Polymers

Notes

ELECTROLYSIS

PRECIPITATION

EXTRACTION

Liquid-liquid phase separations are possible when a metal forms a compound soluble in two immiscible liquids. The distribution of the compound between the two liquids can be considered to be a solubility contest. Practical considerations dictate that one of the liquids must be water. Among the liquids other contestants are: carbon tetrachloride, chloroform, carbon disulfide, ethers, paraffin hydrocarbons, and aromatic hydrocarbons. Alcohols cannot be added to this list.

Most inorganic compounds just are not interested in the organic solvents which are immiscible with water. Sometimes, however, a complexing agent can be found which will coach an inorganic substance into an organic solution. Cupric, lead, zinc, silver, mercuric, and cadmium salts, for example, will dissolve, in either chloroform or carbon tetrachloride if it contains some dithizone.

The most generally useful technique for accomplishing a phase separation is the solid-liquid separation, obtained in a precipitation.

To have wide applicability a precipitant should form compounds with many metal ions, and these compounds should have a wide range of solubility. To obtain proper conditions, the concentration of the precipitant should be controlled easily.

What sort of precipitant is most desirable depends upon many variables: how many samples must be determined, what constituents are present, what reagents are at hand, what time is available, and what accuracy is desired, etc.

Another type of solid-liquid phase separation is furnished by electrolytic techniques. Two electrodes are placed in the solution of interest, and a current is passed through the solution at a voltage sufficient to reduce some but not all of the metals present. If the current and concentrations are adjusted properly, the metals which are reduced will plate out on the electrode in a pure metallic deposit which can be dried and weighed directly.

the solution of interest –розчин, що досліджується will plate out -відкладається

to reduce some but not all –для часткового видалення

The human body, all animal and plant tissues, and most building substances in organic nature, such as proteins, wood, consist of polymeric or macromolecular materials. Many minerals, such as silica and feldspar are inorganic polymers, and numerous products of ancient and modern industry such as porcelain, glass, textiles, paper, rubber and plastics are either entirely or substantially polymeric. All these substances possess one essential common feature; they consist of very large molecules.

A polymer is a substance consisting of molecules which are multiples of low-molecular-weight units. The low-molecular-weight unit is the monomer.

Isomeric polymers are polymers which have essentially the same percentage composition, but differ with regard to the arrangement of the individual atoms or atom groups in the molecules.

A homopolymer consists of macromolecules which are formed either by a single type of unit or by two (or more) chemically different types in regular sequence.

Copolymers are macromolecules containing two or more chemically different monomeric units in a more or less irregular sequence.

Дата добавления: 2015-01-03