Stirring methods

The stirbar is normally placed in the flask or vial before any other materials, such as solvents or reagents. In the case of introducing stirbars into a flask, you should not simply drop the stirbar into the flask, because you might crack or break it. Rather, tilt the flask and let the stirbar gently slide down the side. 

A flat-bottom container such as a beaker or Erlenmeyer flask may be placed directly on top of the stirrer (Fig. 2.34a), whereas a round-bottom flask or a conical 

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Very recently, a dry-stir method for the mechanical activation of commercial magnesium turnings was reported16. The procedure is also excellently suited for the preparation of allylic and benzylic Grignard reagents (Table 1, method B). 

FIG. 6 Measurements of the interfacial adsorptivity and the extraction rate from the absorbance changes of the organic phase by means of the high-speed stirring method, (a) Heptane-water system... 

De Bruijn, J., Busser, G., Seinen, W., Hermens, J. (1989) Determination of octanol/water partition coefficient for hydrophobic organic chemicals with the slow-stirring method. Environ. Toxicol. Chem. 8, 499-512. 

HPLC-k correlation ODS column Diol column quoted lit. average, Helweg et al. 1997) 3.33 (range 3.24-3.40) (slow stirring method-HPLC/fluo., De Maagd et al. 1998)... 

In refluxing acetonitrile the activities of catalysts 57-60 were 60 > 59 > 58 > 57, while in refluxing dioxane 60 > 57 > 58 = 59. However, the reactions were very slow. In dioxane only the soluble 18-crown-6 ether (60) gave a yield of benzyl acetate of more than 31 % in 2 days. Details of catalyst and potasium acetate particle size and stirring method were not reported l82). The higher activity of the solid catalyst 57 than of the soluble analog 58 is highly unusual because mass transfer and intra-... 

Mass exchange between a non-aqueous-phase liquid (NAPL) such as diesel fuel and water can be studied with the so-called slow stirring method (SSM). The SSM was designed to determine solubilities and octanol-water partition coefficients of organic compounds such as petroleum hydrocarbons. The kinetics of the exchange process also yield valuable information on the exchange between ground-water and a NAPL spilled into an aquifer. 

Figure 19.12 (a) Experimental setup to determine the exchange dynamics of a combined NAPL-water system using the slow stirring method (SSM). (6) - (d) Measured and calculated aqueous concentrations of benzene m/p-xylene and naphthalene. The solid lines give the result of the linear bottleneck exchange model with an aqueous boundary layer thickness of 8bl = 2.4 x 1CT2 cm = 240 pm (adapted from Schluep et al., 2000). 

Dependence on Temperature For most compounds, values of Kow have been determined at temperatures between 20 and 25°C. The effect of temperature on Kovl is small, usually lower than 0.02 logio Kow unit per degree. For example, log Kow of 1,2,3,4-chlorobenzene has been determined with the slow stirring method as 4.635 0.004 at 25°C [9] and as 4.564 0.074 at 29°C [8]. 

Magnetic stirrer and stir bar (or other stirring method)... 

Fisk, A T., Bosenberg, B., Cymbalisty, C.D, Stem, G.A., Muir, D.C.G. (1999) Octanol/water partition coefficients of toxaphene congeners determined by the slow-stirring method. Chemosphere 39, 2549-2562 Fisk, AT., Norstrom, R.J., Cymbalisty, C.D, Muir, D.C.G. (1998) Dietary accumulation and depuration of hydrophobic oiganochlo-rines bioaccumulation parameters and their relationship with the octanol/water partition coefficient. Environ. Toxicol. Chem. 17, 951-961. 

Fisk, A.T., Bosenberg, B., Cymbalisty, C.D., Stem, G.A., Muir, D.C.G. (1999) Octanol/water partition coefficients of toxaphene congeners determined by the slow-stirring method. Chemophere 39, 2549-2562. 

Sijm, D.T.H.M., Wever, H., de Vries, P.J., Opperhuizen, A. (1989a) Octan-l-ol/water partition coefficients of polychlorinated dibenzo-p-dioxins and dibenzofurans experimental values determined with a stirring method. Chemosphere 19, 263-266. 

RP-HPLC correlation, McDuffie 1981) (22°C, shake flask-GC, Bowman Sans 1983b) (shake flask-GC, Schimmel et al. 1983) (HPLC-RT correlation, De Kock Lord 1987) (HPLC-RT correlation, Liu Qian 1988) (shake flask/slow-stirring method, De Bruijn et al. 1989) (Worthing Hance 1991 Tomlin 1994 Milne 1995) (Montgomery 1993) (RP-HPLC, Saito et al. 1993) (RP-HPLC-RT correlation, Sicbaldi Finizio 1993) (recommended, Sangster 1993) (shake flask-HPLC, Ankley et al. 1994) (recommended, Hansch et al. 1995) (RP-HPLC-RT correlation using short ODP column, Donovan Pescatore 2002) (literature-derived value LDV, Muir et al. 2004)... 

DDE, shake flask/slow stirring method, De Bruijn et al. 1989 received highest ranking from... 

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