Deaerated solution

Corrosion resistance of stainless steel is reduced in deaerated solutions. This behavior is opposite to the behavior of iron, low-alloy steel, and most nonferrous metals in oxygenated waters. Stainless steels exhibit very low corrosion rates in oxidizing media until the solution oxidizing power becomes great enough to breach the protective oxide locally. The solution pH alone does not control attack (see Chap. 4, Underdeposit Corrosion ). The presence of chloride and other strong depassivating chemicals deteriorates corrosion resistance. 

Acidic attack on stainless steels differs from corrosion on nonsteunless steels in two important respects. First, nonoxidizing acid corrosion is usually more severe in deaerated solutions second, oxidizing acids attack stainless steel far less strongly than carbon steel. Hence, nitric acid solutions at low temperatures cause only superficial damage, but hydrochloric acid causes truly catastrophic damage. 

Broli, A. and Holtan, H., Use of Potentiokinetic Methods for the Determination of Characteristic Potentials for Pitting Corrosion of Aluminium in a Deaerated Solution of 3< o NaCl , Corros. Sci., 13, 237 (1973)... 

The kinetics and mechanism of the ketone-bisulfite addition were studied by the use of the polarographic technique (Rao Salunke, Reaction Kinetics and Catalysis Letters 26 273, 1984).The specific rate was found to depend on pH. For an equimolar solution of bisulfite and acetone in a deaerated solution of potassium hydrogen phthalate buffer containing potassium iodide as the... 

Figure 20 Cyclic voltammograms recorded at a platinum electrode in a MeCN solution of [Ir(triphos) (DBcat) J+ (a) deaerated solution (b) oxygenated solution. Scan rate 0.2 Vs. T= -20 °C... 

Figure 10.10. Frequency responses of intensity decays of possible oxygen sensors with various lifetimes. The arrows indicate the magnitude of changes in phase and modulation in the range from 0% oxygen (N2, deaerated solution) to about 20% oxygen (Air, equilibrium with air).

The predominant cathodic process for Cu corrosion will therefore be oxygen reduction in aerated solutions and hydrogen evolution in deaerated solutions. 

Electron transfer was mediated by metallic silver colloids whose surfaces contained either a strong (SH ) or a weak (CN ) nucleophile [531]. The former case is illustrated by changes in the absorption spectrum of a 1.0 x 10 4 M, deaerated solution of metallic silver particles, subsequent to the consecutive addition of 2.0 x 10 4 M NaSH and 3.0 x 10-4 M anthracene quinone sulfonic acid, AQS (Fig. 85) [506]. The origin of the intensity decrease and the broadening of the silver plasmon absorption band upon the addition of nucleophilic SH is incompletely understood. However, that an absorption... 

Photodecomposition accompanying directly excited delayed fluorescence will clearly be less obvious. For example, at the same rate of light absorption in a 5 X 10-SM solution of anthracene, and with the same quantum efficiency of photodecomposition, a period 1000 times as long would be required to produce the same percentage decomposition. It was in fact found that after prolonged irradiation, a deaerated solution of 5 X 10-BM anthracene was almost completely decomposed and a crystalline precipitate was formed which had the appearance of dianthracene. It seems not unlikely therefore that one or other of the excited dimers formed by triplet-triplet quenching may be partly converted into a stable dimer. If this is so, mixed triplet quenching should result in the formation of stable mixed dimers. Experiments are in hand to test these hypotheses. 

Tppts is a white solid which is slightly air sensitive. Deaerated solutions of tppts are stable if stored under inert gas atmosphere. The 31P NMR (161.8 MHz, D20) exhibits a singlet at 8 — 5.1 ppm. Detailed NMR data can be found in reference 19. Tppts is widely used as a ligand for metal-catalyzed reactions in water (e.g., hydrogenation, hydroformylation, carbonylation, and Heck reactions).1... 

