Oxides of Ga, In and

ThaUium(III) forms the oxide TI2O3, but no simple hydroxide. TI2O3 is insoluble in water and decomposes in acids. In concentrated NaOH solution and in the presence of Ba(OH)2, the hydrated oxide Tl203-xH20 forms 

Ba2[Tl(OH)6]OH. In the solid state, the [Tl(OH)g] ions are connected to Ba and [OH] irais to give a structure that is related to that of K2PtCIfi (see Section 22.11). 

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Hydrous aluminum oxide is used frequently in chromatographic columns. Hydrous oxides of Ga, In, and the lanthanides may also be employed as inorganic ion exchangers. However, substantive research of these oxides has not been performed. 

The binary oxides and hydroxides of Ga, In and T1 have been much less extensively studied. The Ga system is somewhat similar to the Al system and a diagram summarizing the transformations in the systems is in Fig. 7.13. In general the a- and y-series have the same structure as their Al counterparts. )3-Ga203 is the most stable crystalline modification (mp 1740°) it has a unique crystal structure with the oxide ions in distorted ccp and Ga " in distorted tetrahedral and octahedral sites. The structure appears to owe its stability to these distortions and, because of the lower coordination of half the Ga ", the density is 10% less than for the a-(corundum-type) form. This preference of Ga "... 

Construct Frost-Ebsworth diagrams for Ga, In and T1 at pH = 0. Use the diagrams to comment on (a) the relative abilities of Ga +, In + and Tl to act as oxidizing agents under these conditions, and (b) the relative stabilities of the +1 oxidation state of each element. 

Method 1. From ammonium chloroplatinate. Place 3 0 g. of ammonium chloroplatinate and 30 g. of A.R. sodium nitrate (1) in Pyrex beaker or porcelain casserole and heat gently at first until the rapid evolution of gas slackens, and then more strongly until a temperature of about 300° is reached. This operation occupies about 15 minutes, and there is no spattering. Maintain the fluid mass at 500-530° for 30 minutes, and allow the mixture to cool. Treat the sohd mass with 50 ml. of water. The brown precipitate of platinum oxide (PtOj.HjO) settles to the bottom. Wash it once or twice by decantation, filter througha hardened filter paper on a Gooch crucible, and wash on the filter until practically free from nitrates. Stop the washing process immediately the precipitate tends to become colloidal (2) traces of sodium nitrate do not affect the efficiency of the catalyst. Dry the oxide in a desiccator, and weigh out portions of the dried material as required. 

Since 1960, the Hquid-phase oxidation of ethylene has been the process of choice for the manufacture of acetaldehyde. There is, however, stiU some commercial production by the partial oxidation of ethyl alcohol and hydration of acetylene. The economics of the various processes are strongly dependent on the prices of the feedstocks. Acetaldehyde is also formed as a coproduct in the high temperature oxidation of butane. A more recently developed rhodium catalyzed process produces acetaldehyde from synthesis gas as a coproduct with ethyl alcohol and acetic acid (83—94). 

Fig. 9. Genesis of acid tain (13). From the oxidation of C, S, and N during the combustion of fossil fuels, there is a buildup in the atmosphere (gas phase, aerosol particles, raindrops, snowflakes, and fog) of CO2 and the oxides of S and N, which leads to acid—base interaction. The importance of absorption of gases into the various phases of gas, aerosol, and atmospheric water depends on a number of factors. The genesis of acid rain is shown on the upper right as an acid—base titration. The data given are representative of the environment in the vicinity of Zurich, Switzedand.

Ammonium chloroplatinate often can be used to advantage in place of chloroplatim c acid in the preparation of Adams catalyst. A mixture of 3 g. of ammonium chloroplatinate and 30 g. of sodium nitrate in a casserole or Pyrex beaker is heated gently at first until the rapid evolution of gas slackens and then more strongly until a temperature of 500° is reached. This operation requires about fifteen minutes and there is no spattering. The temperature is held at 500-520° for one-half hour and the mixture is then allowed to cool. The platinum oxide catalyst, collected in the usual way by extracting the soluble salts with water, weighs 1.5 g. and it is comparable in appearance and in activity to the material prepared from chloroplatinic acid. 

The poor solubility of coelenterazine in neutral aqueous buffer solutions often hampers the use of this compound in biological applications. The simplest way to make an aqueous solution is the dilution of a methanolic 3 mM coelenterazine with a large volume of a desired aqueous buffer solution. If the use of alcoholic solvents is not permitted, dissolve coelenterazine in a small amount of water with the help of a trace amount of 1 M NaOH or NH4OH, and then immediately dilute this solution with a desired aqueous buffer solution. However, because of the rapid oxidation of coelenterazine in alkaline solutions, it is recommended that the procedure be carried out under argon gas and as quickly as possible. 

Carbon monoxide (CO) is a colorless and odorless gas molecule. This inorganic compound, at standard temperature and pressure, is chemically stable with low solubility in water but high solubility in alcohol and benzene. Incomplete oxidation of carbon in combustion is the major source of environmental production of CO. When it burns, CO yields a violet flame. The specific gravity of CO is 0.96716 with a boiling point of -190°C and a solidification point of-207°C. The specific volume of CO is 13.8 cu ft/lb (70°F). 

Epoxides such as ethylene oxide and higher olefin oxides may be produced by the catalytic oxidation of olefins in gas-liquid-particle operations of the slurry type (S7). The finely divided catalyst (for example, silver oxide on silica gel carrier) is suspended in a chemically inactive liquid, such as dibutyl-phthalate. The liquid functions as a heat sink and a heat-transfer medium, as in the three-phase Fischer-Tropsch processes. It is claimed that the process, because of the superior heat-transfer properties of the slurry reactor, may be operated at high olefin concentrations in the gaseous process stream without loss with respect to yield and selectivity, and that propylene oxide and higher... 

Consequently, the antioxidant activity of GA in biological systems is still an unresolved issue, and therefore it requires a more direct knowledge of the antioxidant capacity of GA that can be obtained by in vitro experiments against different types of oxidant species. The total antioxidant activity of a compound or substance is associated with several processes that include the scavenging of free radical species (eg. HO, ROO ), ability to quench reactive excited states (triplet excited states and/ or oxygen singlet molecular 1O2), and/or sequester of metal ions (Fe2+, Cu2+) to avoid the formation of HO by Fenton type reactions. In the following sections, we will discuss the in vitro antioxidant capacity of GA for some of these processes. 

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