Toluene sampling

Purity of toluene samples as well as the number, concentration, and identity of other components can be readily determined using standard gas chromatography techniques (40—42). Toluene content of high purity samples can also be accurately measured by freezing point, as outlined in ASTM D1016. Toluene exhibits characteristic uv, it, nmr, and mass spectra, which are useful in many specific control and analytical problems (2,43—45). 

FIQURE 5-4.5.2. Effect of added methyl ethyl ketone on eonduetiuity of a toluene sample. 

Samples were either prepared by direct addition of polymer to solvent (Method I) or by a careful method to reduce dust (Method II) In Method II, PBLG was added from a stock solution in distilled DMF via a 0 2ym filter (Millipore type FG) into preweighed cells that had been exhaustively rinsed with nearly dust-free water from a Millipore 4 stage purifier and dried Under vacuum, the samples were either concentrated or evaporated to dryness, depending respectively on whether a PBLG/DMF or PBLG/toluene sample was desired For... 

PBLG/toluene samples, toluene was added by weight via a 0.05im filter (Millipore type VM). The samples were then flame-sealed and homogenized by slow tumbling at room temperature (DMF) or 100 C (toluene). 

Figure 6. Toluene sampling data T = 298 K RH = < 5% P = 760 mm Hg concentration — 125 ppm ( ) front section (O) backup section...

Purity of toluene samples as well as the number, concentration, and identity of other components can be readily determined using standard gas chromatography techniques. 

Figure 1 shows kinetic curved lines of A1H3 decomposition. As can be seen from figure, the most stable A1H3 were synthesized during interaction of LiAlH4 solution with solutions of HC1 + toluene (samples 10, 22)... 

By using a newer instrument equipped with a superconducting magnet and the same toluene sample as before, we can generate the 250-MHz H spectrum of toluene shown in Figure 5.3. In this figure, only the 8 scale is shown. 

Radioisotope Procedures. Radioactive volatile acids separated by Wiseman-Irvin chromatography were collected in 1 ml of 0.5N KOH. The aqueous fraction containing the acid was transferred to a scintillation vial and evaporated to dryness in a vacuum oven at 20 psi and 50 °C. The residue was redissolved in 0.1 ml distilled H2O before adding 4 ml of absolute ethanol and 15 ml of scintillation fluid 2,5-diphenyloxazole (PPO) and 0.01% 1,4-bis[2-(5-phenyloxazolyl)]benzene (POPOP) in toluene. Samples were counted in a liquid scintillation counter (Nuclear Chicago Corp.). 

Toluene-dioxane-based PPO, POPOP, naphthalene in dioxane-toluene. Sample is prepared in a base such as hyamine hydroxide. 

The second equilibration resulted in a small n-hexane peak, a small cyclohexane peak, and a toluene peak reduced by approximately 20%. A small benzene peak exists as an impurity from the toluene sample. The third equilibration shows no n-hexane peak, a very small cyclohexane peak, a small benzene peak, and toluene as the major hydrocarbon remaining. 

The amount of mercury in the syringe should be proportional to the concentration of mercury in the liquid phase, if equilibrium was established. While the toluene sample was constructed at a lower concentration (14.5 pg/kg) than the US19-C12/Hg sample (124 pg/kg), it consistently provided more mercury to the vapor phase. This demonstrates the effect of liquid phase composition on mercury volatility. It is not known if complete equilibrium was established between mercury in the vapor and liquid phase, but the qualitative trends are apparent. Volatile mercury partitions to the vapor space of sample containers at a significant rate. 

All these samples, except No. 7, were powders of 5-7 /n grain size, which had been elutriated in toluene. Sample 7 was prepared by simple grinding in an agate mortar (this sample was used simply to check the presence of a second phase in a method for growing stoichiometric crystals from a melt which was enriched with mercury in order to establish an equilibrium vapor pressure durii growth). 

A plot of these data, if desired, give the familiar water sample quenching curve for the solgel scintillator. The phase contact ratio for each concentration is then calculated by dividing the relative counting efficiency for tritiated water at each concentration by the relative counting efficiency for the tritium-labeled toluene sample at the Scime concentration ... 

The errors resulting from the addition of distilled water to reach the various concentrations should be negli-bible if done with care. For example, to reach a concentration of exactly 10% by volume, 1.022 mL of water should be added. In order to avoid the errors resulting from attempting to extrapolate between divisions, a volume of 1.05 itiL is used which results in a true concentration of 10.22% by volume. This is designated at the 10% sample. Since exactly the same volume is used on the tritiated water as on the comparable tritiated toluene sample, the final concentrations are the same in each vial and the errors cancel. Adding quantities of water that are measurable exactly on burette calibration marks tremendously improves the ability to add equal amounts to comparable vials. 

Figure 7. The storage modulus at

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