tailieunhanh - PURIFICATION OF ORGANIC CHEMICALS

This module is the eighth in a series of Extension materials designed to provide Extension agents, Certified Crop Advisers (CCAs), consultants, and producers with pertinent information on nutrient management issues. To make the learning ‘active,’ and to provide credits to Certified Crop Advisers, a quiz accompanies this module. In addition, realizing that there are many other good information sources, including previously developed Extension materials, books, web sites, and professionals in the field, we have provided a list of additional resources and contacts for those wanting more in-depth information about soil pH and organic matter. This module covers the following Rocky. | CHAPTER 3 PURIFICATION OF ORGANIC CHEMICALS The general principles techniques and methods of purification in Chapters 1 and 2 are applicable in this chapter. Most organic liquids and a number of solids can readily be purified by fractional distillation usually at atmospheric pressure. Sometimes particularly with high boiling or sensitive liquids or when in doubt about stability distillation or fractionation under reduced pressure should be carried out. To save space the present chapter omits many substances for which the published purification methods involve simple distillation. Where boiling points are given purification by distillation is another means of removing impurities. Literature references are omitted for methods which require simple recrystallisation from solution if the correct solvent can be guessed readily and where no further information is given . spectra. Substances are listed alphabetically usually with some criteria of purity giving brief details of how they can be purified. Also noted are the molecular weights to the first decimal place melting points and or boiling points together with the respective densities and refractive indexes for liquids and optical rotations when the compounds are chiral. When the temperatures and or the wavelengths are not given for the last three named properties then they should be assumed to be 20 C and the average of the wavelengths of the sodium D lines repectively and densities are relative to water at 4 . The present chapter includes commercially available organic chemicals. Most of the organo- phosphorus boron silicon alkali metal compounds and metal ion salts are in Chapter 4. Naturally occurring commercially available organic compounds of use in biochemistry molecular biology and biology are included in Chapter 5. Abbreviations of words and some journal names are listed in Chapter 1 pages 1 and 2. As a good general rule all low boiling 100 organic liquids should be treated as highly flammable and the .