THE METHODOLOGY OF SCIENTIFIC RESEARCH* HENRY M. LE CHATELIER. FACULTY OF SCIENCE. UNIVERSITY OP PARIS, PARIS,FRANCE
It is difficult a t first glance to account for the varying success of the . men of apparently equal endowments and training who have devoted themselves to scientific research. Consequently, it seems worthwhile to seek out the reasons underlying the success of those men of genius who have become eminent in science. First and foremost is the gift of obserwation, that is to say, the faculty of fixing one's attention on facts which appear unexpectedly. Some workers notice everything which occurs during their experiments, while others observe nothing. Lord Rayleigh noted the discordance in the density of nitrogen derived from the air and that prepared chemically, and was thus led to the discovery of the rare gases of the atmosphere. Other scientists had been confronted with this discrepancy but had given i t no attention. Lavoisier placed iron filings in water and noticed the continuous liberation of a . small number of minute bubbles, an observation that resulted in the discovery of the composition of water. Auer von Welsbach while calcining precipitated thoria was struck by the exceptional glow emitted, the Welsbach mantle resulted; others had seen the same thing but i t had not arrested their attention. This faculty of keen observation is partly a natural gift that is usually inherent in those of impressionable temperaments, but it may also be developed by proper methods of education. Chemical manipulations involving the actual handling of materials are of great value here. For example, a stolid pupil may be told to &at a small quantity of iodine in a test tube and to describe all that he has seen. He ought to have seen the violet vapor, the black sublimate, the deposit of small crystals on the colder parts of the tube, and so on, but how many of these details will he actually have noted? A group of children may be sent to a given point in the country with instructions to observe their surroundings. On their return one will have seen only the hills, another, a ditch by the road side, a third, a church steeple. A second quality essential in scientific research is the association of ideas, that is, the ability to bring together a t a desired time the enormous number of facts which have accumulated in the memory but which it is very . difficult to recall a t the opportune moment. It is sometimes said that a document that has been filed and classified is likely to remain buried until the end of time. The same is partly true of the memory from which a t the desired moment only a small fraction of the material stored there may be recovered. Men T i e r greatly in this respect. The writer remembers with great interest a conversation he overheard between Berthelot and one of his assistants. The latter had been ordered * Translated by Ralph E. Oesper, University of Cincinnati, Cincinnati, Ohio. 2584
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to analyze an antique bronze and Berthelot was inquiring as to his findings. The assistant reported that the bronze contained 6% of tin, and Berthelot asked how he had identified the tin. "After treating the sample with nitric acid the addition of sulfuric acid produced a white, insoluble precipitate." Berthelot said, "Do you not know that lead sulfate is likewise white and insoluble?" "Yes, but I did not think of that." "Have yon tried the action of ammonium sulfide on your precipitate to be sure that it "I did not think of that." "Don't you know will not turn black!" that most antique bronzes do not contain tin, but rather lead; haven't you already analyzed several samples of these?" "Yes, but I was no longer thinking about those." In this instance Berthelot and his assistant had exactly the same knowledge available in their memories. In ten seconds, Berthelot recalled the facts and used them, while the assistant, after eight hours of work on this same problem, recalled nothing pertinent to the analysis. Another example, Long before Lavoisier it was known that metals increase in weight when calcined in the air. Pascal's experiments with the barometer had shown that air has weight. However, no one dreamed there was any connection between these two facts until Lavoisier did so and thus laid the foundations of modern chemistry. Likewise, the impossibility of perpetual motion was recognized long before Sadi Carnot, as was the possibility of converting heat into work. It remained for him to unite these two ideas and so create the science of energy. This ability is not an innate quality, for childven do not possess it, and its acquisition is one of the essential aims of education. Accurate Latin translation, the writing of orations, and the solution of geometrical problems are typical of the subjects best calculated to develop the faculty of using knowledge previously acquired. A final aptitude, not usually considered in relation to scientific research, although of prime importance, is common sense: that is, that faculty which Pascal termed the "sense of $nessen (intuition) as opposed to the "sense of geometry" (strict logic). It is but seldom that one can give his exact reasons for a certain lime of conduct. Sometimes one's knowledge of the primordial facts is insufficient to construct a line of reasoning, but more often one is confronted by diierent points of view which lack common factors and which consequently cannot be treated by the customary methods of reasoning. First of all, common sense plays an important r81e in the choice of a life work. To become a great scientist it is not sufficientto have been a good experimenter. It is essential that the field of endeavor be of importance, either from the point of view of advancing theory, or of developing public wealth or the general welfare of mankind. Examples of the first class are Fresnel's study of the theory of light, Sadi Carnot's investigations of the
