Dielectrics ammonium sulfate

Organic solvents also decrease protein solubility, but they are not as widely used as ammonium sulfate. They are thought to function as precipitating agents in two ways (1) by dehydrating proteins, much as ammonium sulfate does, and (2) by decreasing the dielectric constant of the solution. The organic solvents used (which, of course, must be miscible with water) include methanol, ethanol, and acetone. 

Proteins are commonly least soluble at their isoelectric points. Hence, a combination of high salt concentration and pH control is used to achieve salting out. Protein mixtures can be separated by a stepwise increase in the ionic strength. Care must be taken with some proteins because ammonium sulfate can denature the protein. Alcoholic solvents are sometimes used in place of salts. They reduce the dielectric constant and subsequently reduce solubility by lowering protein-solvent interactions. 

Sometimes, the exchange does not work well under reflux conditions. A few alternatives are the use of phase transfer catalysts (ammonium or phosphonium salts), crown ethers, or exchange in melts or under solid-state conditions (Apparu and Madelmont, 1998). Melts are either the substrate itself at its melting point (where it has to be stable, and must have a high dielectric constant to solubilize Na I), a melt of acetamide or formamide, or ammonium sulfate below its melting point (reaction at 120—160°C). This technique is mostly used with aromatic compounds (Seevers and Counsell, 1982). 

A typical electroless plating solution is composed of a cation provider such as nickel sulfate, a reducing agent such as ammonium hypophosphite, and additional additives tiiat help prevent the bath from decomposition, i.e., plating spontaneously. When an activated substrate is immersed in the plating bath at a temperature of 80 C and a pH around 6, nickel cation in the bath are reduced by hypophosphorous acid, and the nucleation of nickel deposition starts at the activated locations. Because nickel readily plates to itself (self-catalysis), the deposition continues and eventually fills the via locations in the dielectric with nickel metal. The reduction reaction can be expressed by the following equations ... 

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