FISHER AWARD ADDRESS
From Buret and Balance to Spectrometer and Titrimeter HOBART H. WILLARD Unhersity of Michigan, A n n Arbor, Mich.
P
ROBABLY the greatest reward of a teacher is not the re-
search accomplished but the stimulating contacts with the students who made possible this research and the lasting friendships which result. Although the student may gain much from the close association with his teacher, the latter owes the student a debt of gratitude for the years of conscientious lvork on his thesis problem which is usuall) one of much interest to the teacher. Whatever reputation a man may acquire is due largely to the work of these research students and I wish to express my deep appreciation to the many n ho, over the past 40 years, have contributed to the work which has culminated in my receiving the Fisher Award. The importance of a particular research, like the greatness of a man, can be appraised only after the passage of years. There is inertia in the adoption of a new process or a new reagent. There will be mentioned later a few of the reagents and processes developed at the University of Michigan which seem to have been particularly useful. In future years these may be superseded by better ones, and some which now seem less important may well become more so. hnalytical chemistry is advancing by leaps and bounds. There is a better knowledge of the principles underlying the various procedures. Old methods are being improved and new ones discovered. PAST RESEARCH IN ANALYTICAL CHEMISTRY
At the University of Michigan there has always been much interest in new reagents. One of the earliest m s in perchloric acid which a t that time was available only in the form of an impure 20y0 solution. It seemed that the unusual properties of this acid had not been recognized and the acid was not easily prepared by existing methods. The more the reactions of this acid were investigated, the more important its properties seemed to be. A publication from this laboratory in 1906 described the use of silver perchlorate as an electrolyte for the silver coulometer. Six gears later a method for the preparation of this acid from the ammonium salt was published and this process was used commercially for many years. The use of perchloric acid as a dehydrating agent for silica came later. About this time there came to the University of Michigan a graduate student whose doctoral thesis covered a study of many of the salts of’perchloric acid. S o t many men follow the line of work covered in their theses, but G. F. Smith became so interested in this subject that when he went to the University of Illinois as instructor he had recognized the need of making perchloric acid available. I n 1924 he converted his garage into a factory for the manufacture of this acid and continued to operate it until the neighbors objected to the fumes; then he moved it to Columbus, Ohio. Dr. Smith is an unusual type of analytical chemist because he not only devises new methods but also manufactures the unusual reagents which are often required. I t is aviomatic with him that a reagent which is not available will not be widely used, no matter how useful it may be. Another reagent which has many uses is periodic acid. Here, too, it was necessary to devise a method for its preparationthe electrolytic oxidation of iodine. iigain Dr. Smith used this process to make it commercially available. The use of periodate as a colorimetric method for manganese was published in 1917 and is m w widely used. In 1928 Malprade found it extremely useful in reactions with polyhydric alcohols. The advantages of ceric sulfate as a volumetric oxidizing agent
were recognized independently by S . H. Furman and the author. About this time Philena Young, a woman of unusual ability, came to the University of Michigan for graduate studies and began an investigation of this field which continued several years into postdoctoral nork. The work of Dr. Young resulted in the publication of 22 papers of which she was joint author over a period of about 6 years. Again Dr. Smith made the material available and helped to popularize its use, until now it is one of the most valuable titrimetric solutions. In 1933, shortly after the discovery of the relation between fluoride and dental caries, work was completed on a method for separating fluorine from numerous interfering substances by steam distillation as hydrofluosilicic acid, after which it was titrated with thorium nitrate. Coming a t a time when the interePt of the medical and dental professions had reached a new high, the value of this procedure was immediately recognized and it is now widely used. K o r k in this field has recently been continued. A line of research which has been pursued a t the University of llichigan for many years and which has proved very fruitful is precipitation from homogeneous solution. The first work on this method of adding one molecule of a reagent a t a time was started in 1937 and is still in progress. It has proved to be a very efficient method of effecting many difficult separations by reducing the errors due to adsorption and coprecipitation. In the search for new reagents and processes of practical interest theoretical research was not forgotten. In 1922 Florence Fenwick began publishing from the University of Michigan laboratory the results of research in the field of potentiometric titrations using polarized and bimetallic electrodes. The importance of her work has been demonstrated by the present extensive use of such systems. Dr. Fenwick’s researches continued in the laboratory of the U. S. Steel Corp. until her death a few years later. ERA OF BURET A11.D BALANCE
