Flame volatile sodium

On cooling some devitrification occurs and the rate of sintering depends largely on the ratio of glassy phase to crystalline species in the ash. The flame volatile sodium captured by the vitrified silicate particles can initiate the coalescence of deposited ash by viscous flow and the rate of sintering is markedly increased by the alkali-metal dissolved in the glassy phase. 

The distribution of the flame volatile sodium between the ash silicate and sulphate phases is markedly influenced by the temperature and residence time of the ash particles in the flame. 

Some of the flame volatile sodium is dissolved in the vitrified silicate ash particles before deposition and an additional amount of sodium is transferred from the sulphate to silicate phases during sintering. The reaction between sodium sulphate and silicates at ash sintering temperatures has been monitored by thermo-gravimetric measurements. Some of the results are given in Table IV. 

The fused silicate particles will absorb the flame volatilized sodium to the depth of about 0.05 pm (10), and the remainder is converted to sulphate partly in the flue gas and partly at the surface of ash particles. The distribution of sodium in the silicate and sulphate phases can be expressed in a form ... 

All coals contain some sodium combined in the alumino-silicate species which will remain largely involatile in the flame. The ratio of the silicate sodium to non-silicate sodium varies over a wide range. The alkali-metal is present chiefly in the silicates in low chlorine bituminous coals. In the high chlorine bituminous coals and in many lignites and sub-bituminous coals it is present mainly in a flame volatile form. 

The high temperature of large boiler flame reduces the viscosity of vitrified silicate particles and as a result a large fraction of the volatile sodium is dissolved in the silicate phase. On average 60 per cent of the sodium is dissolved in the silicate ash particles the remainder being present as sulphate fume particles in the flue gas (8). 

Flame Volatile and Silicate Sodium in Coal. Sodium is rapidly volatilized in the flame when it occurs in a non-silicate compound form, chiefly associated with chlorine in bituminous coals and combined with organic compounds in the lignite and sub-bituminous fuels. The fraction of sodium combined with coal silicates remains largely involatile in the pulverized fuel flame. 

The staff, employees of the inner part of flue walls withstands thermal shock, abrasion of the coke, and the influence of the reduction atmosphere. A CO and CO2 atmosphere is combined with action of volatile sodium and fluorine compounds from the carbon anode butts. The material inside the flue walls interacts only with flame gases from the burning of natural gas and heavy oil. The usual requirements to the refractories for the flue walls are thermal shock resistance, minimal shrinkage, and high temperature of the deformation under the load [3-7]. 

The residue (5) in the distilhng flask may stUl contain a water-soluble, non-volatile acid. Cool the acid solution, neutralise it with dilute sodium hydroxide solution to Congo red, and evaporate to dryness on a water bath under reduced pressure (water pump). Heat a httle of the residual salt (G) upon the tip of a nickel spatula in a Bunsen flame and observe whether any charring takes place. If charring occurs, thus... 

A number of elements form volatile hydrides, as shown in the table. Some elements form very unstable hydrides, and these have too transient an existence to exist long enough for analysis. Many elements do not form stable hydrides or do not form them at all. Some elements, such as sodium or calcium, form stable but very nonvolatile solid hydrides. The volatile hydrides listed in the table are gaseous and sufficiently stable to allow analysis, particularly as the hydrides are swept into the plasma flame within a few seconds of being produced. In the flame, the hydrides are decomposed into ions of their constituent elements. 

Although electrothermal atomisation methods can be applied to the determination of arsenic, antimony, and selenium, the alternative approach of hydride generation is often preferred. Compounds of the above three elements may be converted to their volatile hydrides by the use of sodium borohydride as reducing agent. The hydride can then be dissociated into an atomic vapour by the relatively moderate temperatures of an argon-hydrogen flame. 

Tin compounds are converted to the corresponding volatile hydride (SnH4, CH3 SnH3, (CH3 )2 SnH2, and (CH3 >3 SnH) by reaction with sodium borohydride at pH 6.5 followed by separation of the hydrides and then atomic absorption spectroscopy using a hydrogen-rich hydrogen-air flame emission type detector (Sn-H band). 

