Popular Science Monthly/Volume 34/March 1889/The Chemistry of To-Day
|THE CHEMISTRY OF TO-DAY.|
PROFESSOR OF CHEMISTRY IN JOHNS HOPKINS UNIVERSITY.
SOME years ago, in the course of a conversation with an eminent mathematician, I asked in all seriousness whether he could give me a definition of mathematics that would convey to my mind even a faint idea of the object in view in mathematical investigation. He replied, "It is impossible to give such a definition—as impossible as it is in the case of chemistry." "But," said I, "I think I can give a definition of chemistry which would have some value"; and then, with little time to think, I suggested a definition, which elicited this remark: "I could certainly give an equally bald definition of mathematics." I have frequently thought of this subject since, and have wondered whether it is possible to convey to the minds of those who are not chemists a clear idea in regard to the work chemists are doing. The difficulties are great—as great, I suppose, as in the case of mathematics; for chemists are no longer engaged in the study of familiar phenomena, but are dealing with matters which lie far beyond the limits of ordinary observation. Still, I have thought it worth while to make the attempt, and it has seemed to me that I might accomplish my object best by calling attention to a few of the most important discoveries which have recently been made in the field of chemistry, and making such comments upon them as may serve to indicate what relations exist between these discoveries and the science as a whole.
Chemistry may be defined as that branch of science which has to deal with the changes in composition which the various forms of matter undergo. Not only has it to deal with these forms of matter, but also with the changes—that is, the acts involved in passing from one form to another. However bald this definition may appear to those who do not understand the subject, it is full of suggestion to the chemist. A chemist is sometimes spoken of as "one whose business it is to tell what things are made of." I accept this statement as expressing half the truth, but I attach to the words a much deeper meaning than they are intended to convey. To illustrate what I mean by this, let me take an example or two. Suppose a chemist is given a piece of marble. On examining it he finds without much difficulty that it is made of the forms of matter called carbon, oxygen, and calcium. He can also tell without much difficulty in what proportions these substances are present in the marble. He may thus tell what marble is made of. But is that all? May we not ask further what are the substances carton, oxygen, and calcium made of? It is true we call them elements or simple substances, meaning by that substances which can not be converted into anything simpler. No matter what influences the so-called elements are subjected to, they can not at present be decomposed. When, therefore, a chemist, after examining any complex substance, is able to say what simple substances are in it, he tells what it is made of. But, I repeat, is his statement final? Is there nothing more to learn? Plainly the great questions still remain to be answered: What is an element? Are the forms of matter which we call elements absolutely independent of each other, or are they not in turn composed of still subtler forms of matter which we may hope to discover in the future?
While it is impossible to answer these questions at present, some discoveries have been made within the past few years which have a direct bearing upon them. It has been shown by a Russian chemist, Mendelejeff, and at the same time by a German, Lothar Meyer, that the elements are related in a very remarkable way, so closely that it is possible to arrange them all in one table, in which they form parts of a general system. The law governing the variations in properties of the elements is known as the periodic law. The limits of this article will not permit any detailed explanation of this remarkable law. The main point that I wish to emphasize is, that these so-called elements are shown to be related to one another, and it seems impossible, in the light of these facts, to believe that they are distinct forms of matter. It seems much more probable that they are in turn composed of subtler elements, and it has been pointed out that all the substances which we now call elements, of which there are about seventy, can be conceived to be made of two fundamental elements combined in different proportions. There does not, however, appear to be any immediate prospect of discovering these fundamental substances, though we can not, of course, tell what a day may bring forth. While the prospect in this direction is not promising, it appears clear that there are other elements of the same order as those now known yet to be discovered. When Mendelejeff first arranged the known elements in his table, he found that the table was not complete, and it became necessary to leave certain places vacant in order to secure a perfectly systematic arrangement. It was as if an incomplete skeleton of some great animal were found. On putting the parts together, the finder would discover that something is wanting to complete the whole, but nevertheless he would recognize the relations between the parts before him. He would also be able to tell what the general properties of the missing parts must be. So here, the discoverer of the periodic law recognized that the system was incomplete. He pointed out the gaps, and prophesied the discovery of elements then unknown which would fill these gaps. Not only this, but he boldly ventured to describe some of these unknown elements in detail. At first no one was inclined to give serious consideration to the predictions; certainly no one dreamed that they would soon prove to be among the most brilliant predictions ever recorded in the annals of science. Within a few years all three of the elements predicted by Mendelejeff were discovered—the last one about two years ago. The first one was discovered in France, and was hence called gallium; the second, discovered in Norway, is known as scandium; and the third, recently discovered in Germany, is the baby element germanium. The descriptions given by Mendelejeff, eighteen years ago, are found to agree marvelously well with the facts. These discoveries have directed the attention of all chemists to the periodic law, and have lent a new interest to the discovery of new elements. There are undoubtedly others still undiscovered. Let us hope that the next one may come to light in the New World, and that we may thus have our own particular element, as France and Norway and Germany have theirs.