Qualitative analysis in 1900 under Professor Otis C . Johnson, coauthor of the well-known book by Prescott and Johnson, was a 10-hour course-laboratory and recitation 5 days a week. Such a course would be impossible now since even 5-hour courses are often difficult to fit into a modern curriculum. I t is amazing to think of the enormous increase in the subjects which have been crowded into the chemistry courses of today. Obviously many things v hich were important then are much less important now. But thorough training in analytical chemistry is still very important, probably more important that it was then. It is apparent that there was a great waste of time and effort in that 10-hour course. It included very little theory. Physical chemistry had not then found its place in a course in analytical rhemistry, although a small book by Ostwald entitled “Scientific Foundations of Analytical Chemistry” had appeared in 1894. The course in quantitative analvsis a t that time was a course in proceduresqand techniques-the era of the buret and balance. I t was a sort of cookbook course. Unfortunately there are still a few chemists who think of quantitative analysis in the same way today. There was no lack of reference and textbooks to which the chemist or the student could turn for directions on how to determine sulfate or calcium gravimetrically or to titrate an acid or an arsenite. The books might state iyhat substances would interfere but with meager information on the reasons for the inter1726
V O L U M E 2 3 , NO. 1 2 , D E C E M B E R 1 9 5 1 ference or on the errors involved. They t o u l d state what indicator to use in titrating an acid or a base but they failed to explain the reason why one indicator was suitable and another would give erroneous results. The term pH \\as not suggested until 1909 by S. P. L. Sorensen and there was no way of expressing the concentration of acid or base except in terms of normality. The conditions under which a given procedure should be carried out were, of necessity, somewhat loosely defined. I n spite of this lack of information the analytical chemists of those days made very accurate analyses. W. F. Hillebrarid and H. 8. JVashington a t the U. S. Geological Survey did ivonderful work on very complex materials, such as silicates in which many successive separations were required. A complete analysis was long and tedious just as a silicate analysis is today in spite of the improvements that have been made. Colorimetric methods were rare and the apparatus would seem rather crude to the analyst today. Organic reagents ahich are often quite specific were seldom available. The balances and burets were adequate, but the necessity for personal calibration of glassxare v a s much greater than it is now. Beakers and flasks were not very resistant to thermal shock or to the action of reagents. Chemicals were not so pure as they are today and often they had to be specially purified. C. A. F. Kahlbaum in Germany furnished the first accurately analyzed reagents. I n fact, the designation “Iiahlbaum, zur Analyse” signified the ultimate in purity. Eventually, analyzed reagents of high purity became available in this country. Fifty years ago there n a s comparatively little demand for very rapid methods of analysis because there was much less careful control of manufactured products and there was not the enormous production that developed later. Most of the so-called rare metals which are common today mere not in use then. The suggestion that metallic tantalum, titanium, and zirconium would be commercial products would have seemed fantastic. The methods of analysis seemed reasonably adequate and not many students mere interested in research in this field, but preferred organic or physical chemistry which seemed to promise more spectacular results. But a good foundation had been laid for development along a different line. The building blocks were there for those who knew of their existence and who had the imagination to conceive how they could be utilized. I n 1914 W. C. Blasdale published a textbook which for the first time endeavored to emphasize the theory of analytical processes. H. Bassett’s book, “The Theory of Quantitative Analysis,” was published in 1925 in England. H . .4. Fales in his textbook “Inorganic Quantitative Analysis,” published in 1925, laid much stress on teaching the principles of physical chemistry as well as procedures and techniques. In later books this trend was carried still further and today the theoretical aspects of analytical chemistry are emphasized as much or more than the procedures themselves. ERA O F INSTRUMENTATION
