Magnesium placement

The most important characteristic of the magnesium oxide powder used in these cements is its reactivity (Glasson, 1963). Magnesium oxide needs to be calcined to reduce this, otherwise the cement pastes are too reactive to allow for placement. Surface area and crystal size are important and relate to the calcination temperature (Eubank, 1951 Harper, 1967 Sorrell Armstrong, 1976 Matkovic et ai, 1977). The lower reactivity of calcined magnesium oxide relates to a lower surface area and a larger crystallite size. 

Sodium softening is used to remove soluble hardness from water, including calcium, magnesium, barium, and strontium. As discussed in Chapter 8.1.6, sodium softeners are commonly used to pre-treat RO feed water to reduce the potential for scaling the membrane with hardness scales. In the next two sections, the placement of the sodium softener, either before or after the RO system, as well as the use of sodium softeners versus antisealants are discussed. 

The enzyme solution prepared from Pseudomonas aeruginosa 99 by Mitsuhashi and coworkers required magnesium ion, and had a substrate specificity similar to that of the enzyme solution prepared from Pseudomonas aeruginosa 130 as just described. The optimal pH was 6.5. These authors isolated the inactivated product of gentamicin Ci, and mass spectrometry thereof indicated an N-acetyl group present in the 2-deoxystreptamine moiety. The placement as a 3-N-acetyl group was shown by periodate oxidation of a methanolysis product, namely, iV-acetylgentamine, which consumes 2 moles of periodate per mole. 

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