Further Reading

Chapman JR (1993) Practical Organic Mass Spectrometry. A Guide for Chemical and Biochemical Analysis, 2nd edn. Chichester: John Wiley. Johnstone AW and Rose ME (1996) Mass Spectrometry for Chemists and Biochemists. 2nd edn. Cambridge: Cambridge University Press. Krumbiegel P (1991) Stable Isotope Pharmaceuticals for Clinical Research and Diagnosis. (Drug Development and Evaluation), vol.18. Jena: Fischer. McLafferty FW and Turecek F (1993) Interpretation of Mass Spectra. 4th edn. Sausalito: University Science Books.

Carbon and hydrogen constitute 80-95% of the resin and asphaltene molecules, with oxygen always present. Sulfur, nitrogen and metals are also usually present. The content of resins in crude oil (2-40%) exceeds by far (from 3 to 40 times) the content of asphaltenes (trace to 6%; usually <1%). Carboids and carbenes, which resemble asphaltenes, differ from them by having a higher oxygen content. However, they are absent in crude oils and distillate cuts. In small quantities, they are found in residues from vacuum distillation, in cracked tars, and in native and petroleum asphalts.

Bitumens and the related heat-treated asphalt are a very complex mixture of compounds with a wide range of molecular weights, which are difficult to isolate into classes of pure compounds. Resins are semi-liquid (sometimes almost solid) dark brown to black substances which have a specific gravity around 1 and a molecular weight of 500-2000 (usually 600-1000). Asphaltenes, on the other hand, are dark, amorphous powders and have a specific gravity greater than 1 and molecular weights of 1000-10 000 (average 5000). Using various methods, the observed molecular weights suggest that asphaltenes form molecular aggregates or colloids, even in dilute

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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