IVorld War I greatly accelerated the demand for many things and resulted in a great increase in industrial production. The greater number and variety of products and the more careful control required in their manufacture demanded rapid methods of analysis impossible by the classical methods. After the war there was a steady increase in production. Ken. elements were being utilized and older methods of analysis were found to be inadequate. This led to an increasing demand for men trained in research in analytical chemistry. To meet the demands of industry for better, faster, and more precise methods, it was necessary to utilize the fund of l a m , theories, and factual information and instruments gathered in the other fields of chemistrv, in physics, and in other branches of sL’ence. And then analytical chemistry began to emerge from the buret and balance stage. I t j, probably fortunate that this demand for new and faster
1727 methods came no sooner, because in order to utilize fully a discovery i t is often necessary to await some subsequent Lnowledge or invention. Thus, the principle of the glass electrode was published in 1909 but it w.as 20 years later before electronic devices for measuring potential through an extremely high resistance made its commercial development possible. During the succeeding years the analytical chemist turned to physics, physical chemistry, biochemistry, and nuclear chemistry where there u ere techniques, principles. and apparatus not previously utilized which seemed to be worth developing and applying to analytical problems. And so the analytical chemist moved into the nest era-the application of physical methods which might be called the spectrometer and titrimeter era, or, in more prosaic language, the instrumental era Titrimetry. The use of the hydrogen elpetrode in titrimetry was introduced by J. H. Hildebrand in 1912 as a method for the determination of magnesium in the presence of calcium but he also suggested the use of a platinum electrode for oxidation-reduction reactions. The technique of potentiometric titrations developed rapidly. The first commercial apparatus for this purpose was the Kelley apparatus which was available in 1916. Eric AIuller’s book on this subject appeared in 1921. Since that time the apparatus for measuring potential has been greatly improved and the final step n as the commercial production of automatic titrators which would not have been possible R ithout the intervening advance in application of electronics. The first p H meter using the glass electrode appeared in 1935. Conductometric titrations were discussed even before potentiometric, but because of certain disadvantages have never been widely used. Electrolytic Separation of Metals. The electrolytic deposition of metals has been used since very early days. I n this country they xere developed by Edgar F. Smith, whose first book was published in 1890, and then went through many editions. Electrolytic separation of metals was usually carried out a t constant current, and therefore, it &as not possible to effect a separation unless the electrode potentials of the metals were spaced a considerable distance apart. The measurement of potential was ascertained by a voltmeter across the terminals of the cell and the current density was specified in the procedure. The advantages of measuring and controlling the potential a t the cathode had long been recognized but because this required the operator’s undivided attention, this process was seldom used, It was not until electronic controls became available that a completely automatic device for this purpose was devised. The first commercial apparatus was described by Harvey Diehl in 1914 and since that time others have been devised. This added greatly to the value of electrolytic methods of analysis which were already an important part of analytical chemistry. It made possible the separation of metals with electrode potentials differing by only a few tenths of a volt. It has also proved useful in the differential reduction of certain organic groups. Polarography. The mercury cathode had been in use for many years with recent improvements making it still more valuable: however, the most important application of i t was discovered by J. Heyrovsk9 a t Charles University in Prague. At the suggestion of Professor Kucera he investigated the behavior of the dropping mercury electrode and his first paper was published in 1922. I n 1925, J. Heyrovsk9 and 11.Shikata described the first polarograph; the instrument was called a polarograph because it graphically recorded current voltage curves obtained with a polarized electrode. I t is improbable that Heyrovskg foresaw the enormous usefulness of this instrument. One of the original models was imported by the University of Michigan. It ran by clockwork and the current was recorded photographically. I t was ballyhooed in the newspapers because of the great build-up by the organization that brought Heyrovsk9 to this country for a lecture tour. Extravagant claims were made by nonscientific newsmen and the
