FRIEDRICH EMICH, FRITZ PREGL, FRITZ FEIGL Three Austrians as Pioneers in Microanalytical Research GERALD KAINZ University of Vienna, Vienna, Austria (Translated b y Ralph E. Oesper, University of Cincinnati)
A
PERUSAL of the current literature of analytical chemistry reveals that most of the researches deal with the detection and determination of small or extremely small amounts of materials; in other words, t,he methods involved are those know11 as micro- or ultramicro procedures. The analysis of slight quailtities of materials is by no means a fad or a stunt. Many substances, particularly natural products or t,he active materials of animal or plant cells, are preparatively accessible only in minute amounts or, as in nuclear research, are actually harmful in larger amounts. Their study becomes an impossibility wit,hout trustworthy analytical methods. Futhermore, tiny quantities of substances t,hat are present as admixtures or contaminants in elemcnts or compounds frequently are decisive factors in biology and t,echnology. The reliable detection or quantitative det,ermination of such "traces" is often of enormous importance to the testing of materials of all kinds and frequent,ly is a problem in the biological sciences. As late as the beginning of this century there were hardly any methods available for the detection or determination of tiny amounts of subetances. Such procedures mere still to he created. This paper deals with t,he three Aust,rian chemists who broke the t,rails in this region and thus pointed the way for later studies They were: Friedrich Emich, the founder of inorgauic quantitative microanalysis (Graz), Fritz Pregl, the founder of organic quantitative micronnalysis (Graz), and Fritz Feigl, the founder of inorganic and organic spot test analysis (Vienna, now Rio de Janeiro). Their names are indissolubly associat,ed vit,h t,he development and progress of microanalysi~.
FRIEDRICH EMICH (1860-1940)
Friedrich Emich IT-asborn a t Graz on September 5, 1860, aud studied chemistry a t the Technische Hochschule there from 1878 t,o 1884. He became Privatdozent in 1888, Associate Professor in 1889, and served as Ordinarius a t this universit,y from 1894 to 1930, in geueral and experimental chemistry. Around the middle of the 1890's, Emich turned his at,tention to the analysis of minimal amounts of materials. At the start he used various precipitat,ion reactions under the microscope, as had heen done hefore him by Th. Behrens. However, Emich soon
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was able to frrr microun:~lysis from the microscope and to adapt the met,hods of general chemistry t,o these tiny dimensions. Thus, for example, with the aid of the so-called thread reactions he mas able to detect ae little as 3.10-'O g. of NaOH or 5.10-'0 g. HCI, in that he observed the color reaction of a silk thread soaked in litmus. A thread impregnated with sulfide made it possible t o detect heavy metals in amounts down to 10-g g. He also detected g. of nitrogen and the sulfur in 2 mm. of a hair taken from the head. However, t,he center of his researches lay in t,he field of quantitative inorganic microanalysis. He was the founder of t,his branch. The initial step in microgravimetry was to find a suitable balance. Emich refined the then known torsion balances of Xernst and Angstrom to the point that the Nernst balance would indicate as little as 0.1 pz. under a load of 500 mg. and the Angst,rom bn1:mce as lit,tle as 0.015 pa. under a load of 2 mg. Of course, the restricted weighing range permitted the use of only tiny crucibles and filtering devices. Hence Emich later employed the beam halance of Kuhlmann, with a range of 0.01 mg.-20.0 p. which was subsequently improved hy F. Pregl to an accuracy of + 0.001 mg. But Emich's researches on the tortion halances \%.ere not made less important, his studies constitut,e the hasis of the ultra microbalances of tod3y. Moreover, a whole series of other microanalytical devices are due to Emich; in part,icular, the filter stick and the filtering beaker. Wit,h their aid it is possihle JOURNAL OF CHEMICAL EDUCATION
to isolate even the tiniest amounts of precipitate without loss and bring them on the balance. Because of these fundamental devices, quantitative inorganic microanalysis experienced a remarkable growth. Accurate separation methods and schemes of analysis were developed for minerals and alloys, a methodology whose elaboration was due in large part to A. Benedetti-Pichler (Graz, now New York) and especially F. Hecht (Vienna), who by the introduction of organic precipitants raised the accuracy of the micro methods still more. Emich's accomplishments as founder of quantitative inorganic microanalysis were formally recognized by conferring on him the Lieben Prize (Academy of Sciences in Vienna), the Liehig Memorial Medal (Verein Deutscher Chemiker) and by election to the Academies of Science a t Vienna and Halle. Emich received honorary degrees from the Technische Hochschule a t Aachen, the University of Graz, and his alma mater the Technische Hochschule at Graz.
