Measuring Water Compatibility

The tendency of water to form scale or cause corrosion is measured by either the Langelier Scaling Index (LSI), which is also called the Saturation Index, or the Ryznar Stability Index (RSI), which is also called the Stability Index (Table 4.2). 

Total solids scale. Proceed horizontally to the right diagonal line down to the pAlk scale. Locate ppm value for total solids on the ppm scale. 

Example Temp. = 140 °F, Proceed horizontally to the proper temperature line and up to the C scale. pCa = 2.70 

FIGURE 4.4. Langelier Saturation Index Chart (reprinted from GPSA Engineering Data Book, courtesy of Betz Laboratories, bic.). 

When the index is less than 6, scahng can be expected an index between 6 and 7 indicates a stable water. A pH greater than 7 indicates potential corrosion problems. 

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A comparison of literature values of subzero collapse transition temperatures (Tc) for an extensive list of water-compatible monomers and polymers has established the fundamental identity of Tg with the minimum onset temperatures observed for various structural collapse and recrystallization processes (1.2.115), for both model solutions and real systems of foods, as well as pharmaceuticals and biologicals (38.42.106.108.109). The Tc and Tr values of frozen or vitrified samples, tabulated elsewhere (1.2.22). are typically determined by cryomicroscopy, thermal analysis, or electrical resistance measurements (22 and refs, therein), on an experimental time scale similar to that for Tg by our DSC method (106.109). A comprehensive list of collapse processes (Table I), all of which are governed by Tg of frozen systems (or a higher Tg pertaining to low moisture systems processed or stored at T > 0 C) and involve potentially detrimental plasticization by water, has been identified and elucidated (1-5.18-... 

Lanthanum is the first element of the sixth-period transition metals. Its properties are close to those of the other rare earth elements and, as a consequence, the catalytic behavior of the lanthanum triflate is also very close to that of the entire series. An important example concerning the stability of these compounds in water is that indicating the capability of metal triflates, such as Yb(OTf)3, Eu(OTf)3, Sc(OTf)3 or La(OTf)3, to catalyze the hydration of alkynes to the corresponding ketones [56]. However, the interest in water-compatible lanthanide triflate-based catalysts is much larger and mainly includes the carbon-carbon bond-forming reactions. To increase the utility of these catalysts understanding of their aqueous mechanism is very important. For such a purpose, dynamic measurements of the water... 

An ELSD converts the HPLC eluent into a particle stream and measures the scattered radiation. It offers universal detection for nonvolatile or semivolatile compounds and has higher sensitivity than the RI detector (in the low ng range) in addition to being compatible with gradient analysis. ELSD is routinely used in combinatorial screening. Response factors are less variable than that of other detectors. An ELSD consists of a nebulizer equipped with a constant temperature drift tube where a counter-current of heated air or nitrogen reduces the HPLC eluent into a fine stream of analyte particles. A laser or a polychromatic beam intersects the particle stream, and the scattered radiation is amplified by a photomultiplier. Manufacturers include Alltech, Polymer Laboratories, Shimadzu, Waters, Sedere, and ESA. 

Cosmetic Rinse off Preparations. In certain cosmetic products, tor example hair shampoos, it is not possible to use complexing agents because of the irritation of mucous membranes. Here a low sensitivity of surfactants to water hardness is a precondition for their application. Foam formation is generally considered to be a measure of shampoo quality (Table V). With increase in water hardness the foam volume of alkyl sulfates decreases very much, whereas with the corresponding alkyl ether sulfates this decrease is relatively small. For cosmetic applications, the good skin compatibility and low irritation to mucous membranes of alkyl ether sulfates is of high importance (37). 

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