Volume 1

Victor von Richter's organic chemistry, or, Chemistry of the carbon compounds / edited by R. Anschütz ; authorized translation by Edgar F. Smith.

  • Richter, Victor von, 1841-1891.
Date:
1912
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Victor von Richter's organic chemistry, or, Chemistry of the carbon compounds / edited by R. Anschütz ; authorized translation by Edgar F. Smith. Source: Wellcome Collection.

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    qualitatively and quantitatively, the elements of a carbon compound after it has been obtained in a pure state and characterized by definite properties, crystalline form, specific gravity, melting point, and boiling point. Simple practical methods for the direct determination of oxygen do not exist. Its quantity is usually calculated by difference, after the other constituents have been found. DETERMINATION OF CARBON AND HYDROGEN. The presence of carbon in a substance is shown by its charring when ignited away from air. Ordinarily its quantity, as also that of the hydrogen, is ascertained by combustion. The substance is mixed in a glass tube vvith copper oxide and heated. The cupric oxide gives up its oxygen, is reduced to metallic copper, while the carbon burns to carbon dioxide, and the hydrogen to water. In quantitative analysis, these products are collected in separate vessels, and the increase in the weight of the latter determined. Carbon and hydrogen are always simultaneously determined in one Operation. The detailsof the quan- titative analysis are fully described in the text-books of analytical chemistry.* It is only necessary here, therefore, to outline the meth- ods employed. Liebig deserves much credit for his elaboration of these methods (Pogg. A. (1831), 21, 1). As a usual thing, the combustion is effected by the aid of copper oxide or fused and granulated lead chromate in a tube of hard glass, fifty to sixty centimetres long (depending upon the greateror less volatility of the organic body). Substances, which bum with difficulty, should be mixed with finely divided cupric oxide, finely divided lead chromate, or with cupric oxide to which potassium bichromate has been added. The combustion tube is wawn into a point, and the contracted end given a bayonet- shape (Liebig), or it is open at both ends (Glaser, A. Suppl. 7, 213). Cloez has also suggested the use of an iron tube (Z. anal. Ch. 2, 413). The tube is placed in a suitable furnace, which formerly was heated by a charcoal fire, but at present gas is exclusively employed (A. W. Hofmann, A. go, 235 ; 107, 37; Erlenmeyer, Sr., A. 139, 70; Glaser, /. c.; Anschütz and Kekulö, A. 228, 301; B. 25,2723). When the tube has been Glied, the open end is attached to an apparatus designed to collect the water produced in the combustion. The substances used to retain the moisture are: 1. A U-tube filled with carefully purified calcium Chloride, which has been dried at 1800 C. 2. Pure, concentrated sulphuric acid contained in a spiral-shaped tube, or pumice fragments, dipped in the acid, and placed in a U-tube (Mathesius, Z. anal. Ch. 23, 345)- 3. Pellets of glacial phosphoric acid, contained in a U-tube. The vessel intended to receive the water is in air-tight connection with the apparatus designed to absorb the carbon dioxide. For the latter purpose a Liebig bulb was formerly employed, but later that of Geissler came into use, and verv recently Delisle (B. 24, 271) has recommended a similar absorption vessel. In commercial work U-tubes, filled with * Anleitung zur Analyse organischer Körper, J. Liebig. 2. Auf!. 1853. Quantitative chemische Analyse, R. Fresenius. 6. Aufl., Bd. 2, S. 1-110. Chemische Analyse organischer Stoffe, von Vortmann.