Salt Ions Shield Charged Objects

Chapter 23. Salt Ions Shield Charged Objects in Solution... [Pg.434]

In this chapter we explore how ions shield charged objects. First we define what we mean by added salt. When you buy a bottle of some charged molecule, such as DNA, it will be electroneutral, so it will already have a stoichiometric complement of counterions. So you may get Na+-DNA or Mg -DNA, for example. With no additional salt, such solutions remain electroneutral. This is called the no salt condition. We are interested in conditions when additional salt is... [Pg.433]

Salts Dissociate into Mobile Ions and Shield Charged Objects in Water... [Pg.433]

The Poisson-Boltzmann and Debye-Hiickel models are relatively successful predictors of the shielding of charged objects by dissociated salt ions. But these models are approximate, and they have limitations. The Debye-Hiickel model shows that when salts dissociate into ions, the ions are not distributed uniformly, but are clumpy. There is an enhanced concentration of negative ions around each mobile positive ion, and vice versa. The main nonideality of salt solutions is attributed to this dumpiness. [Pg.444]

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