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university received a large number of letters from persons who hoped that the instrument would analyze everything from beer to rocks. Heyrovskj. deplored this unfavorable publicity and he delivered an excellent series of lecture?. ;\bout 10 years ago a good coniniercial instrument became available. If this old instrument were placed beside the large modern recording polarograph that is now in common use it ~vouldafford a striking example of progress in the era of instrumentation. The polarograph has made possible the rapid determination of very small concentrations in a simple manner and it is indispensable in a modern laboratory. The polarograph has also made possible amperometric titrations that are useful in titrating small concentrations. The above determinations constitute only a few of its many uses, and it is equally necessary in a commercial routine laboratory and in a research laboratory. Spectroscopy. Although the spectroscope has been used for the qualitative detection of metals for a great many years, its use in quantitative analysis did not attain a sufficient degree of precision until Gerlach and Schweitzer in 1925 introduced the niethod of internal standards. Great improvements were made by men in the physics department of the Ihiversity of Michigan and commercial laboratories began to utilize this technique. Instead of using the arc or spark to escite the spectrum the oldest method used the flame. H. Lundegbrdh in 1929 was the first to use this for quantitative purposes but the first apparatus for accurately measuring the intensity of the spectral lines was described by European investigators in 1935. I n this country the first flame photometer was described by R. B. Barnes and coworkers in 1945 and shortly thereafter commercial instrument,s were available. These are much less expensive and are easier to operate than a spectrometer and are useful where the cost of the latter would not be justified and where liquids are being analyzed. At first it was necessary to photograph the spectral lines in order to compare their densities and this is still the rommon procedure, but in very recent years the photomultiplier tube used in the quantometer has made possible the quick simultaneous determination of a number of elements without the delay involved in the photographic process. RIore than any other instrument the spectrometer has made possible mass production analyses. The Aluminum Co. of America makes 5 to 6,000,000 analyses a year TTith a high degree of accuracy even for elements present in relatively high concentrat,ions. Colorimetry. Colorimetric methods are very old. In 1856 Sessler introduced his reagent for ammonia and the tubes used for comparing colors are still known by his name. Duboscq in 1S54 suggested the plunger type of colorimeter and many improvements and modifications of this instrument' have been made since that t'ime, the first in this country being by R. E. Klett, in 1917. Photoelectric colorimeters were described almost as soon as the barrier layer photocell was available. 0. Berg was granted a German patent in 1911 in which t'ransmitted light was measured by the photoelectric effect,. However, little appeared in the scientific literature until about 1926, and over the next 10 years several photocells were described. In 1930 B. Lange was granted a German patent for his photoelectric cell, although the photocell was probably available a few years preceding this and improved types were available soon thereafter. The first cells, because of their high fatigue effects, caused trouble in colorimeters hut this difficulty was solved in the mid-thirties and commercially built instruments became practical for chemists. The first Lange colorimeter a t the University of Michigan was obtained in 1934. The scientific journals in 1935 and 1936 described several colorimeters which are well known today. These colorimeters were designed essentially for biochemical work and had to be modified to make t,hem suitable for general use. Industry became keenly interested and the particular application which most excited their interest a t first was the colorimetric deter-
