Carbon flame, determination

The Action of Heat.—We will assume in the first 1 ic,. S7. plate that the substance is homogeneous and consists of a single individual. Heat a portion on platinum foil and notice if it volatilises, chars, or burns with a clear, luminous, non-Iuminous (aliphatic), or smoky (aromatic) flame. Determine the nature of the residue, if any, when the carbon has burnt away. 

In order to maintain high energy efficiency and ensure a long service life of the materials of construction in the combustion chamber, turbine and jet nozzle, a clean burning flame must be obtained that minimizes the heat exchange by radiation and limits the formation of carbon deposits. These qualities are determined by two procedures that determine respectively the smoke point and the luminometer index. 

At still higher temperatures, when sufficient oxygen is present, combustion and "hot" flames are observed the principal products are carbon oxides and water. Key variables that determine the reaction characteristics are fuel-to-oxidant ratio, pressure, reactor configuration and residence time, and the nature of the surface exposed to the reaction 2one. The chemistry of hot flames, which occur in the high temperature region, has been extensively discussed (60-62) (see Col ustion science and technology). 

A flame-ionization, total hydrocarbon analyzer determines the THC, and the total carbon content is calculated as methane. Other methods include catalytic combustion to carbon dioxide, which may be deterrnined by a sensitive infrared detector of the nondispersive type. Hydrocarbons other than methane and acetylene are present only in minute quantities and generally are inert in most appHcations. 

Various types of detector tubes have been devised. The NIOSH standard number S-311 employs a tube filled with 420—840 p.m (20/40 mesh) activated charcoal. A known volume of air is passed through the tube by either a handheld or vacuum pump. Carbon disulfide is used as the desorbing solvent and the solution is then analyzed by gc using a flame-ionization detector (88). Other adsorbents such as siUca gel and desorbents such as acetone have been employed. Passive (diffuse samplers) have also been developed. Passive samplers are useful for determining the time-weighted average (TWA) concentration of benzene vapor (89). Passive dosimeters allow permeation or diffusion-controlled mass transport across a membrane or adsorbent bed, ie, activated charcoal. The activated charcoal is removed, extracted with solvent, and analyzed by gc. Passive dosimeters with instant readout capabiUty have also been devised (85). 

For selective estimation of phenols pollution of environment such chromatographic methods as gas chromatography with flame-ionization detector (ISO method 8165) and high performance liquid chromatography with UV-detector (EPA method 625) is recommended. For determination of phenol, cresols, chlorophenols in environmental samples application of HPLC with amperometric detector is perspective. Phenols and chlorophenols can be easy oxidized and determined with high sensitivity on carbon-glass electrode. 

Part 28 Determination of 1,1,1-trimethylolpropane (TMP) in food simulants Aqueous food simulants are saturated with potassium carbonate and extracted with ethanol/ethyl acetate. After evaporation of solvent the extracted TMP is silyated with trimethylsilylimidazole in pyridine and determined by GC with flame ionisation detection... 

Leek and Bagander [221] determined reduced sulfide compounds (hydrogen sulfide, methyl mercaptan, carbon disulfide, dimethyl sulfide, and dimeth-yldisulfide) in water by gas chromatography using flame detection. Detection limits ranged from 0.2 ng/1 for carbon disulfide to 0.6 ng/1 for methyl mercaptan. Hydrogen sulfide was determined at the 1 ng/1 level. 

Leek and Baagander [311] determined reduced sulfide compounds in seawater by gas chromatography using a flame ionisation detector. Substances determined include methyl mercaptan, dimethyl sulfide, hydrogen sulfide and carbon disulfide. Detection limits range from 0.2ng/l (carbon disulfide) to 0.6 ng/1 (methyl mercapton). 

Amino acids can be determined in a two-step process (reaction 26). The SO2 produced can be determined by measuring the S2 emission of an N2-H2 flame in a molecular emission cavity. Carbon was found to be better than iron for building the cavity376. 

Cavendish s papers next described experiments with carbon dioxide, which he called fixed air. He studied its solubility in water and its efficacy in extinguishing flames. He concluded that when one part carbon dioxide was mixed with eight parts of ordinary air, candles would not burn. He also determined the density of carbon dioxide, finding that it was about 50 percent heavier than air. This result is astonishingly close to the modern value of 52 percent. 

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