Iodine standard pressure

Standard pressure, 54 Standard state, 210 Standard temperature, 54 Starch, 425 iodine test, 358 structure, 431 Stars, 447... 

A FIGURE 11.2 Oases, liquids, and solids. Chlorine, bromine, and iodine are all made up of diatomic moiecuies as a resuit of covaient bonding. However, due to differences in the strength of the intermoiecuiar forces, they exist in three different states at room temperature and standard pressure Ci2 gaseous, Br2 iiquid, i2 soiid. 

The Model 835 multiwavelength filter photometer (Fig.3.44) provides energy at 254 nm with a low-pressure mercury lamp and at 280,313,334 and 365 nm with a medium-pressure mercury source. Selected wavelengths between 380 and 650 nm are also available with a quartz-iodine light source. Absorbance ranges of 0.01-2.56 AUFS are provided. Short-term noise levels are 5 X 10-s AU with the low-pressure mercury source and 1 X 10 4 AU with the other lamps. The design and dimensions of the cell are the same as for Model 840. A 24-jtzl cell is standard with the medium-pressure mercury lamp and the quartz—iodine lamp. 

Air and gaseous S02 in the required ratio enter Mixer 6 to mix fully with each other, and the resulting pseudo flue gas is divided into two equal streams to enter Absorber 7. The air flow rate is adjusted by a butterfly valve in the pipeline and measured with a Pitot tube-pressure difference meter and that of S02 by the rotameter 5. The total gas flow rate is also monitored by a wind velocity meter of DF-3 type at the gas outlet of the reactor. For each run, gas-samplings are made at both inlet and outlet of the reactor, and the S02 concentrations in the samples are measured with the Iodine-quantitative method, a standard and authentic method of determining the integral amount of S02 absorbed in the reactor. 

In the first reaction, 393.51 kJ are liberated (exothermic reaction) when 1 mol of gaseous C02 is formed from graphite and oxygen. When 2 mol HI are formed from gaseous hydrogen and solid iodine, there are 52.72 kJ absorbed (endothermic reaction). In the case of the second reaction, the standard heat of formation is +26.36 kJ/mol HI formed the total amount of energy involved in the reaction as written is twice the standard heat of formation because there were two moles of product formed. The reason why AH is the symbol instead of AHf is that the reaction does not address the formation of one mole of product therefore, AHf, which is calculated on a per-mole basis, is not an appropriate symbol for the reaction. Further, notice that the 0 is used in AHj and with other factors (S°, AGp or AE°) to indicate the standard condition of pressure, 1 atm (1 bar), usually 25°C and, for dissolved substances, of concentration 1 molal (refer to Chapter 12). For easy reference, selected standard heats of formation for selected substances are located in Table 7-1 however, notice that there are no elements listed in the table. 

To a solution of 280 mg of 3a,lip,17,17a-tetrahydroxy-13a-(2-cyanoethyl)-D-homo-18-noretiocholan in 17 ml of methanol at room temperature contained in a 25 ml volumetric flask there was added 162 mg of sodium metaperiodate in 8 ml of water. A small amount of water was added to bring the volume to 25 ml. After 15 min an aliquot was withdrawn and added to a measured amount of sodium arsenite solution containing sodium bicarbonate and potassium iodide. After 10 min, the solution was titrated with standard iodine solution. The solution was diluted with water and extracted twice with ethyl acetate, each extract being washed in turn with sodium combined, dried over magnesium sulfate and concentrated to dryness under reduced pressure, yielding 265 mg of a colorless, amorphous product of 4b-methyl-ip-(2-formylethyl)-2p-formyl-2-(2-cyanoethyl)-4p,7a-dihydroxyperhydrophenanthrene. 

