Preventive action precipitation

If an aqueous ammonia solution which is 0.1M is employed, the concentration of NH4 ion as ammonium chloride or other ammonium salt necessary to prevent the precipitation of magnesium hydroxide can be readily calculated as follows. Substituting in the mass action equation ... 

Poly[2-methoxy-5-(2 -ethyl-hexyloxy)-l,4-phenylene vinylene] (MEH-PPV) is an excellent conjugated polymer and broadly used in polymer photoelectron devices, but is difficult to electronspin directly. In the work by Zhao et al, core-shell structured nanofibers were fabricated by coaxial electrospinning MEH-PPV (shell) in chlorobenzene and PVP (core) in 1,2-dichloroethane [64]. MEH-PPV was soluble in the above two solvents, which prevented the precipitation of MEH-PPV and enhanced the adhering action between the two polymers in the coaxial electrospinning process. It should be noted that this is an unusual example of core-shell nanofibers where (a nonprocessable) PPV was spun as the shell and not in the core. These uniform core/shell PVP/MEH-PPV nanofibers with a highly fluorescent property can have potential applications in the fabrication of polymer nanophotoelectron devices. 

Practical laundry detergent formulations usually include builders for control of polyvalent metal ion activities so that the relevant salts of the anionic surfactant, which is usually present, are not precipitated out of solution. The presence of builders also has implications for the effectiveness of antifoam action because they may prevent the precipitation of calcium soaps. We can illustrate the relevant issues if we consider, for example, the concentration of calcium harduess uecessary to just initiate calcium soap precipitation in the case of a solution built by sodium tripolyphosphate at a pH >10.5. If we iguore the effect of solubilizatiou of soaps and calcium binding in anionic surfactant micelles, then, according to Irani and Callis [4],... 

Meta-Sn salts with alkalis precipitate meta-Sn02-aq less acidic than the ortho form not readily soluble in NaOH insoluble in NH3 and COs l soluble in not-too-concentrated KOH excess KOH precipitates potassium meta-stamiate(TV), soluble in water. Tartrate prevents the precipitation of Sn hydrous oxide by OH" and C03 similarly (ortho) SnCU gives no precipitate, but the action of meta-Sn" chlorides is unaffected—see 14.4.3 Reduced halogens below about some of these. 

Solution Stabilizers, The action of methanol in preventing polymer precipitation in formaldehyde solutions is probably due to the formation of hemiacetals which exist in a state of chemical equilibrium wuth the hydrated... 

Bronze disease necessitates immediate action to halt the process and remove the cause. For a long time, stabilization was sought by removal of the cuprous chloride by immersing the object in a solution of sodium sesquicarbonate. This process was, however, extremely time-consuming, frequentiy unsuccesshil, and often the cause of unpleasant discolorations of the patina. Objects affected by bronze disease are mostiy treated by immersion in, or surface appHcation of, 1 H-henzotriazole [95-14-7] C H N, a corrosion inhibitor for copper. A localized treatment is the excavation of cuprous chloride from the affected area until bare metal is obtained, followed by appHcation of moist, freshly precipitated silver oxide which serves to stabilize the chloride by formation of silver chloride. Subsequent storage in very dry conditions is generally recommended to prevent recurrence. 

Mode of Action. The fluoride ion inhibits enzymes, such as enolase, which require Mg as a prosthetic group, by precipitating a complex magnesium fluorophosphate thus it prevents phosphate transfer in oxidative metaboHsm. 

It precipitates surface proteins at ulcer base and act as a physical barrier, preventing acid, pepsin and bile from coming in contact with ulcer base. It also augments gastric mucosal PG synthesis thereby enhancing protective action. It has no acid neutralizing action. 

If a (3-adrenoceptor antagonist is administered prior to sufficient ol-radrenoceptor blockade, a hypertensive episode may be precipitated with cardiac failure and pulmonary oedema. Most intravenous anaesthetic agents have been used safely, but ketamine is contraindicated. Sodium nitroprusside can be used to achieve arteriolar dilation. Esmolol, a pi-selective antagonist with very short duration of action, is administered intravenously to prevent cardiac arrhythmias intra-operatively. After tumour removal, volume administration should be aggressive to maintain haemodynamic stability, and a noradrenaline infusion may be required. 

Naltrexone Nonselective competitive antagonist of opioid receptors Reduced risk of relapse in individuals with alcoholism Available as an oral or long-action parenteral formulation Toxicity Gastrointestinal effects and liver toxicity will precipitate a withdrawal reaction in individuals physically dependent on opioids and will prevent the analgesic effect of opioids... 

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