It is obvious from what I have already said that, to tell what things are made of, is not so simple a matter as it might at first appear. The best answer we can give, in any case, is lamentably incomplete. But there is another side to the subject, one of fascinating interest. Let me endeavor to illustrate this by means of another example. It has long been known that there are two substances, called respectively glucose and levulose, which are made of the same elements, viz., carbon, hydrogen, and oxygen, in exactly the same proportion by weight. Notwithstanding the fact that these two substances have exactly the same composition, they have markedly different properties. Chemistry abounds in similar examples. To account for these facts, chemists suppose that the parts of which the two substances are made up are arranged differently. An immense amount of work has been done during the past half-century with the object of reaching conclusions concerning what is called the constitution of chemical compounds, and the results reached in this field have been brilliant in the highest degree. By methods of the most refined character the chemist of to-day is enabled to enter into the innermost recesses of compounds, and trace out the connections which exist between the constituent parts. Many of the most complex compounds found in nature have thus been studied, their constitution determined, and methods have in many cases been devised by which the substances found in nature can be built up in the chemical laboratory without the intervention of the life process. Among recent achievements in this direction I may mention indigo. This is remarkably complex, and for a long time it had baffled all efforts to determine its constitution; but, finally, that prince of experimenters, Baeyer, of Munich, succeeded, and indigo is to-day manufactured from inert matter; and, though this manufactured article can not yet successfully compete with that obtained from the plant, it is, in my opinion, simply a question of time when the occupation of the plant will be gone.
The subject of the constitution or structure of chemical compounds at present receives more attention from working chemists than any other, and this has been the case ever since chemistry came to be a science. Great progress has been made, particularly within the past twenty or thirty years. In this field, as in that of the elements, to which I have already referred, wonderful predictions have been made and verified. Let me here quote a passage from an address by that eminent physiologist and philosopher Emil Du Bois-Reymond. He says: "I know of no more astonishing production of the human mind than structural chemistry. To develop, from that which appears to the five senses as quality and transformation of matter, such a doctrine as that of the relations between the hydrocarbons, could scarcely have been easier than to develop the mechanics of the planetary system from the motion of luminous points; and Strecker's prediction of the synthesis of creatine, which was afterward verified by Volhard, although in a less exalted sphere, was in fact no smaller achievement than the discovery of Neptune."
Of late, attempts have been made to go still further into the subject of structure, and to get some clew as to what we may call the actual shape of the minutest particles of which all forms of matter are believed to be made up. According to the prevailing theory, every kind of matter is made up of certain minute particles called molecules, and these molecules are conceived to be made up of still smaller particles called atoms. This theory is not merely a wild suggestion of dreamers, but it is forced upon us after a profound study of an immense number of facts. It is found that the facts can be explained only on this assumption. In chemical compounds it is believed that the atoms of elements are united with one another to form the molecules, and that the compounds are made up of these molecules, which are moving around freely in the case of a gas, less so in a liquid, and held together in solids. Now, the problem of the chemist is to determine how the atoms are arranged in the molecule—or to determine what connections exist between the atoms, without reference to the actual arrangement in space. When we consider that the atoms and molecules are almost infinitely small—so small, indeed, that we are told that the smallest particle of matter visible with the help of a good microscope must contain from sixty to one hundred millions of molecules—it does seem in the highest degree presumptuous to make any statement in regard to the way in which the atoms are connected in the molecules. Yet this is just what the chemist of to-day does, and the results accomplished by working in the way referred to fully justify him. Let no one to whom the facts are unknown accuse him of indulging in useless speculation. Chemical hypotheses are for the use of chemists; and so long as they are helpful, so long as they lead to a clearer and clearer recognition of the great truths of our subject, so long as they lead us on to work, and the science grows in consequence, it is not pertinent to remark that there may possibly be a flaw somewhere. If there are flaws in chemical hypotheses, they will be recognized by chemists themselves sooner than by others. Let no one think that science has nothing to do with the realm beyond the senses. Without the aid of the imagination there could be no science. However important they are, facts alone could not constitute a science. It is necessary that the relations between these facts should be discerned, and this can not be done except by the aid of the imagination. There have been few bolder flights than those which pertain to matters of science. The greatest genius is he who sees furthest beyond the facts, and with the aid of his imagination is able to bring together into a harmonious whole those facts which seem least connected. But, it must be remembered, it is the imagination of the thoroughly trained mind, kept in subjection by profound knowledge, that leads to great results.
