Precipitant effect

In addition to monomers and the initiator, an inert liquid (diluent) must be added to the monomer phase to influence the pore structure and swelling behavior of the beaded resin. The monomer diluent is usually a hydrophobic liquid such as toluene, heptane, or pentanol. It is noteworthy that the namre and the percentage of the monomer diluent also influence the rate of polymerization. This may be mainly a concentration or precipitation effect, depending on whether the diluent is a solvent or precipitant for the polymer. For example, when the diluent is a good solvent such as toluene to polystyrene, the polymerizations proceed at a correspondingly slow rate, whereas with a nonsolvent such as pentanol to polystyrene the opposite is true. 

Cormie, A.B. and Schwarcz, H.P 1996 Effects of climate on deer bone 5 N and 5 C lack of precipitation effects on 8 N for animals consuming low amounts of C, plants. Geochimica et Cosmochimica Acta (T)-. 4161 166. 

Calcium tartronate was precipitated and hence samples required acidification prior to the filtration step necessary to remove the catalyst. The chief product of over-oxidation was oxalic acid. However, conversion to oxalic acid proceeds at a relatively low rate and yields of the former are consequently high. This is probably partly due to the tartronate being precipitated, effectively hindering further oxidation. 

Co-precipitation effects do not give a real composition of the precipitate, and... 

When the salt concentration is high enough (> 0.1 M) some of the salt will precipitate in proportion as the cosolvent concentration is increased and the temperature of the mixture decreased. While in such conditions the precipitating effect of the cosolvent toward proteins will increase (Edsall, 1947 Singer, 1962) and a new equilibrium of ions between the crystals (/ ") and the bulk solvent medium (/" ) will be established, modifying both the Donnan and electrostatic terms. In the presence of salt (say sodium chloride), the distribution of the hydrogen ions is correlated with that of the chloride ions by the Donnan relationship ... 

This small increase in attachment to the cells after 1 day was likely because the iron level in culture decreased with time as a result of the metabolic production of sulhde, which complexed with the iron to produce the iron sulfide precipitate, effectively lowering the dissolved iron concentration toward that of the low iron condition. It would seem that when organisms are placed in low-iron environments, they will use their chemotactic response/biologic inductions mechanisms to ensure that the iron requirements of the cells high iron requiring proteins (i.e., cytochromes, ferre-doxin, hydrogenases) are satished. 

For the precipitation effects, acid dyes with little affinity to the fiber are rendered sparingly soluble (e.g., precipitated with alum) or are bound to the cellulose fiber with a polymer, generally a cationic fixative. 

Hofmeister, F. (1888). On the understanding of the effect of salts. Second report. On regularities in the precipitating effects of salts and their relationship to their physiological behavior. Naunyn-Schmiedebergs Arch. Exper. Path. Pharmakol. (Leipzig) 24 247-260. 

Commonly, different metals exhibit different solution pH of zero net charge. For this reason, different metals exhibit minimum solubility at different pH values, which makes it difficult to precipitate effectively two or more metals, as metal-hydroxides, simultaneously. Thus metal-hydroxide solubility as a function of pH displays a U-shaped behavior. The lowest point in the U-shaped figure signifies the solution pH of zero net charge and is demonstrated below. Consider the solid Fe(OH)2s,... 

Sulfide produces an undesirable rotten-egg odor and is toxic when in the HjS gas form. Since the first pKa of H2S is 7.24, it is necessary to maintain pH 9 or above to completely prevent evolution of H2S gas (Fig. 12.7). Although excess H2S is necessary for the precipitation reaction, the excess must be kept to a minimum. Furthermore, although metal-sulfide solubility with respect to pH exhibits U-shaped behavior (Fig. 12.8), its solubility within the desirable pH range is extremely small (MCLs are met) (Fig. 12.9). Precipitation of metal-sulfides is normally carried out using Na2S or NaHS. However, not all metals precipitate effectively by sulfide. For example, chromium (Cr3+) precipitates effectively as a hydroxide rather than sulfide. 

Calculate the number of micromoles of Pi and 7-min phosphate in the entire volume of filtered solution. If the inorganic phosphate (in the unhydrolyzed sample) in the filtrate is less than 15% of the phosphate found after 7-min hydrolysis, you may proceed with the rest of the experiment. (NOTE When students are working in pairs, some instructors prefer to have one student proceed directly with steps 12 through 14 while the other student conducts the assays of steps 5 through 9. This assumes that the magnesium ammonium phosphate precipitation effectively removes most of the inorganic phosphate from your preparation, as occurs in most (but not all) cases. Consult your instructor.)... 

Precipitation effects inorganic retarders and setting accelerators... 

For very dilute nucleic acid solutions, precipitation with polyethylene glycol (PEG) is preferred. PEG 6000 is added to a concentration of 10% (w/v), and the solution is allowed to stand on ice for 2 h. The precipitate is removed by centrifugation and washed with 70% (v/v) ethanol. PEG can be used for fractional precipitation, since high molecular weight DNA is precipitated at lower PEG concentrations than low molecular weight DNA. It should be emphasised that oligonucleotides of chain length less than 20 cannot be precipitated effectively with either alcohol or PEG. 

In Norway comprehensive investigations of acid precipitation effects have taken place (Overrein, Seip and Tollan, 1980). Fish death caused by such influences in some districts in southern Norway has been proved. The soil material in this region is often shallow, coarse grained and derived from bedrock rich in silisium. The buffer capacity is therefore low and the acid effect of the precipitation will quickly be noticed. On the other hand, there has so far not been proved any decrease in the growth of the forest. In this connection we must remember that the acid precipitation also contributes with the nutrient element nitrogen. 

Overrein L., Seip H.M. and Tollan A., Acid precipitation - effects on forest and fish. Final report. 175 pp. Oslo-As (1980). 

Lowering the pH also leads to a decreased solubility of thrombosthenin. Grette (1962) obtained precipitation of porcine thrombosthenin at pH 6.5. The addition of small amounts of Mg++ ions seems to enhance the precipitating effect. Care must be taken, however, because even at pH 6 signs of progressive denaturation become discernible. It seems preferable for preparative purposes to work at a neutral pH. 

Cronan C. S. and Schofield C. L. (1979) Aluminum leaching response to acidic precipitation effects on high-elevation watersheds in the Northeast US. Science 204, 304-306. 

Schofeld, C.L. (1976) Acid precipitation effects on fish. Ambio, 5, 228-230. 

Benjamin and Leckie (1981) found a nearly complete lack of competition of Cd, Cu, Zn, and Pb for sorption sites of a noncrystalline Fe precipitate. The lack of competition of these cations may be related to low surface coverage and/or precipitation effects and only partially to the presence of different binding sites having high selectivity for specific trace element ions (Kretzschmar and Voegelin, 2001). 

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