tailieunhanh - Humic Matter in Soil and the Environment: Principles and Controversies - Chapter 6

Đặc tính của chất Humic HÓA đặc tính Một phần của các đặc tính hóa học của vật chất humic đã được thảo luận trong chương trước đây về thành phần hóa học. Nó được cho là cần thiết để trang trải nó trong một chương riêng biệt, bởi vì nhiều vấn đề hoặc các chủ đề, làm cho nó quá lâu để chúng trong một chương. Ngoài ra với đặc điểm thảo luận trước đó, chất humic cũng thể hiện trọng lượng phân tử và tính năng rất đặc biệt quang phổ. Nhiều nhà khoa học đã cố gắng sử. | CHAPTERS CHARACTERIZATION OF HUMIC SUBSTANCES CHEMICAL CHARACTERIZATION Part of the chemical characterization of humic matter has been discussed in the preceding chapter on chemical composition. It was deemed necessary to cover it in a separate chapter because of the many issues or topics making it too long to include them in one chapter. In addition to the characteristics discussed earlier humic substances also exhibit molecular weights and very distinctive spectroscopic features. Many scientists have tried using ultraviolet-visible infrared and NMR spectroscopy in the identification of various humic substances with results that are surprisingly reproducible Orlov 1985 for materials considered by many to be fake or operational compounds. These remaining characteristics will be discussed more in detail below. MOLECULAR WEIGHTS The topic of molecular weights is closely related to the issue of Copyright n 2003 by Marcel Dekker Inc. All Rights Reserved. elemental composition and chemical formulas as discussed in Chapter 5. The possession of a formula composition implies the presence of a molecular weight which is a basic physical property of humic substances of profound importance for their chemical activity. As discussed earlier elemental composition chemical formulas and molecular weights are controversial issues in humic acid science. The use of molecular weights in characterization of humic substances also encounters many other problems because of their polydispersive nature. They possess therefore a wide spread in molecular weights causing many authors to consider humic substances to be very heterogeneous compounds Felbeck 1965 . With homogeneous macromolecules all particles have the same molecular weights. It is a well-known fact that molecular weights of humic substances can vary from as low as one thousand for fulvic acids to as much as several thousands for humic acids. Physically molecular weights can be expressed into 1 number average 2 weight .