I have said that of late attempts have been made to learn something of the shape of molecules. Within a few months a remarkable paper, written by Prof. Wislicenus, of the University of Leipsic, has appeared, in which the actual arrangement of atoms in the molecules is seriously and brilliantly discussed. I can not even touch upon the contents of that paper. Suffice it to say that chemists generally are profoundly interested in the arguments of Wislicenus, and the subject is now under active discussion. To me it appears that the views put forward are well worthy of most serious consideration. What the outcome will be, none can predict; but, at all events, the fact is significant that chemistry has reached a stage when such a subject can be discussed.
Another subject which is coming to the front in chemistry is that which I had in mind at the beginning of this article when I said, "I accept this statement as expressing half the truth." It is unquestionably the chemist's business to tell what things are made of, but the other half of the truth is this: it is also his business to study the chemical act itself. In any given case he must not be satisfied when he has learned that when two substances, A and B, are brought together, they combine to form the new substance, A B, He must study that act of combination, and learn all he can about it. As these acts in most cases take place almost instantaneously, this kind of study is exceedingly difficult. Nevertheless, some progress has been made within the last few years, and the number of chemists who are taking up work in this field is rapidly increasing. They are investigating such matters as the speed of chemical action, the influence of mass upon chemical reactions, and the relations between the phenomena of heat and electricity and chemical action. The best results have come from Russia, Sweden, and France. This branch is frequently referred to as physical chemistry. A number of books treating the subject have recently appeared, and a journal devoted exclusively to it has been started within the past year.
Now that I have begun to tell of the achievements of chemistry, I would fain continue; but, rather than run the risk of wearying my readers, I will turn at once to another subject, which I would gladly discuss at some length, but which I shall have to dismiss in a few words. I think I hear the remark: "This is all very well, but I thought chemistry was a practical science. What is the good of all these refined investigations on the nature of the elements and the constitution of chemical compounds? Can not the chemist find something more practical to work on?" These questions are constantly asked, and it is clear to me that they need answers. I take it that by the word practical is meant something which has a direct bearing upon our every-day lives. A practical investigation is one that leads to the establishment of some new industry, or it is one which leads to the discovery of some substance which can be used by man. My practical brother, then, has no sympathy with the kind of work I have been speaking of, but demands that the work should be of such character as to lead directly to results which can be utilized at once by mankind. It can not be denied that there is much that is reasonable in this demand. It is right that the results of scientific work should be made available, and that they should be utilized to the fullest extent for the improvement of man's condition. It is impossible to overestimate what we owe to chemistry, and we may confidently expect even greater gifts in the future than those which we have already received. Every year some new application of chemical discoveries is made. To whom do we owe the possibility of these applications? My answer is distinctly: We owe it to those chemists who are engaged in investigations in the field of pure science. Everything that tends to the perfection of the science of chemistry is of value in connection with the applications of chemical truths. The most refined investigation on the most abstruse chemical subject may furnish a link in a chain of argument—may be the one thing needed to lead to a most important generalization. The interests of the chemical industries and of the pure science of chemistry are identical. I do not ask that my assertion be accepted as final evidence on this point, I ask attention to the important fact that the seat of the great new chemical industries of the world is that country in which the greatest attention is paid to pure chemistry. As the result of much experience in Germany, it has been found that those chemists who are best versed in the pure science are the best fitted to go into the great factories and conduct the chemical operations. Even in the technical schools in Germany the subject of chemistry is taught just as it is in the universities, in such a way as to give the student as much as possible of the pure science. If my practical brother could make a tour of the great laboratories of the world, whether in universities or in polytechnic schools, he would find that the subjects under investigation in ninety-nine out of a hundred of them are such as he would regard as in a high degree unpractical; and yet I say the experience of the world has shown that, where the most of this unpractical work is done, there the most practical results are reached. The testimony of chemists is unanimous on this point. We are therefore led to the conclusion that the most unpractical work is the most practical—a conclusion which I am sure will stand the test of the closest examination.
But I do not think that this last argument is needed to justify the abstract chemical work of which I have been speaking. Man can be improved in other ways than by ministering to his daily bodily needs. He has higher needs, and some of these are ministered to by enlarging the world of ideas. Every discovery is an addition to the world's stock of knowledge, and we are all gainers by these discoveries. The gain is not as tangible as the material ones, but it is none the less valuable. Is not the world better off for its books, its works of art? Take them away. Imagine the result! So it is with the results of scientific work. By the aid of this work we are advancing toward clearer conceptions of the universe and our position in it. Stop the work, and intellectual death must necessarily follow. The work must go on entirely independently of the question whether the results can be utilized at once or not. We need more light! Let us work for this.