The ROLE
of MICROCHEMISTRY in CHEMICAL .EDUCATION* PAUL E. SPOERRI The Polytechnic Institute of Brooklyn, Brooklyn, New York
Most textbooks on quulitative analysis stress physical- Analysis of the less common elements can be included in chemical views to the exclusion of men elementary instruc- the curriculum, as well as the detection of traces of impurition i n the use of organic reagents. In concentrating ties. The use o f a large number of standard organic reupon ionization and solubility product we risk killing agents can also be introduced. Microchemistry offers the curiosity of the student and giving him the impression many new possibilities. Whereas a full-sized laboratory that there is a ready-made explanation for everything. i s impossible in the home, a micro-laboratory costs little Time can be saved by employing microchemical methods. and i s practically without danger.
EDUCATION? and ICROCHEMISTRY, the chemical technic of rized in the J O U ~ N A L OF CHEMICAL handling very small quantities of substances, hence need only to he mentioned. However, the fact is only about thirty years old. Originally has been overlooked that a simplified application of the devised in order to investigate chemical processes oc- methods of microchemistry permits any student to curring in living cells, these methods have in recent have his own laboratory a t home. Whereas a fullyears been simplified and generalized and in a number sized laboratory is an absurdity in most households, of instances applied in college courses. Professor satisfactory experience proves that most operations of Engelder has been most successful in introducing, in inorganic, organic, or analytical chemistry can be this country, a course in qualitative analysis, which uses carried out quite successfully with microchemical micro methods without the use of the microscope. His methods on any kitchen table. Smce the experiments highly interesting results have already been summa- are naturally performed with small amounts of sub-
M
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* Presented before the Division of Chemical Education at the
eighty-fifthmeetingof the A. C. S., Washington. D. C.,March29, 1933.
t CARL J. ENoELDeR
AND WILL~AM S C ~ L L E"A R , system of qual~tativemicroanalysis," J. CHEM.Eouc., 9, 1636-44 (Sept.,
1932).
stances, the expenses are slight, the required apparatus colored adsorption compounds as proof of the presence can be blown by the student, and the danger inherent of magnesium; capillarity phenomena for an adequate to experiments with inflammable or explosive sub- separation of Cd from C d f ; and colored metallo-organic complexes for the detection of a great number of stances is greatly reduced. The benefits of experimental work a t home cannot cations. possibly be overestimated. I t must be clearly realized I have often wondered why the usual courses in that our usual laboratory courses can do very little qualitative analysis prescribe a definite set of nevertoward developing the student's imagination, initiative, varying elements, to the complete exclusion of elements and originality. Incessantly, he is assigned definite like selenium, beryllium, gold, etc. So far as I know, tasks and quite clearly he is told how to carry them out. the constitution of the United States does not prohibit He becomes so well trained in carrying out orders that the study of such an important element as titanium. when he starts his thesis work-which, theoretically Why then should bismuth be accorded a place out of speaking, ought to be an original contribution to sci- proportion to its importance? Since miaochemical ence--he is nothing but a perfect soldier, wd-disci- work requires very minute quantities of substances, it stands to reason that the expense of certain rarer metals, plined, but without any initiative of his own. Let us now consider in sharp contrast to this picture such as platinum, palladium, gold, etc., need not enter that of the field of the mechanical inventions. The into consideration. Why not test for elements as great achievements of the Americans in this field are they occur naturally, in minerals or in their industrial well known and are unequaled. This is due, we believe, applications? We believe that the student is more to the simple fact that most homes possess a work- likely to be interested in the analysis of the wire in an bench, thus providing innumerable boys with an op- electric light bulb than in the analysis of prepared salt portunity to give free course to their natural ingenuity. solutions. Consider the possibilities in this connection: I see no reason why the mechanical field should monopo- analysis of paint pigments scraped off in minute quanlize these precious and spontaneous gifts, once the home tities from an actual painting, or a metallic sample dissolved in a single drop of acid directly from an imporcan be equipped with a microchemical laboratory. Microchemistry, moreover, offers many possibilities tant alloy. Most textbooks on qualitative analysis stress certain in the training of our chemists in our colleges, most particularly in courses of qualitative analysis and in or- physical-chemical views to the exclusion of even eleganic chemistry. Educators are generally agreed as to mentary instruction concerning organic reagents. the superiority of micro methods where speed, accu- Since some of these are used, even in the most orthoracy, and a saving of materials are desired, but some dox courses, it is strange that advantage is not taken authorities claim that the student gains less in knowl- of this unique opportunity to familiarize the student edge through these methods than through the classical with some typical organic compounds. And why not procedures. Professor Engelder has met this objec- also use the sensitive and beautiful reaction of nickel tion by adopting a micro scheme which includes the with dimethylglyoxime as a starting point for a thoressential features of the usual classical methods of ough discussion of Werner's theory? Even within the boundaries of plain macro-analysis separation and identification of cations and anions. All the operations are carried out on a micro scale, and the trend is toward the adoption of the more sensitive the specific colored spot tests are used only as a means and specific organic reagents. Fresenius, the great old of final identification. As much as I admire Engelder's master of analytical chemistry, has predicted that evencontribution, I nevertheless think it would be more tually our time-consuming separations will be completely satisfactory to stress the best features from the proce- discarded. In the face of this evidence it seems predures of Gutzeit or Heller. Thus the cations would be posterous that the textbooks should continue overseparated only into large groups and then tested for emphasizing the ionization theory and solubilitydirectly by means of specific color reagents. For ex- product principle. While it is readily granted that this emphasis is a ample, in testing for copper in the presence of Bi, Pb, and Cd, we would take advantage of the specific color healthy reaction to the merely descriptive educational ways of former days, one wonders whether it is a pure reaction with benzoinoxime. This scheme furnishes the student with a really ade- and unadulterated blessing. Does it not possibly quate tool for analyzing a mixture of simple elements, kill the curiosity of the student and give him the impresand the time saved can be used for greater emphasis sion that there is a ready-made answer to every quesupon the so-called "preliminary experiments" in in- tion? Did not the famous phlogiston theory slow down creasing his knowledge of the chemistry of the elements the advancement of science for about a hundred years under study. The customary preliminary experiments simply because it was such a perfect theory that it are very uninteresting, while those in microchemistry answered all questions, and the chemist thought it involve a large number of reaction types which are im- superfluous to consult the experiment itself? Under pressed much more forcibly on the mind of the student. the circumstances it is easily explained why our average For example, a catalytic reaction is used in the detec- student seems to hold the belief that inorganic chemistion of thiosulfate; production of fluorescence to indi- try is a sort of petrified science as exhausted and dead as cate the presence of aluminum; formation of strongly Euclidean geometry. In an attempt to fight this atti-
tude and in order to inject more curiosity and enthusiasm into the student's mind I would intentionally stress the more controversial and growing aspects of inorganic chemistry. It is possible to do this and still remain quite within the circle of the experimental material as studied by the student in the laboratory. With the frequent use of filter paper for many of the
colored spot reactions the occasion is offeredfor discussing capillarity phenomena. The fascinating test for sulfide with the NaN3 I, mixture would provide the opportunity to speak of catalysis. Special attention should also be given to certain aspects of surface phenomena as far as this interesting new outgrowth of our science has a bearing upon analytical problems.
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