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motive power of heat, Berthdot's researches on organic synthesis, and St. Claire Deville's work on dissociation. Instances of the more immediately practical are the work of Gay-Lussac on the manufacture of sulfuric acid, the liquefaction of air and the synthesis of ammonia by Claude, incandescent gas lighting by Auer, improvements in the candle industry by Chevreul, chlorine bleaches by Bertholet, the electric furnace by Moissan. Obviously there is need of workers to study and cultivate all the narrow corners of science, but they cannot hope to achieve the same fame as those who open new realms into which they are followed by numerous workers content to do the conventional routine tasks. Those scientists who are wise enough to recognize what Taine, in the field of art, called the "dominant characteristics" are almost certain to produce work of superior importance. Common sense plays a second very important part in the choice of the hypotheses which serve as a starting point for the majority of scientific researches. It is often stated that a man may make whatever hypotheses he pleases, that these may even be absurd and yet yield interesting conclusions, provided that he follow meticulously the rule of Claude Bernard: "Subject every experiment to rigid control and abandon a hypothesis ruthlessly as soon as a single definitely established fact does not conform to it." But it is certainly true that a judicious selection of hypotheses will lead more rapidly to useful results with economy of labor and with increased efficiency. When St. Claire Deville, having fowd that the temperature of the oxy-hydrogen flame was much lower than expected, postulated that the combination of hydrogen and oxygen was not complete, his choice of possible explanation was a wise one and its verification resulted in the very important discovery of the phenomenon of dissociation. Pasteur made an equally judicious choice when he presupposed that no living thing could develop spontaneously. He might have assumed the contrary to be true and yet have reached the same concIusions after having learned from experiments that his supposition was incorrect. This, however, would have involved much more labor before a definite conclusion could have been reached. I t was a long time before his adversaries, who maintained the opposite view, admitted the facts. A third r81e of common sense is involved in the interpretation of experimental findings. Great difficulty arises from the errors which all measurements inevitably include. Instead of recognizing this fact, experimenters sometimes allow themselves to be drawn into absurd conclusions by regarding experimental errors as new properties of matter. Classic examples may be cited. Schutzenberger announced that atomic weights are not constant, basing this conclusion on analyses of benzene which did not agree with each other. He was not aware that carbon dioxide had passed through
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the walls of the excessively long rubber tubes of his apparatus. Sir William Ramsay believed that he had transmuted silicon into carbon, and copper into lithium, but later realized that the carbon actually came from the grease on his stopcocks, and the lithium from the glass of his apparatus. Hiurichs thought he had proved that the atomic weights of all the elements are whole numbers, a conclusion arising from the erroneous use of algebraic functions. Carvallo deduced from Becquerel's work on the dichroism of crystals that Fresnel's theory of light was inexact. In reality, this disagreement did not reside in the experimental facts but in the algebraic form of an empirical interpolation formula incompatible with Fresnel's theory. Numerous other empirical formulas which represented equally well the experimental results of Becquerel all agreed with this theory of light. Recently, Ernst Cohen has questioned the findings of Mondain Monval on the variation of the solubility of ammonium nitrate a t its transformation point and has stated that these are not in agreement with his own figures. As a matter of fact, the disagreement arises only from the arbitrary choice of interpolation formulas. Cohen evidently neglected to take into consideration the fact that curves which would represent equally well the experimental points might have tangents of different slopes, especially in the portions extrapolated beyond the experimental region, as really was the case. On similar grounds, a great many of the pronouncements of modern physics ought to be closely smtinized, especially those which deal with radioactivity, isotopes, the velocity of light, the $istribution of colloids at various levels, and so on. The urge to find new facts and especially those that apparently contradict the accepted data seems, in many instances, to have paralyzed the critical sense of those who write on these topics. Common sense also plays a very useful r81e in the establishment of scientific theories and in the coinage of the new terminology necessitated by them. Only too often is i t necessary to guard against the useless complications and obscure terms that needlessly burden science today. For example, the expression "false equilibrium" is quite current though it is thoroughly contrary to good usage. A chemical system is either in equilibrium or it is not; false equilibria do not exist. The origin of this bizarre expression is due to Duhem. While a student a t the !hole Normale he gave a short account of the important work of J. W. Gibbs on the equilibria of heterogeneous systems, which, however, he did not understand very well. In translating the passage dealing with passive resistance or chemical inertia, he considered the absence of reaction as a necessary and sufficient characteristic of equilibrium. In reality, the state of equilibrium is defined by the double condition that the system does not change spontaneously and that this transformation toward either side may be brought about by an inhitely small expenditure of energy. His error