ANALYTICAL CHEMISTRY mination of niolybdehum in steel. -411escellent American instrument, became available in 1936 and since that time there have been many others. .4 distinct advance in colorimetry \vas the development of the spectrophotometer. A recording spectrophotometer covering the visual range became available in 1938 and in 1941 the Beckman instrument appeared. This covered both the visible and ultraviolet regions and greatly accelerated research in colorimetric methods. Other manufacturers have introduced spectrophotometers including recording instruments and prospective purchasers now have a choice of excellent pieces of equipment. Between 1940 and 1950 more than 700 papers which involved CHEMISTRY. colorimetric methods were published in AXALYTICAL The complete analysis of portland cement by such methods is recommended by a group of Swedish analytical chemists as a great time saver. Spectroscopy. Although considerable work on infrared spectroscopy was done by Coblena and others before 1905, its application to analytical problems had to await the development of better instruments, provided with sensitive detectors and suitable recorders. Some work was done during 1932 to 1939, but the first comprehensive paper describing the application of infrared spectroscopy to the problems of an industrial research laboratory was published in 1941. The synthetic rubber and aviation gasoline needs of World War I1 furnished the stimulus for a very rapid and remarkable development of infrared equipment suitable for use as a routine analytical control and this has made possible the analysis of complex organic mixtures in a few minutes or hours, which even if a t all possible by any other means would have required da)-s. The first mass spectrometer dates back to t,he work of F. \i., Aston in 1919, but the instrument which served as a model for more recent ones was constructed in 1932. It is only in recent years, however, that' the mass spectrometer has become an analytical instrument. It serves to analyze gaseous samples containing a larger number of components than can be determined by infrared or ultraviolet spectrometers. The petroleum industry has found it extremely useful. X-Ray Dzraction. One of the disadvantages of chemical methods of analysis is the destruction of the sample and the consequent difficulty of determining the original condition of the individual components of a material. X-ray diffraction methods have given us a means of determining the form in which a crystalline material exists without destroying it. The Bragg law set forth in 1913 is basic in all x-ray analysis, but it remained for A. W. Hull in 1916 to develop the use of crystalline powders as a practical method for "finger printing" chemical compounds. There is now a card index containing x-ray diffraction data on more than 10,000 individual compounds. Subsequent developments have led to refinements in apparatus and quantitative interpretation. X-ray spectrum analysis corresponding to optical spectroscopy was developed by Bragg and hloseley in 1913-14. At that time it was necessary to paste the unknown sample on the target of an x-ray tube, but within the past 10 years this technique has been greatly improved with the advent of x-ray tubes producing beams of great intensity which excite secondary characteristic fluorescent spectra in samples outside the tube and these fluorescent rays are then analyzed with the Geiger spect'rophotometer. Another recent development dating from 1946 has been the use of x-ray absorption as a method of analysis and in 1950 an entire symposium was devoted to absorption analysis. Radioactive Isotopes as Tracers. A very recent development of great value to the analytical chemist involves the use of radioactive isotopes as tracers. These isotopes, produced in the atomic pile, have been made available by the Oak Ridge Sational Laboratory since 1946. In detecting errors in analytical methods, in investigations of the mechanism of analytical processes, and in determining very minute amounts of various elements,
V O L U M E 23, NO. 1 2 , D E C E M B E R 1 9 5 1 this very new tool has been of inestimable value. Other applications of radioactivity such as activation analysis are now being itivestigated. Organic Reagents. Organic reagents have been used for niany years but the interest in them and the search for new ones J I M been greatly stimulated by the work of Feigl. A review of this subject was published by him in 1936. These compounds have greatly incrcased the number of spectrophotometric methods its well as serving to precipitat’e and separate various elements. The earliest reagent of the chelate type, nitroso-8-naphthol, was suggested in 1885 for the precipitation of cobalt and i.; still used t’or that purpose. I t was not until 190.5, however, that, the possible importance of using organic reagents in the analysis of inorganic substances was brought to the chemist’s attention in an obvious and emphat,ic manner. This was accomplished by the discovery of the nickel reagent, dimethplglyoxinie, by Tschugaeff and this reaction may be considered as ideal in a certain sense. It, hint,ed s t the great reservoir of organic compounds :tnd the possibility of an important simplification of difficult malytical separations through the use of specific organic