The product analysis of L-ascorbic acid irradiated in deaerated solution is restricted to the measurement of dehydro-L-ascorbic acid, hydrogen, and the decrease in L-ascorbic acid.263 To account for the fact that N20 has no effect on G(L-ascorbic acid consumption), a rather complex mechanism has been put forward that also allows the formation of a reduction product (L-gulono-1,4-lactone, suggested but not measured). 

Figure 6. Hydrogen production at 25°C in deaerated solutions as a function of catalyst (rhodium) concentration during the first two hours of irradiation using 350 nm cut-off and water filters. Plotted are the amount of hydrogen produced in 25 ml DHP vesicle solution.and measured in the gas phase (16 ml) by GC s 2 x 10- J M DHP, 2 x 10 M CdS symmetrically distributed on both sides of the vesicles, and 10 J M PhSH as electron donor pH approximately 7 at sonication and during photolysis. Concentrations of the catalyst, reduced by uv irradiation prior to visible light photolysis ( - Dl 1 ° ...

In the presence of heptakis(6-bromo-6-deoxy-(3-CD) ((3-CD7Br), Femia and Cline Love observed the room-temperature phosphorescence of phenanthrene and other polynuclear aromatic hydrocarbons in N2-purged N,N-dimethylfol-mamide (DMF)-water mixtures [24], On the other hand, Hamai and Monobe observed room-temperature phosphorescence of 2-chloronaphthalene from a deaerated solution containing a 1 1 complex of 6-iodo-6-deoxy-(3-CD ((3-CDI) and 2-chloronaphthalene [25], This result indicates that even only one iodine atom on the (3-CD rim can accelerate the intersystem crossing rate of 2-chloronaphthalene included in the CD cavity. The room-temperature phosphorescence of 6-bromo-2-naphthol and 3-bromoquinoline was also observed for the complexes with (3-CDI [26],... 

Photolysis of Lignin Part 1. Deaerated Solutions of Dioxane-Lignin", Polymer Photochem., 1986, 7, 401. 

Table I shows that in either dioxane or acetonitrile the quantum yield for degradation of I, is unaffected by the presence of 0.1 M of triplet quencher, either sorbic acid, naphthalene or cyclohexadiene. In ethanol, triplet quenchers reduce < >d from 0.34 to 0.14. Quantum yields for intersystem crossing, as determined by a laser opto-acoustic technique ( ), were 0.36 in ethanol and 0.59 in dioxane. These results agree with our earlier report (3), and indicate that significant reactivity occurs from St of I in protic solvents, and that reaction occurs exclusively from Sx in aprotic solvents. While triplet quenching experiments cannot rigorously exclude participation by short-lived higher triplet states, Palm et al (9) have obtained conclusive evidence from CIDNP experiments for singlet-state participation in a series of aryloxy-acetophenones. Note that the triplet state of I is formed in aprotic solvents, and that in deaerated solutions at room temperature it decays by first-order kinetics with a lifetime of 200 ns (3). Remarkably, despite having lifetimes about 100 times longer than other, differently-substituted, aryloxyacetophenones (the longer lifetimes may...

Excitation of room temperature deaerated solutions of selected heterocyclic-substituted platinum-1,2-enedithiolates leads to a dual emission, which is characteristic of this class of molecules (Fig. 3) (17-19, 22-24, 29-31). As can be seen in Fig. 3, the triplet emission is diffusionally quenched by oxygen while the singlet emission is insensitive to oxygen. 

We shall assume that the solution is a good conductor and that conducting films are not preseut at the surface of contact. If we have a metal such as zinc in a deaerated solution of sulfuric acid where = 1 atmosphere, the following reactions are possible ... 

Abramson and King (22) found that etched Fe cylinders dissolved somewhat faster than cylinders which were polished with fine abrasive paper between runs. The following experiment with a Ni cylinder illustrates the effect of progressive roughening (23). A cylinder 1.9x2.52 cm, cut from a rolled anode bar, was rotated at U = 18, 000 cm /min in 400 ml of deaerated solution containing 1M HC1 and 0.05M FeClg. Weight losses in consecutive three-minute periods were ... 

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