To a flame-dried, three-neck, 1-1 flask were added, in order, p-xylene (107 g, 1.0 mol), phosphorus trichloride (412 g, 3.0 mol), and anhydrous aluminum chloride (160 g, 1.2 mol). The reaction mixture was slowly heated to reflux with stirring. After 2.5 h at reflux, the reaction was allowed to cool to room temperature and the volatile components distilled at reduced pressure. The residual oil was slowly added to cold water (1 1) with stirring, and a white solid formed. The solid was removed by filtration, washed with water, and air dried. The solid was suspended in water (1 1) to which was added 50% sodium hydroxide solution (90 ml) to cause dissolution. The solution was saturated with carbon dioxide and filtered through Celite . The basic solution was washed with methylene chloride (200 ml) and acidified with concentrated hydrochloric acid (200 ml). The white solid that separated was isolated by extraction with methylene chloride (3 x 250 ml). The extracts were dried over magnesium sulfate, filtered, and evaporated under reduced pressure to give the pure 2,5-dimethylbenzenephosphinic acid (99 g, 60%) as an oil, which slowly crystallized to a solid of mp 77-79°C. 

Liquid sodium is a volatile substance that can burst into flames if it comes into contact with either air or water. An early liquid sodium-cooled breeder reactor, the Fermi I, had a melting accident when 2% of the core melted after a few days of operation. Four years later when the reactor was about to be put into operation again a small liquid sodium explosion occurred in the piping. 

Fuel, oxygen, and high temperature are essential for the combustion process. Thus, polyfluorocarbons, phosphazenes, and some composites are flame-resistant because they are not good fuels. Fillers such as alumina trihydrate (ATH) release water when heated and hence reduce the temperature of the combustion process. Compounds such as sodium carbonate, which releases carbon dioxide when heated, shield the reactants from oxygen. Char, formed in some combustion processes, also shields the reactants from a ready source of oxygen and retards the outward diffusion of volatile combustible products. Aromatic polymers, such as PS, tend to char and some phosphorus and boron compounds catalyze char formation aiding in controlling the combustion process. 

Selenium is converted to its volatile hydride by reaction with sodium boro-hydride, and the cold hydride vapor is introduced to flame AA for analysis. Alternatively, selenium is digested with nitric acid and 30% H2O2, diluted and analyzed by furnace-AA spectrophotometer. The metal also may be analyzed by ICP-AES or ICP/MS. The wavelengths most suitable for its measurements are 196.0 nm for flame- or furnace-AA and 196.03 nm for ICP-AES. Selenium also may be measured by neutron activation analysis and x-ray fluorescence. 

According to B. Schindler,16 potassium iodide volatilizes in free air when heated to the softening temp, of hard glass, and, according to B. Bunsen, and T. H. Norton and D. M. Both, it volatilizes from 0-352 to 0-423 times as fast as the same quantity of sodium chloride when heated in the hottest part of a Bunsen s flame. According to J. Dewar and A. Scott,17 the vapour density of potassium iodide is 169 8. A. von Weinberg obtained 43"3 Cals, for the heat of sublimation of sodium iodide, and 44 9 Cals, for that of potassium iodide and A. Beis obtained for sodium and potassium iodides respectively 51 and 46 Cals., and between 15 and 35 Cals, for lithium iodide. 

The volatility of lithium carbonate was studied by R. Bunsen he found that this compound volatilizes in the hottest part, of a Bunsen flame 8 74 (and by T. H. Norton and D. M. Roth 10) times as rapidly when melted as the same quantity of sodium chloride. According to L. Troost, lithium carbonate begins to decompose before it melts, and when melted it loses carbon dioxide, rapidly at first, but more slowly later on, until but 17 per cent, of the total remains, and P. Lebeau found that when heated in vacuo, all the carbon dioxide can be driven off, and a part of the resulting oxide is volatilized. P. Lebeau found the dissociation pressure of lithium carbonate to be at ... 

Chemical vaporisation. Some elements (such as arsenic, bismuth, tin and selenium) are difficult to reduce in a flame when they are in higher oxidation states. For these atoms, the sample is reacted with a reducing agent prior to analysis (sodium borohydride or tin chloride in acidic media) in a separate vessel. The volatile hydride formed is carried by a make-up gas into a quartz cell placed in the flame (Fig. 14.10). 

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