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was pointed out to him, but instead of frankly admitting that he was wrong, he tried to gloss over his mistake by inventing the new term, "false equilibrium," for such systems as are not in equilibrium and which, however, persist unchanged by reason of chemical inertia. Another example. All the statements of chemical mechanics applied to systems of solutions are based today on considerations involving osmotic pressures. This tradition is solely justified by respect for the authority of van't Hoff; the small pamphlet of Pascal on the authority of factual knowledge of science seems to have been thoroughly forgotten. The very existence of osmotic pressure is debatable, and it is impossible to measure these pressures accurately. They can only be used if they are related to the vapor tensions of solutions by means of a very simple formula due to van't Hoff himself. Innumerable and very exact measurements of vapor tensions are available, and precisely the same lines of reasoning may be followed employing these tensions as are used with osmotic pressures. Consequently there is no valid reason for not adopting this method. However, the expression "osmotic pressure" is so thoroughly rooted that many chemists would find it difficult to follow a discussiou in which vapor pressures had been substituted for osmotic pressures. It was the same when Lavoisier demonstrated the non-existence of phlogiston. The chemists of his time did not question the accuracy of his experiments, but they declared that they could not understand a chemistry in which the word phlogiston did not occur because it was the medium in which they were accustomed to think. E Likewise, all the actual theory involving pH will perhaps profit, if the concentration of that fictitious entity known as "hydrogen ion" is replaced by the product of two conaete values: the concentration and the strength of the acid, the latter being measured by the equilibrium constant of the acid against a given standard salt. Very probably, the future will see marked changes in the theories as to the electrolytic composition of solutions, while the concentration and the strength of an acid are immutable magnitudes. Common sense is a most rare mental quality and is most difticult to acquire. Its development is one of the most important objectives of those studies known as the classical humanities. A curriculum involving nothing but science is very likely to warp the judgment by blinding the pupil to the fallacy of pure logic; literary studies in general axe much better in this regard because the diversity of moral and social phenomena which they present tend to familarize the mind with the complexity of the possible points of view. Almost all eminent scientists received an education which was predominantly literary. This was the case with Pascal, Descartes, Huygheus, Lavoisier, the Carnots (father and son), Ampere, Claude Bernard, Berthelot, etc.
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In conclusion, the writer wishes to stress the fact that the proper way to train scientists is not to overload the memory of students daily with information, in the belief that to develop a taste for science it is necessary above all to endow their intellectual faculties with a certain orientation and a certain diligence. This is an opinion formulated by the Greeks, for Plutarch said long ago, "The child's mind is not a vessel to be filled, but a fire to be kindled." Recently the American e5ciency engineer, F. W. Taylor, repeated this same thought in a slightly different form: "The child's mind should not be considered a sponge that one is content merely to saturate indiscriminately and uselessly for the sole purpose of accumulating information." Rew Drugs by Thousands Await Discovery. Never in the history of the world have the possibilities of adding to the list of valuable drugs been so great as a t the present time, Dr. Reid Hunt, president of the United States Pharmacopeia Convention and professor of pharmacology a t Harvard Medical School, declared a t the opening session of the convention's recent decennial meeting in Washington, We may yet,get more drugs from the plant and animal kingdoms. There is no limit t o the number that the chemist and the pharmacologist may synthesize in their laboratories. But even more important is the possibility that new and important uses may be found for drugs which we already have, IX.Hunt said. Some of the saddest pages in the history of mankind have written on them the failure of physicians t o see the possibilities for treating disease with well-known chemicals. Ether was known t o dactors and chemists for nearly 300 years before i t was used ss an anesthetic. Another drup, .amvl . nitrite, a few drops of which relieves the frightful . agony of one form of heart disease, was well known t o chFmists for 23 years before i t was used to treat this condition. The same delayed application was r e ~ e a t e din the case of other anesthetics and many other drugs. They were well kno- chemically for years before any one tried them in the treatment of disease and for the relief of pain. "Today, relief may be obtained anywhere in the world for a few cents, which fifty years ago w a s beyond the reach of any potentate or Croesus." Research is needed to investigate the medical possibilities of the 258,000 organic compounds which chemists have already carefnUy described chemically and physically, Dr. Hunt said. New compounds are being added to the list a t the rate of about twenty a day. He declared America's facilities for studying the medical applications of these new compounds are very inadequate compared with research activity in Germany and other European countries.-Science Service Ethyl Gas Approved for Use in Britain. Ethyl gasoline has been given a good bill of health in Britain, provided its handling is attended by ordinary precautions. The questions raised regarding its safety have been investigated by a Departmental Committee an Ethyl Petrol, which has just issued its final report. The committee worked along lines somewhat similar to those followed in the earlier investigations in the United States, and they took into consideration the results of the American experiments as well. The aspects of the tetra ethyl lead problem on the committee's agenda included danger from lead in street fumes and dust, spillage on the skin, and evaporation and combustion fumes in closed garages. Danger of lead poisoning in the latter ease was considered as considerably less than the well-recognized menace of carbon monoxide.-Science Sem'ce
