Ethanol leaching

Amines react with salicylic aldehyde with the formation of a yellow Schiff s base, having Amax = 404 nm (reaction B). In toluene solvent, ether was needed to initiate the reaction. In a protic solvent, such as ethanol, the reaction proceeds readily. After calibration, the amine function thus allows the quantitative determination of the amount of an alkylamine or aminosilane liberated from a modified substrate upon ethanol leaching, by UV detection. 

Figure 9.17 Loss curves for short term ethanol leaching on APTS modified silica (x) uncured (+) 3h air cured ( ) 20h air cured ) 20h vacuum cured.

Figure 9.24 Ethanol leaching curves of uncured modified silica (a) APTS, (b) n-butylamine.

Both samples show a rapid initial loss. For APTS this is followed by a slow process. The APTS appears to have a largely increased stability compared to the butylamine. A tenfold relative amount of butylamine is released from the silica, over the measured time interval. A relative amount of respectively 78% and 9% is lost after 6 days of stirring in ethanol. This percentage is attributed to both hydrogen bonded and physically adsorbed molecules. Because both of these interaction types are expected to be unstable towards the ethanol leaching. 

The PGS obtained by Wang and coworkers was a kind of thermoset elastomer with the Young s modulus of 0.282 0.025 MPa, a tensile strain of at least 267 zE 59.4%, and a tensUe strength was at least 0.5 MPa. The mechanical properties of PGS were well consisted with that of some common soft tissues. Although PGS is a thermoset polymer, its prepolymer can be processed into various shapes by solving it in common organic solvents such as 1,3-dioxolane, tetrahydrofuran, isopropanol, ethanol, and iV,M-dimethylformamide. Porous scaffolds can be fabricated by salt leaching. 

In order to determine if inhibiting substances were present in soil in which tall fescue was growing, soil was dug from the field on March 20. Fescue roots were separated from the soil and saved along with leaves. Two hundred grams (fresh weight) each of fescue leaves and roots were leached overnight in 1,000 ml of ethanol and then filtered. Four hundred grams of the fescue soil was extracted... 

Sasson and Rempel [97] showed that the system [(PPh3)3RuCl2]/secondary alcohol is suitable for the selective transformation of 1,1,1,3-tetrachloro into 1,1,3-trichloro compounds. Similarly, Blum and coworkers [98, 99] employed [(PPh3)3RuCl2] as well as polystyrene-anchored Rh, Ru and Ir complexes for the hydrogen transfer from alcohols to trihalomethyl compounds, leading to dihalo-methyl derivatives. For example, one of the Cl atoms of 2,2,2-trichloro-l-phenyl-ethanol was displaced by H at 140-160 °C in 2-propanol. The polymer-anchored catalysts proved to be resistant to leaching [99]. 

Purification is often required for the beads obtained by the techniques described above since undesired substances such as surfactants, coupling agents, etc. need to be removed. This is also valid for dye molecules noncovalently adsorbed on the surface of the beads since they usually have different properties (sensitivity, cross-talk to other analytes, leaching, etc.) compared to the molecules located in the core. The dye-doped beads can be purified by repeated precipitation which is achieved by adding salts (typically sodium chloride). In certain cases (typically for large beads) the addition of salts is not necessary so that the beads can be isolated by centrifugation. Washing with ethanol often helps remove lipophilic dye molecules adsorbed on the surface provided that the polymer is not swellable. Alternatively, dialysis can be useful especially if a hydrophilic water-soluble indicator is covalently coupled to the bead surface. 

Despite the conflicting evidence, Heyes and Trahar (1984) believe there is sufficient evidence to confirm the presence of sulphur on mineral surface. They leached the surface of floated pyrrhotite from a typical test with cyclohexane and have examined the leach solution in a UV spectrophotometer. They found that sulphur could be extracted from the surface of pyrrhotite, which had been floated in the absence of collector. As can be seen from Fig. 2.26, the spectrum from the leached pyrrhotite was compared with the spectrum of sulphur dissolved in cyclohexane indicating that sulphur was present at the siuface. Kelebek and Smith (1989) used UV spectrophotometer to determine sulphur in the ethanol extract from the surface of floated galena and chalcopyrite showing that the amount of sulphur on the minerals can be correlated with their flotation rate which was found to be first order within the critical surface tension range. 

