And water hardness

FIG. 8 Effect of chain length of a-ester sulfonates and water hardness on detergency R for fabrics soiled with clay/sebum (T = 60°C 1 g/L surfactant). (From Ref. 58.)... 

Conductivity sensors are most commonly used for safety purposes in household appliances. Presence and absence of washing liquor, detergency, and water softener can be easily measured and proper operation ensured [71]. The various applications mainly differ by their design of electrode geometry and methods for electrical measurement. Due to the close relation between ionic conductivity and water hardness, the automatic water softener in an automatic dishwasher can be controlled by a conductivity sensor [72]. To isolate the transmission of the measured value from the process controller, the conductivity sensor could incorporate an opto-electronical coupling [73]. Thus, protective insulation of the electrodes in a washer-dryer could be ensured. 

Penttinen, S., A. Kostamo, and J.V.K. Kukkonen. 1998. Combined effects of dissolved organic material and water hardness on toxicity of cadmium to Daphnia magna. Environ. Toxicol. Chem. 17 2498-2503. 

Pagenkopf, G. K. (1983). Gill surface interaction model for trace-metal toxicity to fishes role of complexation, pH, and water hardness, Environ. Sci. Technol., 17, 342-347. 

Table 17.8 gives an overview of experimentally determined values of KqW. An increase of log Kow occurs with increasing carbon chain length. For LAS, this increase is 0.33 log units per C-atom and is unaffected by LAS concentration and water hardness (Kimerle et al., 1975). However, log Kow of C12-LAS varies by two orders of magnitude, depending on the concentration of the surfactant and the electrolyte. 

Matheson, K.L., M.F. Cox, and D.L. Smith. 1985. Interactions between linear akylbenzene sulfonates and water hardness ions. I. Effect of calcium ion of surfactant solubility and implications for detergency performance. JAOCS 62, 1391-1399. 

Martins, J.E., Pardo, R., and Boaventura, R.A.R. 2004. Cadmium (II) and zinc (II) adsorption by the aquatic moss Fontinalis antipyretica effect of temperature, pH and water hardness. Water Research, 38 693-9. 

These are useful insights, but they should be kept in perspective. This particular study did not take into account other important variables such as temperature and water hardness. The effects produced by these other independent variables can be handled separately in other studies, and their respective contour maps generated. These could also be used as factors in calculating the "Performance" variable. 

Powerful nonionic surfactant combining excellent wetting properties with detergency and emulsifying ability over a broad range of pH and water hardness conditions. 

In general terms, toxicity tests are conducted in a laboratory or a room controlled for light and temperature. The test solutions containing the test species are monitored for pH, temperature, dissolved oxygen, and water hardness. Daily observations on lethal and... 

Known and proven influences include temperature, pH and water hardness. 

Winner, R. W. (1985). Bioaccumulation and toxicity of copper as affected by interactions between humic acid and water hardness. Water Res. 19, 449-455. 

Some important automated instruments based on ion-selective electrodes measure sodium in boiler feedwaters, fluoride in public water-supplies, and water hardness (Ca " and Mg +) in water-conditioning systems. The sulfide electrode is extensively used in the paper industry for monitoring and control of sulfidity in paper pulping liquors (for instance, the Kraft process), for waste-treatment control of excess sulfide using a process that oxidizes sulfide with air, and for monitoring... 

Also pH and water hardness can influence the viscosity of depositable material as the fatty acids may be converted into calcium soaps or other soaps of divalent and trivalent ions. Increase in pH (up to approximately pH 9.0) and increasing water hardness will increase the formation of metal soaps of fatty acid. The formation of metal soaps of fatty acid will increase the viscosity of the organic material. 

The LC50 values determined for chloroform in tests with embryos and larvae of the rainbow trout were 2.03 and 1.24 mg/liter in soft and hard water, respectively. The LC, values were 6.2 and 4.9 /xg/liter, and water hardness was not a significant factor. Reproductive tolerance to chloroform obviously varies widely for different aquatic species. However, on the basis of the above data, it is... 

Fignre 6 provides another clear example of the interaction between otherwise harmless water qnahty characteristics and toxicant effects. The toxicity of zinc to rainbow front is clearly correlated in a negative way with water hardness. Similar correlations between metal toxicity and water hardness have been noted for a variety of toxic metals. The mechanism responsible for the correlation is not well understood, and considering the wide range of metals for which the effect has been observed, it is unlikely that exactly the same mechanism is operative in all cases. Water hardness, which is a measnre of the concentration of calcium and magnesium ions in the water, tends to be correlated with a number of other water quality characteristics such as pH and alkalinity. Therefore it is possible that at least in some cases the observed negative correlation between metal toxicity and water hardness actually reflects a cause-and-eflfect relationship with one of these other covariates. 

For the hypochlorite that is produced on-site when needed, metals may not be a problem. For other uses, venting containers for storage and transportation may be sufficient Steps can also be taken to avoid metals. Municipal water may be treated by ion exchange to remove transition metals and water hardness. Sodium hydroxide can be used directly from mercury or membrane cells without evaporation, or it can be treated to reduce metals as described in Section 24.2.3. Titanium or nonmetallic equipment, tanks, and piping can be used to avoid contact with offensive metals. However, additional purification is usually required to package hypochlorite solutions in nonventing bottles or pouches and to maximize shelf life. 

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