Mass oxide/hydroxide ions

The equivalent is defined in terms of a chemical reaction. It is defined in one of two different ways, depending on whether an oxidation-reduction reaction or an acid-base reaction is under discussion. For an oxidation-reduction reaction, an equivalent is the quantity of a substance that will react with or yield 1 mol of electrons. For an acid-base reaction, an equivalent is the quantity of a substance that will react with or yield 1 mol of hydrogen ions or hydroxide ions. Note that the equivalent is defined in terms of a reaction, not merely in terms of a formula. Thus, the same mass of the same compound undergoing different reactions can correspond to different numbers of equivalents. The ability to determine the number of equivalents per mole is the key to calculations in this chapter. 

Monoxide (MO+) and hydroxide (MOH+) ions, where M can be any one of many elements, are observed in ICP-MS [140], Typically the molecular oxide or molecular hydroxide signals are small (<3%) relative to the elemental ion signal. However, if one is trying to measure a small concentration of one element in the presence of a high concentration of a second element that forms a molecular oxide or hydroxide ion at the same mass as an analyte, the problem can be severe. Furthermore, the molecular ions may overlap with an elemental ion isotope that is... 

Among the commonly observed spectral overlap problems due to molecular oxide and molecular hydroxide ions are those due to TiO+ (with 5 isotopes of Ti from mass 46 to 50) that result in overlaps with a minor isotope of nickel, 62Ni+ both isotopes of copper, 63Cu+ and 65Cu + and the two major isotopes of zinc, MZn+ and 66Zn+. Calcium oxide and hydroxide ions overlap with all five isotopes of nickel, both isotopes of zinc, and three of the four isotopes of iron. The analysis of rare earth elements is particularly complicated by molecular oxide and hydroxide ion spectral overlaps [141,142]. 

This hydrolysis proceeds slowly at temperatures just below 100°C, and 1 to 2 hours is needed to complete a typical precipitation. Urea is particularly valuable for the precipitation of hydrous oxides or basic salts. For example, hydrous oxides of iron(III) and aluminum, formed by direct addition of base, are bulky and gelatinous masses that are heavily contaminated and difficult to filter. In contrast, when these same products are produced by homogeneous generation of hydroxide ion, they are dense and easily filtered and have considerably higher purity. Figure 12-5 shows hydrous oxide precipitates of aluminum formed by direct addition of base and by homogeneous precipitates with urea. Homogeneous precipitation of crystalline precipitates also results in marked increases in crystal size as well as improvements in purity. 

The pH s adjusted in both solutions to prevent any silver oxide from precipitating, and the protons and hydroxide ions are assumed to play only a minor role in the mass transport. 

Minnich, M.G. and Houk, R.S. (1998) Comparison of cryogenic and membrane desolvation for attenuation of oxide, hydride and hydroxide ions and ions containing chlorine in inductively coupled plasma mass spectrometry. J. Anal. At. Spectrom., 13, 167-174. 

To explain the effect of water on the location of chlorine at the surface of the catalyst, a combined time-of-flight-secondary ion mass spectrometry and X-ray photoelectron spectroscopy study has been carried out fresh and used LaMn03+5 catalysts [60]. Both techniques indicated that the presence of chlorine on the tested catalysts increased by exposure of the catalyst to the reactive mixture in dry synthetic air. Chlorine was present as both chloride ion and covalent chlorine on perovskite, while organic chlorinated residues were absent. The lanthanum excess as oxide (hydroxide) partially covering the perovskite mainly transforms into LaOCl and to a minor extent into Lads. Water delays the surface degradation extent of the perovskite into related (oxy) (hydroxy) chlorinated inorganic phases by less molecular chlorine and related chlorine species on the catalyst surface. Equations (17.4)-(17.6) describe the reaction scheme of Cl removal over the investigated perovskite and the role of water. 

Hydrated Stannic Oxide. Hydrated stannic oxide of variable water content is obtained by the hydrolysis of stannates. Acidification of a sodium stannate solution precipitates the hydrate as a flocculent white mass. The colloidal solution, which is obtained by washing the mass free of water-soluble ions and peptization with potassium hydroxide, is stable below 50°C and forms the basis for the patented Tin Sol process for replenishing tin in staimate tin-plating baths. A similar type of solution (Staimasol A and B) is prepared by the direct electrolysis of concentrated potassium staimate solutions (26). 

To prepare colloid iron(III) hydroxide, heat 200 mL of distilled water in a beaker to 70°-90°C and leave an identical beaker of water at room temperature. Add 1 mL of 1 M FeCl3 to each beaker and stir. The warm solution turns brown-red in a few seconds, whereas the cold solution remains yellow (Color Plate 31). The yellow color is characteristic of low-molecular-mass Fe3+ compounds. The red color results from colloidal aggregates of Fe3+ ions held together by hydroxide, oxide, and some chloride ions. These particles have a molecular mass of 105 and a diameter of 10 nm, and they contain 103 atoms of Fe. 

In most of its ionic compounds, cobalt is either Co(II) or Co(III). One such compound, containing chloride ion and waters of hydration, was analyzed, and the following results were obtained. A 0.256-g sample of the compound was dissolved in water, and excess silver nitrate was added. The silver chloride was filtered, dried, and weighed, and it had a mass of 0.308 g. A second sample of 0.416 g of the compound was dissolved in water, and an excess of sodium hydroxide was added. The hydroxide salt was filtered and heated in a flame, forming cobalt(III) oxide. The mass of the cobalt(III) oxide formed was 0.145 g. 

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