The sol-gel entrapment of the metal complexes [Ru(p-cymene)(BINAP)Cl]Cl and the rhodium complexes formed in situ from the reaction of [Rh(COD)Cl]2 with DlOP and BPPM has been reported by Avnir and coworkers [198]. The metal complexes were entrapped by two different methods the first involved addition of tetramethoxysilane to a THF solution of the metal complex and triethylamine, while the second method was a two-step process in which aqueous NH4OH was added to a solution of HCl, tetramethoxysilane and methanol at pH 1.96 followed by a THF solution of the appropriate metal complex. The gel obtained by each method was then dried, crushed, washed with boiling CH2CI2, sonicated in the same solvent and dried in vacuo at room temperature until constant weight was achieved. Hydrogenation of itaconic acid by these entrapped catalysts afforded near-quantitative yields of methylsuccinic acid with up to 78% e.e. In addition, the catalysts were found to be leach-proof in ethanol and other polar solvents, and could be recycled. 

In this paper, the selectivity of the ECH method for the reduction of nitro compounds to the corresponding amines on RCu electrodes will be compared with that of reduction by RCu alloy powder in alkaline aqueous ethanol. In the latter method (termed chemical catalytic hydrogenation (CCH)), chemisorbed hydrogen is generated in situ but by reduction of water by aluminium (by leaching of the alloy) (equation [12]). The reductions by in situ leaching must be carried out in a basic medium in order to ensure the conversion of insoluble Al(OH)3 into soluble aluminate (equation [12]). The selectivity and efficiency of the electrochemical reduction of 5-nitro-indoles, -benzofurane, and -benzothiophene at RCu electrodes in neutral and alkaline aqueous ethanol will also be compared with that of the classical reduction with zinc in acidic medium. 

Figure 2. Effect of purification on flocculation performance (O) unpurified (0) purified by leaching with ethanol (A) purified by ultrafiltration.

Santoprene extracts contained higher concentrations of inorganic carbon and little, if any, extractable silicon. On the other hand, the amount of silicone in extracts of silicone polymers was very high. From Table 37, it is possible to see that these materials, though all made of silicone, are very different each other. While about lOOpg/g Si was found in the aqueous extract from sample 1, no measurable Si was detected in the same extracts from samples 2 and 6. As could be expected, silicone extract-ables were much higher in ethanolic extracts, being that 739 pg/g Si from sample 6 was the lowest amount leached. 

Like methanol, the lubricating oil additive package should be tailored to be compatible with ethanol to prevent leaching of the additives from the oil. 

These results were further elaborated by measuring the silane loss over short leaching times for samples cured in air and under vacuum.35 Dehydrated mesoporous silica gel was modified with APTS or APDMS in dry toluene (1 % v/v silane/toluene). Curing was performed for variable times in air at 383 K or under vacuum at 423 K. For UV tests the modified silica was stirred in a salicylic aldehyde/ethanol solution. At indicated times a Sml sample was taken, centrifuged and the supernatant was measured at 404 nm. The loss curves of APTS for variably cured samples are displayed in figure 9.17. The position and profile of the absorbance curves are indicative for the stability of the coating under study. 

MTBE is currently synthesized industrially from methanol and isobutene over an acidic ion-exchange resin, mostly Amberlyst 15 which is in fact a macroreticular cation-exchange resin [1,2]. ETBE which is obtained by reaction of isobutene with ethanol, is also an attractive octane enhancer for gasoline [3]. Although the commercial catalyst is very efficient, it suffers from several drawbacks such as thermal instability, acid leaching from the resin... 

Some cases of catalyst deactivation by over-oxidation platinum leaching, platinum particle growth and site coverage during reductive pretreatment as well as during reaction were presented for the oxidation of ethanol and methyl-a-D glucopyranoside (MGP) in combination with the use of various catalyst characterization techniques. 

As a general rule, samples should be collected in decontaminated flasks and even those considered metal-free should be pre-washed. Glass recipients should be avoided. A good procedure for cleaning plastic containers is keeping them at least 24 h in a 10% (v/v) ethanolic nitric acid solution. Aqueous solutions do not leach out the aluminum well, because water does not wet plastic surfaces better contact occurs when an alcoholic solution is used. It can be seen that all alcoholic solutions were more efficient than the aqueous solutions. Table 10 shows the aluminum extracted from polyethylene by the action of some washing solutions. Just before use, the containers should be abundantly washed with ultrapure water. The best option is to use the flasks just after rinsing them, however if they must be dried, they should not be placed in an oven, even with the open side on tissue paper (paper contains aluminum). The best way is let them dry under a laminar flow. The proper heat and air movement inside the hood will help to rapidly dry the flasks. 

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