Organic elementary analysis

In the course of the scientific work which succeeds the preparative course, and indeed whenever the chemist has to deal independently with a problem, questions requiring a knowledge of qualitative analysis continually arise. Because of the limited time available we have unfortunately hitherto not attained the ideal of following up the preparative work with a comprehensive course in the qualitative identification of organic substances, but nevertheless the closest attention should be given to this branch of study. 

The quantatitive determination of the elements in an organic substance is known as elementary analysis. In this process carbon and hydrogen are determined simultaneously, whilst a separate analysis must be carried out for the determination of each of the other elements. 

The meso-analytical methods here described are carried out with 20-30 mg. of material. They have been worked out on the basis of Pregl s micro-procedure by Dr. F. Holscher.1 For almost two years they have been in use in the Munich laboratories and have proved to be excellent they have displaced the macro-analytical methods completely here. 

The Balance.—For reasons which can easily be perceived an ordinary analytical balance, accurate to within only 0-1 mg. cannot be used for weighing 20-30 mg. of substance. Accordingly a modern analytical balance (pointer reading method), a Kuhlmann 

---

Malissa, H. Automation in Organic Elementary Analysis. Proceedings of the Analyt. Chem. Conference Budapest 1966. Vol. I, S. 21. 

V. Ya. Zakharans and T. A. Komarova, The History of Organic Elementary Analysis, Khimya, Vestn. MGU, 1990. 

Niederl, J. B. and Niederl, V. (1938). Micromethods of Quantitative Organic Elementary Analysis. Wiley, New York. 

Justus von Liebig (1803-1873) german analyst and organic chemist, most well-known by his works concerning organic elementary analysis. He was a student of Gay-Lussac. 

Several requirements must be met in developing a stmcture. Not only must elementary analysis and other physical measurements be consistent, but limitations of stmctural organic chemistry and stereochemistry must also be satisfied. Mathematical expressions have been developed to test the consistency of any given set of parameters used to describe the molecular stmcture of coal and analyses of this type have been reported (4,6,19,20,29,30). 

The standard procedure of organic chemistry at that time was to prepare (or isolate) pure substances, and characterize these substances by elementary analysis and molecular weight... 

When the metals were studied, the release of gases and vapors was observed. For example, Paracelsus reported that when iron was dissolved in sulfuric acid air comes out like a wind. The differentiation of these kinds of air took more than two centuries. Research on the analysis of gases was extremely productive in developing the basic methods to handle and study gases and even paved the way to design techniques for elementary analysis of the constituents of organisms. Thus the study of gases became the second epoch of analytical chemistry it is called the pneumatic age. ... 

Elementary analysis showed that an organic compound contained C, H, N, and O as its only elementary constituents. A 1.279-g sample was burned completely, as a result of which 1.60g of CO2 and 0.77 g of H2O were obtained. A separately weighed 1.625-g sample contained 0.216 g nitrogen. What is the empirical formula of the compound ... 

The product, which was readily soluble in organic solvents including acetone, tetrahydrofuran, and methylene chloride, was characterized by ES1-MS, H, and 13C NMR spectroscopy, diffusion NMR spectroscopy, SAXS measurements and elementary analysis. In the ESI-MS, multiply charged ions [51-n TFPB]n+ with n = 7—11 containing the intact coordination cage were observed exclusively... 

Still deactivation of the catalyst with time on stream (TOS) can be observed. This deactivation is mainly due to the adsorption of dodecene and heavy products on the catalyst which block its active sites for further reaction. Elementary analysis of the catalyst after the reaction has been carried out, and a significant increase of the carbon content was found. This confirms that the deactivation of the catalyst is due to strong adsorption of organic materials on the surface of the catalyst. 

All mentioned polymeric oxides, alkoxides, aroxides and carboxylates are intensely coloured and insoluble in organic solvents. The structures were estimated by elementary analysis, IR spectra and model reactions. The mechanism of the reactions with alcohols and phenols is described as nucleophilic substitution at the metal atom for alonium and gennonhun ions ... 

The conversion of TCB to metal free polymers needs some urea as initiator . The obtained polymers were divided into acetone soluble, DMF soluble, DMF insoluble and cone. H2SO4 insoluble fractions. The highest yield of products soluble in organic solvente (50% acetone or 75-80% DMF soluble) were obtain with 1,5-3 mole % urea at 573 K in 10 h. DMF insoluble fractions resulted at 573 K in 40 h with an urea concentration > 20 mole %. In every case elementary analysis is in good agreement with expected values. But the IR-spectra show some C=0 absorption (saponification) and broad background absorption (possible polynitrile 91) formation). An expected absorption typical for metal free Pc is present at 1000 cm. ... 

Identification and characterization of the structures of unknown substances are an important part of organic chemistry. It is often, of necessity, a micro process, e.g., in drug analyses. It is sometimes possible to establish the structure of a compound on the basis of spectra alone (ir, uv, and nmr), but these spectra must usually be supplemented with other information about the unknown physical state, elementary analysis, solubility, and confirmatory tests for functional groups. Conversion of the unknown to a solid derivative of known melting point will often provide final confirmation of structure. 

ISO 10694 (1995) Soil quality — Chemical methods — Determination of organic and total carbon after dry combustion (elementary analysis) (BS 7755-3.8 1995). 

---