions. The aqueous solution of the nitrate has an acid reaction, and from it potassium bromide precipitates the bromide quantitatively. When dissolved in 20 per cent, ammonium hydroxide the nitrate gives a white crystalline body containing one molecule of ammonia, which has similar properties to the corresponding sulphate. 

Properties Pale yellow crystals or powder, darkens on exposure to light, finally turning black. D 6.473 (25C), mp 432C, bp decomposes at 700C. Soluble in potassium bromide, potassium cyanide, and sodium thiosulfate solutions very shghtly soluble in ammonia water insoluble in water. 

Potassium bromide, values of properties. See Alkali halides... 

---