The standard reaction mixture was composed of 5 /aL of Tris-HCl (pH 7.4), 5 /aL of 40 mM NADPH, 5 /aL of sepiapterin reductase (activity of 400 nmol/min/mL), and 65 /aL of cell extract (10-200 /Ag of protein). The reaction was started by the addition of 20 /aL of 0.4 mM 7,8-dihydroneopterin triphosphate. After 30 to 90 minutes of incubation in the dark at 37°C, the reaction was terminated by the addition of 50 /aL of a mixture of 0.2 M HC1 and 0.02 M KI-I2 (11, v/v). The resulting mixture was incubated for 1 hour in the dark to allow oxidation of tetrahydrobiopterin to biopterin. Excess iodine was destroyed by the addition of 50 /aL of 0.02 M ascorbic add. An aliquot of the mixture was applied to a solid phase cartridge (SCX from Analytichem) that had been preequilibrated with 0.1 M H3PO4. The sample was forced through the cartridge with air pressure. The cartridge was then washed with 0.5 mL of 0.1 M H3PO4. The eluates were used for HPLC analysis. Assays were linear with up to 150 fig of cellular protein and 90 minutes of incubation. 

The standard potentials of bromine and iodine have been determined by somewhat similar methods with bromine the results are expressed in terms of two alternative standard states, viz., the gas at 1 atm. pressure or the pure liquid. The standard state adopted for iodine is the solid state, so that the solution is saturated with respect to the solid phase. The acandard potential of fluorine has not been determined by direct experiment, but its value has been calculated from free energies derived from thermal and entropy data. ... 

One atmosphere equals the pressure at the surface of the earth that is due to the weight of the air. Pressure is often reported in units equal to the standard atmosphere. The value of this unit is 14.7 pounds per square inch. This is equal to the pressure produced by the weight of a column of mercury 760 mm high. Pressure is also reported in units equal to the weight of the corresponding column of mercury. The abbreviation mm Hg is used for mm of mercury. The vapor pressure of iodine at its melting point is 90 mm Hg, which is 90/760 atm or 0.118 atm. 

The USDA published what may have been the first practical procedure for quickly determining if a truckload of seed is a linoleic or oleic variety (138). It involves squeezing a few seeds in a small hand-powered press to obtain a few drops of oil. A drop of oil is placed on the glass prism cell of a hand-held refractometer. The refractive index has a straight-line relationship with the iodine value or fatty acid distribution of the oil, hence it is easy to determine if the seed in question meets an oleic standard or not, so long as a temperature correction is applied. Recently, it has become simpler to compare the unknown sample to a known oil standard, eliminating the need to apply a temperature correction. Temperature corrections are difficult to measure accurately in the field under the time pressure of harvest. 

At the given temperature, and for a standard state of 1 mol/L, /( = 50 for the reaction, (a) What is the total pressure in the chamber b) How many moles of the iodine remain unreacted at equilibrium (c) What is the partial pressure of each component in the equilibrium mixture ... 

The Standard Potentials of the Halogens. The standard potential of chlorine, obtained from cells without liquid junctions, has been considered on page 198. The standard potential of iodine has been determined by Maitland and more recently by Jones and Schumb6 and Jones and Kaplan.7 It is most convenient to take the solid as the standard state of iodine, instead of the gas at one atmosphere pressure as was done with chlorine, Jones and Schumb used cells of the type... 

Homologation experiments were conducted in a 300 ml pressure reactor ( M/s Parr Inst., Co. U.S.A ). In a typical run, known amount of catalyst is mixed with known volumes of aqueous HI and methanol (total volume 50 ml) and placed in the reaction vessel. The reactor was pressurized to 30 atm CO and was maintained at 150 C. After 11 h contact time, the reactor was cooled to room temperature and analyzed for the products. Dimethyl ether formation was confirmed by passing the gaseous product through iodine in CS2 solution which gave tany colour. It was quantitatively analyzed by gas chromatography using molecular sieve 13X packed s.s column and TCD detector. Acetic acid and dimethylacetate were analyzed by GC ( Shimadzu, Japan ) and confirmed by their standards. 

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