Test Isooctane

The motor fuel under test is compared to two pure hydrocarbons chosen as references. The first is 2, 2, 4-trimethylpentane or isooctane which is very resistant to auto-ignition and to which is arbitrarily given the number 100 /... 

Octane number is a measure of a fuel s abiUty to avoid knocking. The octane number of a gasoline is deterrnined in a special single-cylinder engine where various combustion conditions can be controlled. The test engine is adjusted to give trace knock from the fuel to be rated. Various mixtures of isooctane (2,2,4-trimethyl pentane) and normal heptane are then used to find the ratio of the two reference fuels that produce the same intensity of knock as that by the unknown fuel. 

The half-life of the 2,3,7,8-tetrachlorodibenzo-p-dioxin in isooctane was estimated to be 40 min for the 0.5 meter exposure and 3 hours for the one meter exposure. The half-life in 1-octanol was essentially the same. The 24-hour photolysis products of the 2,3,7,8-tetrachlorodibenzo-p-dioxin were examined by gas chromatography. The smallest concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin that could be detected by the instrument was 0.5 ppm. When an injection of the 24-hour photolysis product was made, no tetra was detected. An additional confirmation of the disappearance of the 2,3,7,8-tetrachlorodibenzo-p-dioxin in the 24-hour photolysis products was obtained when thej yiaterial was submitted to the Chemical-Biology Research Laboratory for rabbit testing. No chloracnegenic activity was indicated. ... 

Cleanup of sample extract. Pipet 2.5 mL of the solution derived from Module GPC into a long-necked round-bottom flask or a pear-shaped flask and add 10 mL of isooctane. By rotating the flask slowly, carefully evaporate the solution to ca 1 mL in a rotary evaporator (water-bath temperature set at 30 0 °C). If an odor of ethyl acetate is still present, add isooctane again and repeat the evaporation. Repeat, if necessary, until no odor of ethyl acetate is present the ethyl acetate must be completely removed. Allow the solution to drain to the upper surface of the column packing and then place a graduated test-tube under the column. 

PCBs in biological samples are usually extracted by a Soxhlet column and with a nonpolar solvent such as hexane. The sample is first mixed with sodium sulfate to remove moisture. The extraction of PCBs from sediments was tested with sonication, with two sonications interspersed at a 24-h quiescent interval, with steam distillation, or with Soxhlet extraction (Dunnivant and Elzerman 1988). Comparison of the recoveries of various PCB mixtures from dry and wet sediments by the four techniques and the extraction efficiency of four solvents showed that the best overall recoveries were obtained by Soxhlet extraction and the two sonication procedures. In comparisons of solvent systems of acetone, acetonitrile, acetone-hexane (1+1), and water-acetone-isooctane (5+1.5+1), recoveries of lower chlorinated congeners (dichloro- to tetrachloro-) were usually higher with acetonitrile and recoveries of higher chlorinated congeners (tetrachloro- to heptachloro-) extracted with acetone were superior (Dunnivant and Elzerman 1988). The completeness of extraction from a sample matrix does not seem to discriminate against specific isomers however, discrimination in the cleanup and fractionation process may occur and must be tested (Duinker et al. 1988b). 

On the other hand, noticeable cooperative preferential screw sense induction was reported in rodlike polysilane copolymers bearing (.S )-2-mcthylbutyl and 2-methylpropyl groups (10) and (R)-2-melhylbutyl and 2-methylpropyl groups (11) in isooctane (Chart 4.3). Since the UV-CD spectral features of the polysilane copolymers are almost identical with those of 4-6 and the Xmax varies sensitively with changes in the molar fraction of chiral substituents and temperature,28 the copolymer systems are suitable for testing the sergeants-and-soldiers phenomenon by their CD-UV spectra. 

TeGrotenhuis et al. [58] performed a 1 000 h stability test in a micro structured reactor for the steam reforming reaction with a catalyst not specified. A mixture of 74% isooctane, 20% xylene and 5% methylcyclohexane as simulated gasoline was fed to the reactor at a S/C ratio of three and a 650 °C reaction temperature. A regeneration step was performed after 500 h and finally the catalyst converted 97% of the feed. 

Scheme 10 A pair of rod-like dialkylpolysilanes (33-SS and 33-RR) undergoing helix-helix transition at - 65 °C in isooctane used for molecular parity test experiment...

A second amendment, Directive 97/48/EEC, laid down the conditions of use of volatile solvents, e g. isooctane and ethanol, as test liquids in the fat test . It provided that these solvents may replace olive oil or the other fat simulants (HB 307, sunflower oil, etc.) if the fat test is not applicable in its basic version for technical reasons or in routine checking. These conditions are shown in Tables 12-10 and 12-11. 

Test conditions with Test conditions with simulants D isooctane Test conditions with Test conditions with ethanol 95 % MPPO7 ... 

It is possible to carry out alternative tests using isooctane or ethanol or other solvents if the following conditions are satisfied ... 

The pattern of increasing conversion for equivalence ratios richer than the hydrocarbon breakthrough equivalence ratio appeared to depend on the fuel, however. Figure 3 provides a comparison of fuel nitrogen conversion from isooctane and toluene at the richest equivalence ratios tested in the JSC. For both fuels, HC s increased as the equivalence ratio was increased from 1.6 to 1.8. Corresponding increases in fuel nitrogen conversion were found for isooctane mixtures at 3, 6 and 10 ms residence times, but toluene mixtures at these conditions produced either smaller increases or decreases in conversion with increasing... 

A rating of the antiknock properties of a gasoline blend. Its octane number is the percentage of isooctane (2,2,4-trimethylpentane) in an isooctane/heptane blend that begins to knock at the same compression ratio as the gasoline being tested, (p. 97)... 

Residual Hexane (Note The isooctane, 2,2,4-trimethylpen-tane, used in this test should be of chromatographic-grade quality.)... 

Procedure Transfer an accurately measured volume of the Test Solution, equivalent to about 100 mg of a-tocopherol, into a separator, and add 200 mL of water. Extract first with 75 mL, then with two 25-mL portions of ether, and combine the ether extracts in another separator. Add 20 mL of a 10% solution of potassium ferricyanide in a 1 125 sodium hydroxide solution to the ether solution, and shake for 3 min. Wash the ether solution with four 50-mL portions of water, discard the washings, and dry over anhydrous sodium sulfate. Evaporate the dried ether solution on a water bath under reduced pressure or in an atmosphere of nitrogen until about 7 or 8 mL remain, and then complete the evaporation, removing the last traces of ether without the application of heat. Immediately dissolve the residue in 5.0 mL of isooctane, and determine the optical rotation. Calculate the optical rotation [see Optical (Specific) Rotation, Appendix IIB], using as c the concentration of D-a-Tocopheryl Acetate, as determined in the Assay (above), in 100 mL of solution. 

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