Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

46 ORGANIC ELEMENTARY ANALYSIS
of preparative work are intended to further the educational object above
indicated, and should be taken seriously. The carrying out of these
reactions should be considered just as important as the purely preparative
work.
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.
General aids to the study here outlined should be sought during
the practical course in Hans Meyer's thorough work, Analyse
und Konstitutionsermittlung organischer Verbindungen. Formal
schemes of analysis, leading to the classification of organic substances,
have also been worked out, e.g. by H. Staudinger in his
Anleitung zur organischen qualitativen Analyse, 2 Aufl., Berlin, 1929.
ORGANIC ELEMENTARY ANALYSIS
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 nig. cannot
be used for weighing 20-30 mg. of substance. Accordingly a
modern analytical balance (pointer reading method), a Kuhlmann
1 F. Pregl and H. Roth, Die quantitative organ. Mikroanalyse (Springer, Berlin,
1935); cf. H. Berger, J. pr. Chem., 1932, 133, 1 ; K. Kuspert, Chem. Fabr., 1933,
6, 63; E. Sucharda and B. Bobrahski, Semimicro-Methods for the Elementary
Analysis of Organic Compounds (London, 1936, A. Gallenkamp).