H and Alkalinity

Elements with very low electronegativeties of approximately 1.0 see Electronegativity), form compounds in which the hydrogen appears as an anion, H. These compounds have many of the properties associated with ionic substances and are sometimes called ionic or saline hydrides. Ionic hydrides, formed with alkali (M+H ) and alkaline earth (M +H2 ) metals, are colorless crystalline solids that either melt or decompose at temperatures above 600 °C. All of the hydrides can be formed by direct combination of the elements at elevated temperatures ... 

Mixtures of amphoterics are not likely to be encountered, but a basic approach is outlined which will succeed in many cases. Acid-base titration is unlikely to be useful because of the presence of other weak acids and bases. The procedure therefore relies on titration with SDS and/or benzethonium chloride (BEC) and will not always be completely successful. In all cases, if two-phase titration fails, potentiometric titration is still likely to succeed. Acid solutions must be at least 0.1 M in H and alkaline solutions at least 0.1 M in OH . It may be possible to replace SDS with NaTPB in at least some cases. Sulphobetaines cannot be determined in the presence of other amphoterics without separation. 

PHB recovery from fed-batch cultured Alcaligenes latus, ATCC 29713, was examined by Tamer et al. using combinations of chemical and mechanical treatments to disrupt the cells. Chemical pretreatments used sodium chloride and sodium hydroxide. For salt pretreatment the cells were exposed to NaCl (8 kg m" ) and heat (60°C, 1 h), cooled to 4°C, and mechanically disrupted. For alkaline treatments, the cells were exposed to sodium hydroxide (0.025-0.8 kg NaOH per kg biomass) and mechanically disrupted at ambient temperature. A combined treatment with sodium chloride (8 kg m ), heat (60 °C, 1 h), and alkaline pH shock (pH 11.5, 1 min) was also tested. Mechanical disruption employed a continuous flow bead mill (2,800 rpm agitation... 

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