of the hydrogen, carbon, and nitrogen in acetanilide along with its molecular weight. In this same year Pregl was called to head the medicinal-chemical department Graz. Here, assisted by long-time associate and subsequent successor,
Fritz Pregl (1869-1930)
FRITZ PREGL (1869-1930)
Fritz Pregl was born on September 3, 1869, at Laibach, which was then in Austrian territory. He studied medicine a t the University of Graz, received the doctorate in 1893, and became Privatdozent for physiological chemistry in 1899. In 1910 he was called to Iui~sbruckas Ordinarius (head) for medical chemistry, where initially he worked chiefly with biochemical problems. The degradation of bile acids yielded one product in such small amount that he could not hope to analyze it by the decigram method then ordinarily employed. He decided to develop methods which would permit the successful accomplishment of ultimate analyses with milligram amounts, i.e., with '/loath of the usual sample weight. Possibly he was led to hope for success in this venture because of what Emich had already accomplished in the inorganic field. One of the most important prerequisites for solving the problem was a balance which would respond to as little as 0.001 mg. There was of course available the Nernst balance as improved by Emich, but with respect to the determination of hydrogen and carbon there was the impediment that the changes in weight of the absorption apparatus are in the milligram range whereas the vessels themselves may weigh up to 10 g. The weighing range of the Xernst balance was far from adequate to meet this condition. In association Rith the balance-maker W. Kuhlmann (Hamburg), Pregl improved the latter'? "assay balance for rare metals" so that at a maximum load of 20 g. it was still possible to make weighings with an accuracy of 0.001 mg. Additional difficulties arose during the development of the milligram-procedures because many errors of macroanalysis with a 0.1 g. sample are still within the tolerance limit and accordingly are hardly noted, whereas with samples only '/lonth as large, they occasion large differences. Pregl was able to track down numerous sources of error and to eliminate them. On February 27, 1911, he gave an account of his new methods to the German Chemical Society in Berlin. In 1913, he demonstrated before the Naturforschertagung (scientific congress) in Vienna the determination VOLUME 35, NO. 12, DECEMBER, 1958
Haus Lieb,' he devoted himself almost entirely to the development and extension of organic micro met,hods. His "Die quantitative organische Milroanalyse" appeared in 1917, and acquired world fame. Since 1935, it has been carried forward by his pupil H. Roth and has been issued in numerous editions and translations. As might be expected, Pregl's outstanding accomplishments soon earned for him the recognition and suitable appreciation they deserved. They were hailed as the greatest advance in the field of organic ultimate analysis since Liebig's time. Among the honors which came to him were the Lieheu Prize, membership in the Vienna Academy of Sciences, an honorary doctorate from the University of Got,tingen, and in 1923, the Nobel Prize. Despite enticing edls to the University of Berlin and the University of Vienna, Pregl remained true to his a h a mater and to Graz which had become a second home to him. FRITZ FEIGL
Born in Vienna on May 15, 1891, Fritz Feigl studied chemistry at the Technische Hochschule (Technical Universit,~)and there received his doctorate of techuical sciences. From 1919 to 1938, he was associated with the 11. Chemisches Institut of the University of Vienna, where he became Docent for analytical chemistry in 1927. He was appointed to a professorship in 1935. Because of the political atmosphere, Feigl was forced to leave his homeland in 1938. After a short period a t Ghent (Belgium) he was once more compelled to flee. I n 1941, he accepted a call to the Ministerio da Agricultura in Rio de Janeiro, where as director of a large laboratory he carries on his researches indefatigably. Despite the injustices to which he and his family were subjected in 1938, Feigl has only kind feelings toward his again liberated country. Eveu in his doctorate work Feigl dealt with t,he qualitative detection of tiny amounts of various substances and worked out a scheme for the elements of the ammonium sulfide and hydrogen sulfide groups. He coilductad the reactions on filter paper and, with the aid of color reactions. was able to detect amounts
as low as to g. These studies were then extended to all cations and anions. Of course it was impossible t o carry out on paper reactions which required heating or which had to be conducted in strong acid or base. I n such cases Feigl conducted the reaction in micro drops on a spot plate, a watch glass, or in a micro crucible. He classified all tests in accord with their fundamental characteristic (for example, drop reaction, color reaction, crystal precipitation) and in each case. determined the smallest amount that could still just be detected as well as the lowest still detectable concentration, from which the limits of the test could be calculated directly. At that time the expression "sensitivity of a test" was used in a very confused fashion, and accordingly Feigl defined this concept exactly and suggested the terms "identification limit" and "dilution limit." As early as 1923, Feigl recognized that the translation of classical detection procedures to the milligram or microgram range could not he the exclusive ohjective of qualitative analysis employing slight amounts of the test substance. Characteristic of his prescience is a passage from a paper published in 1923: The clumsy scheme of qualitative analysis with its many sources of error must be retained in microanalysis solely beeau~e a t present we have available entirely too few specific and special reactions. Nevertheless, even now we see a. possibility of radically simplifying the future qualitative and quantitativeanalysis. I t resides in the planned search for and systematic use of complexehemied, specific special reactions with the aid of organic reagents.
