Moist air

Silicon tetrachloride. S1CI4 m.p. — TO C, b.p. 57°C. Colourless liquid (Si plus CI2 followed by distillation). Hydrolyses in moist air or in water. 

The trichloride is obtained as a liquid, boiling point 349 K, when a jet of chlorine burns in phosphorus vapour. Care must be taken to exclude both air and moisture from the apparatus since phosphorus trichloride reacts with oxygen and is vigorously hydrolysed by water, fuming strongly in moist air. The hydrolysis reaction is ... 

Sulphur oxide dichloride is a colourless liquid which fumes in moist air. It is hydrolysed by water to give a mixture of sulphurous and hydrochloric acids ... 

Properties—Hydrogen iodide is a colourless gas. It is very soluble in water and fumes in moist air (cf. hydrogen chloride), to give hydriodic acid. Its solution forms a constant boiling mixture (cf. hydrochloric and hydrobromic acids). Because it attacks mercury so readily, hydrogen iodide is difficult to study as a gas, but the dissociation equilibrium has been investigated. 

ChloricfVII) acid fumes in moist air and is very soluble in water, dissolving with the evolution of much heat. Several hydrates are known the hydrate HCIO4. H2O is a solid at room temperature and has an ionic lattice [HjO ] [CIO4]. 

Physical properties. Colourless liquids when pure, benzoyl chloride, CjHjCOCl, is frequently pale yellow. Acetyl chloride, CH3COCI, has a pungent odour, fumes in moist air and is immediately hydrolysed by cold water. Benzoyl chloride also has a pungent odour, is lachry matory, and is hydrolysed only slowly by cold water, in which it is insoluble. 

Technetium is a silvery-gray metal that tarnishes slowly in moist air. The common oxidation states of technetium are +7, +5, and +4. Under oxidizing conditions technetium (Vll) will exist as the pertechnetate ion, TcOr-. The chemistry of technetium is said to be similar to that of rhenium. Technetium dissolves in nitric acid, aqua regia, and cone, sulfuric acid, but is not soluble in hydrochloric acid of any strength. The element is a remarkable corrosion inhibitor for steel. The metal is an excellent superconductor at IIK and below. 

Cerium is an iron-gray lustrous metal. It is malleable, and oxidizes very readily at room temperature, especially in moist air. Except for europium, cerium is the most reactive of the rare-earth metals. It decomposes slowly in cold water and rapidly in hot water. 

The metal is relatively stable in dry air, but tarnishes in moist air and forms a losely adhering... 

Pure holmium has a metallic to bright silver luster. It is relatively soft and malleable, and is stable in dry air at room temperature, but rapidly oxidizes in moist air and at elevated temperatures. The metal has unusual magnetic properties. Few uses have yet been found for the element. The element, as with other rare earths, seems to have a low acute toxic rating. 

The density of moist air depends upon the temperature, the humidity, and the barometric pressure. It is expressed by the equation... 

The refractive index of moist air can be calculated from the expression... 

Thermodynamic principles govern all air conditioning processes (see Heat exchange technology, heat transfer). Of particular importance are specific thermodynamic appHcations both to equipment performance which influences the energy consumption of a system and to the properties of moist air which determine air conditioning capacity. The concentration of moist air defines a system s load. 

Psychrometrics. Psychrometrics is the branch of thermodynamics that deals specifically with moist air, a biaary mixture of dry air and water vapor. The properties of moist air are frequentiy presented on psychrometric charts such as that shown ia Figure 2 for the normal air conditioning range at atmospheric pressure. Similar charts exist for temperatures below 0°C and above 50°C as well as for other barometric pressures. AH mass properties ate related to the mass of the dry air. 

Saturation Temperature. The temperature at which the water vapor in moist air is in equiUbrium with Hquid water. 

In contact with moist air, molten cryohte loses HF and is depleted in A1F.. 

Although stable at ambieat temperature, calcium fluoride is slowly hydrolyzed by moist air at about 1200°C, presumably to CaO and HF. Calcium fluoride is not attacked by alkahes or by reactive fluorine compounds, but is decomposed by hot, high boiling acids, as ia the reactioa with coaceatrated sulfuric acid which is the process used to produce hydrogea fluoride. Calcium fluoride is slightly soluble ia cold dilute acids, and somewhat more soluble ia solutioas of alumiaum hahdes. 

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