reagents. hmong the enormous number of such reagents a few which have been more est,ensively used are mentioned here. The ammonium salt of nitrosophenylhydroxylamine under the name “cupferron” was introduced in 1909, benzoin oxime in 1925, &hydroxyquinoline and the phenylarsonic acids in 1026, orthcphenanthroline in 1933, and tetraphenl-larsonium chloride in 1939. Because the properties of an organic reagent can be modified by substitutions, much research has been and is being tlevoted to this field. A number of books have appeared on this subject. Exchange Resins and Chromatography. Recent,ly much work has been done on the use of exchangr resins and chromatography i i i analytical chemistry and it appears certain that these techniques are destined to be employed extensively in the future. I n the review of these two subjects in the .January 1951 issue of .\NALYTICAI. CmxIsTRY covering thr year 1 9 3 , there are 506 rrferences. Iri the hlarch 1951 issue alone there arc nine papers dealing with chromatography. Microanalysis. llention should be made of the tvchnique of microanalysis, introduced about 40 years ago and which has attained a position of much importance. T o make a general statement regarding the introduction of instruments, one may say that prior to 1935 few instruments in the modern sense were available to the analytical chemist. Because of the economic situation management or chemists did not seem interested except to mtisfy their scientific curiosity. In the years between 1935 and 1940 the demand for and the availability of analytical tools expanded amazingly. hIILESTONES IN THE PROGRESS O F ANALYTICAL CHEMISTRY
The progress and trend of analytical chemistry during the past Its growth and increasing importance are indicated by certain milestones. I n 1929 the appearance of 3 years have been traced.
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INDUSTRIAL A N D EXGIKEERIKG CHEMISTRY, AKALYTICAL EDITIOS, heralded the first serious attempt in this country to establish a separate journal devoted to analytical chemistry. In 1047 this was made an entirely separate publication under the name ~ ~ N A L Y T I C A CHmiIsTRY L and since that time instead of the exppcted decrease in subscriptions there has been a steady increase. I n 1930 a t the spring meeting of the AMERICAN CHEMICAL SOCIETY in Atlanta, Ga., a symposium was held on the general subject “Analytical Chemistry.” The attendance at thiR symposium was so great that it overtaxed the capacity of a fairly large room. There were papers on six topics including several electrical methods, microscopic methods, and applications of the photoelectric cell. S o t many years later entire symposia were held on these separate topics. The Division of Analytical and Micro Chemistry met for the first time in St. Louis i n the spring of 1941; in l!IM its name was changed to the Division of Analytiral Chemistry. At the present time it is the fourth largest division in the Society. This is a striking indication of the recent tremendous inrrtme in interest in analytical Chemistry. The course in instrumental methods a t the University of Michigan was begun in 1934 and has continued to increase in populasity and importance. The first textbook on instrumental methods of analysis appeartd in 1948. CONCLUSION
Although we are no\v in the spectrometer and titrator or instrumental era there is as much need as ever for research in new theoretical studic-s and in the search for new chemical reagent,s and new chemical twhniques. One must know what is to be measured and its significance before he can intelligently use the appropriate instrument. Moreover, instruments must alFays be calibrated and a strictly chemical analysis is often the basis for this calibration. The search must be continued for new reagents to use.in the colorimeters and titrators and for new separations and new reactions for the new elements that were formerly rare but are now becoming common. At the same time the instruments nerdcd to make the best possible use of these discoveries must be improved. The number of chemical reactions, the types of apparatus used, and the varied techniques utilized by the analytical chemist of today make one who is broadly trained in this field valuable in solving problems quite outside of analytical chemistry. JVith the increase in instrumentation a course in applied electronic^ seenis to be a desirable addition to the analyst’s training. I n this period of i n s t r y e n t a t i o n there is danger of negltyting some of the older and fundamental aapects of analytical chemistry. Let us utilize instruments wherever they can be helpful but let us not neglect the chemical side of the subject. In this way we can make certain that the Golden Age of analytical chemistry which we are entering will continue. RECEIVED LIay 4, 1951. Presented before the Division of Analytioal C h e ~ n istry at the 1 1 9 t h Jfeeting of the A M E R I C A N CHEMICAL 6 0 C I E T Y . BoPtCm, Mass.
