Plant and animal substances

SOURCES, NATURE AND COMPOSITION OF PLANT AND ANIMAL SUBSTANCES Only two types of organisms, found on the earth, are able to synthesize organic matter... 

In the early stages of decomposition of plant and animal substances many simple substances are formed that can readily react as chelating materials. Many, or most, of the reaction products would be water soluble but probably rather transitory since they would be subject to further biological attack. 

Concentrations of WA and their derivatives should be firstly measured in air, soil, surface, ground and discharge waters, bottom sediments, plant and animal substances as well as in industrial wastes. In some cases, WA and TP concentration measurements may be necessary in other objects potentially hazardous for the environment. 

Eighteenth-century chemists cautionary remarks about the inadequacy of their analytical means in plant and animal chemistry can hardly be overlooked. Ibey are repeated over and over again in practically all of the eighteenth-century publications dealing with the analysis of plant and animal substances. See also ch ters 12 and 13. 

Furthermore, the different contexts in which the chemistry of pure substances was embedded in the early modern period show that it maintained quite distinct enterprises of theory and practice. Being part of both metallurgy and pharmacy, our term chemistry of pure substances denotes a common ground for a variety of different chemical practices rather than one distinctive field of chemistry with clearly established contours. As to academic chemistry, the study of metallurgical substances existed only as a facet of the much wider field of mineral chemistry, and the pharmaceutical study of pure chemical substances was linked closely with that of plant and animal substances. In areas which look like a distinct domain of chemistry, as in the case of the investigation of neutral salts at the Parisian Academy, certain shifts in focus are responsible for this effect rather than the incipient formation of a well-defined discipline. Not surprisingly under such circumstances, there was not even a name used to denominate this occupation with pure chemical substances as a distinct chemical practice. 

F. L. Flolmes presented all later eighteenth-century plant analysis as the analysis of proximate principles of plants by means of solvents. Therefore we wish to emphasize that almost all eighteenth-century chemists we have studied actually also further analyzed the substances extracted fixrm plants by dry distillation. In so doing, many of them even tried to study the different proportions of the distillation products. Lavoisier s elemental analysis of plant and animal compounds continued to some extent an old tradition that was never given up when chemists became more interested in the proximate principles of plants. But Lavoisier also changed both the technique and the conceptual resources for analysis of the elemental composition of plant and animal substances. See also our explanations in chapter 14. 

What had happened in the period between 1782 and 1792 that spurred Fourcroy to select from the former class of proximate principles of plants only those that were composed of carbon, hydrogen, and oxygen, and in some cases also of nitrogen In 1789, A.-L. Lavoisier had proposed a new analytical definition of plant and animal substances that was to become a compelling proposition almost immediately after its... 

Ibid. p. 55. It should be noted that this phrasing highlights that Lavoisier s and Fourcroy s theory of the composition of plant and animal substances did not imply the stoichiometric law of a definite, invariant composition. We will discuss this problem in detail in chapter 14. 

Lavoisier s analytical program for classifying plant and animal substances... 

In accordance with this approach, Berzelius was never willing to recognize substances produced in the chemical laboratory by the chemical metamorphosis of extracted plant and animal substances as organic. He never grouped these artificial organic substances together with the extracted natural ones. 

The carbon compounds individuated and identified in carbon chemistry—the remaining stoichiometric plant and animal substances and the pure carbon compounds isolated from coal tar, as well as the artificial carbon compounds created in the laboratory—were nested in extended networks of experiments and work on paper. In the late 1840s, when the culture of carbon chemistry was firmly established, the individuation and identification of carbon compounds required quantitative elemental analysis, control of stoichiometric purity by studies of the chemical properties and reactions of a substance, experimental examination of their proximate components or constitution (later structure ), and work on paper with chemical formulae to demarcate the substances and to model their constitution and chemical reactions. Analysis of composition (qualitative and quantitative), control of purity, studies of reactions, and modeling on paper allowed chemists to draw ever more sophisticated... 

As we showed in part III, the new concept of organic substances was even unintentionally reinforced by Lavoisier s theory of the elemental composition of plant and animal substances. 

By contrast, plant and animal materials did not display these features. Reversible decompositions and recompositions and replacement reactions were not found in chemical operations performed with chemically extracted plant and animal substances. For the entire eighteenth century the resynthesis of plant and animal substances from their analytical products seemed to be out of the question. Similarly impenetrable to chemists was the question of whether and how chemical affinities governed the chemical changes of plant and animal substances. With the exception of vegetable and animal acids and alkalis, patterns of elective reactivity were hard to observe in chemical transformations of plant and animal substances. Instead of two products, plant and animal substances often yielded cascades of reaction products that could not be systematized along lines developed in the area of substances which we have designated chemistry of pure substances. ... 

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