These words characterize his subsequent researches, whose objective from then on was to avoid as much as possible the precipitations and filtrations so inherent in the usual macroanalytical procedures, and to replace them with specific reactious so that the ion in question could he detected directly in the sample or its solution. With this in view, Feigl tried out a large numher and variety of organic compounds with respect to their suitability in analysis, and he introduced many new organic reagents. But only a relatively few of the organic reagents introduced are specific for certain ions; the majority show a selective action a t most, i.e., only several ions respond poeitively. To make such tests specific, Feigl used two methods primarily: determination of the optimum pH regian, and masking of the interfering ions by means of organic and inorganic reagents. This procedure is now called "conditioning of tests" and is widely used. In his search for specific reagents Feigl introduced, for the first time, the use also of catalytic and induced reactions in qualitative analysis. These respond to extremely small amounts and, for the most part, are specific for certain substances, as for instance the iodine-azide reaction for inorganic and organic sulfide compounds. Fiegl has now succeeded in reducing the preliminary division into groups of ions to a minimum, and primarily because of his studies many elements of the periodic system can now be detected directly in the sample. This not only represents a tremendous saving of time hut also accomplishes a significant reduction of the quantity of sample needed for the analysis. The Feigl methods, which are also known as spot test analysis, require only to g., and hence are qualitative ultramicro methods.
Feigl has also devoted much of his research t o the spot test analysis of organic materials. In the last five years he has opened new and original paths. He has discovered and developed specific tests for many functional groups and has made available numerous sensitive tests for particular organic compounds. One of the most important areas of the application of spot test analysis is now found in paper chromatography; the detection and identification of the compounds that have been separated chromatographically are frequently accomplished by Feigl tests. It can be justifiably stated that spot test analysis has contributed fundamentally to the rapid rise of chromatography. The number of his publications is now near 300. Their distinguishing characteristic is that they not only describe the analytical details of the test but also attempt to give the scientific background of the reaction. Special note should be taken of hia book "Chemistry of Specific, Selective and Sensitive Reactions" (1949) which contains a wealth of information and suggestions drawn from his extraordinarily wide experience and knowledge. His great acquaintance with the field of qualitative micro- or ultramicroanalysis is exhibited in his books: "Qualitative Analyse mit Hilfe von Tupfelreaktionen" (3 editions); "Qualitative Analysis by Spot Tests" (5 editions); "Laboratory Manual for Spot Tests." T h e ~ estaudard tex,s serve analysts throughout the world. Feigl's accomplishments as founder of inorganic and organic spot test analysis have thus far been honored by the receipt of the Haitinger Prize (1929) and by the first award of the Pregl Prize (1931) and by election to the Academy of Sciences in Vienna. He was also the first recipient of the Emich Medal conferred (1951) by the Oesterreichische Gesellschaft fur Mikrochemie. He received the Weizmann Prize in 1952, and the Exner Medal (1957) of the Niederoesterreichische Gewerbeverein. An honorary doctorate came to him in 1948 from the Technische Universitat of Vienna. His adopted country, Brazil, has bestowed many honors on him. He is an honorary citizen of Rio de Janeiro, and the universities a t Sao Paulo and Rio de Janeiro have awarded him honorary doctorates. He was elected t o the Brazilian Academy of Sciences, JOURNAL OF CHEMICAL EDUCATION
which chose him as Einstein medalist in 1957. A laboratory at the University of Recife in the state of ~ernambuco,Brazil, bears h& name. Feigl is an honorary member of the Verein Oesterreichischer Chemiker and the Oesterreichische Gesellschaft fiir Mikrochemie. which each vear confers a Feigl Prize for outstanding work by young Austrian microchemiets. He is likewise an honorary member of
VOLUME 35. NO. 12, DECEMBER, 1958
the British Society for Analytical Chemistry, and of the Japanese Society of Analytical Chemistrv. ACKNOWLEDGMENT
The author is indebted to Professor of M. K. Zacherl (Vienna) for valued assistance and advice in the composing df this paper.
