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Sir William Ramsay
(2 Oct 1852 - 23 Jul 1916)
Scottish chemist who was awarded the 1904 Nobel Prize in Chemistry for his “discovery of the inert gaseous elements in air.”
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How Discoveries Are Made
by SIR WILLIAM RAMSAY, K.C.B., F.R.S.
from Cassell’s Magazine, Illustrated (May 1908)
[p.629] THERE is a difference between discovery and invention. A discovery brings to light what existed before, but what was not known; an invention is the contrivance of something that did not exist before. I suppose, however, that inventions and discoveries are made in much the same manner; though I have no claim to speak as an inventor, except in a very small way. Many people, probably most people, think that when a discovery is made, it comes all in a flash, as it were—that a new idea suddenly crops up, and its conception is a discovery. That may sometimes be the case. We have all heard of the puzzle given to Archimedes; how he was asked to find out, without injuring it in the least, whether a certain crown consisted of silver or of gold; and by weighing it in air and in water, he invented the method of taking specific gravity; for the crown lost weight when weighed in water equal to that of the water which it displaced. And he ran through the streets of Alexandria, crying “Eureka! I have found it !”
Discoverers must be Inventors.
His finding that the crown was of gold was a discovery, but he invented the method of determining the density of solids. Indeed, discoverers must generally be inventors; though inventors are not necessarily discoverers. It is too often supposed that, like the poet, discoverers are “born, not made”; but I think I shall be able to show that many people, though not all, have in them the power of making discoveries; and if this short article can give to any one the hope of making discoveries, and prompt him to try, it will have more than achieved its object. Like every other endeavour, the beginning is in small things. Any one who tries to look into anything with sufficient care will find something new. A drop of water; a grain of sand; an insect; a blade of grass; we know indeed little about them when all is told. First, of course, we must learn what others have done; and for that purpose we go to school and to college, and read books and hear lectures. Before beginning, we should at least have an idea of what has been achieved by our predecessors. After that, there is nothing for it but to try.
But there are two ways of trying: and what I wish to convey is best told in an allegory.
Salmon or Sprats.
There are two kinds of fishers: those who fish for sprats and those who angle for salmon. I do not say there are not others; but these two kinds are at the extremes of the fishing world. The fishers for sprats are sure of a large catch, or at least of catching something; but the fish are small, not particularly attractive as food, and of no great value; they are, however, numerous and easily caught. But the salmon fisher hunts a very different prey; if there is any special quality about a salmon, it is his power of motion and his fickleness of taste; so that the angler, when he casts his line, is by no means sure that a fish is within reach of his cast, nor, if he is, whether he will rise to the fly. If fate is propitious, however, his prize is a great one; his pleasure consists not merely in catching the fish, but in struggling with him, possibly for an hour or more; wading after him in alternate hope and fear— hope that his line may stand the strain, fear that it may part, or that some hasty movement may lose him his fish.
Most discoverers are like fishers for sprats: they go where they are sure of a reward; but the gain is not great, at least as regards sport. It is much more fun to fish for salmon ; but then there is a great chance that the angler has mistaken the place to fish, or that he has used the wrong fly; or that the weather is unfavourable; or that a hundred things, impossible to foresee, will prevent the salmon taking the hook.
We may not pursue the allegory further; [p.630] salmon are now not nearly so plentiful as they used to be; sprats, perhaps even more numerous. And it requires training and a good eye to know where the salmon lie and in what pools to fish.
But let us dismiss this image and become historical. One of the first puzzles which awaited solution was the nature of flame. The ancients believed it to be an element—that is, a property, or perhaps a constituent of most, or of all, other things. Flame, said they, is hot; and everything which is hot partakes of the nature of flame.
Priestley and Schule.
Robert Boyle guessed that it was a sign of the rapid movement of the minute particles of which he supposed everything to be composed; but this, although very near what we now suppose to be the truth, was merely a lucky guess; for he had no real ground for making the suggestion. It was noticed that flame appears when anything burns; and the reason for combustion, or burning, had first to be sought. .
The real step towards this was made by Joseph Priestley, an English dissenting minister, and by Karl Schule, a Swedish apothecary, almost at the same time. Priestley was a fisher for salmon, to revert to our old image; he fished everywhere and caught many large fish. And so was Schule. They noticed that when certain substances were heated, gases—or, as they termed them, “airs”—escape. For it had been supposed that all gases, as we now name them, were merely modifications of ordinary air; just as we sometimes notice a pleasant or a disagreeable smell, and attribute it to the “goodness” or “badness” of the air, so it was generally thought that gases, such as coal-gas, were a sort of air with an unpleasant odour and the curious property of catching fire. .
About fifteen years before Priestley and Schule made their great discovery of oxygen, the constituent of air which supports combustion, a Scottish professor, Joseph Black, investigated the particular kind of “air” which escapes when chalk or limestone is heated. And he made the great discovery that this “air” can be reabsorbed by lime—the residue left after chalk is heated—so that chalk is again formed. .
Moreover, he weighed the chalk before it was heated, he measured the gas, and he weighed the lime left after the gas had been driven off from the chalk. And lastly, he weighed the chalk which was re-formed after the lime had absorbed the gas. .
He found that the lime was lighter by just as much as the gas weighed; and he called this gas “fixed air,” to emphasize the fact that it could be “fixed “ or absorbed by lime and similar substances.
This first opened the way for the investigation of gases; it was a great discovery–perhaps one of the most fertile which has ever been made. It is to be noted that Black was not content with this, however; for he recognised that the fixed air from chalk was of the same nature as steam from water. And just as it is necessary to heat water so as to drive it into steam, so it appeared to him that carbonic acid gas, to give “fixed air” a more modern name, was a gas by virtue of the heat or “caloric” which it contained. And he went on to discover how much heat is required to convert a known weight of water into steam. He found that about fifty-four times as much heat is required as is necessary to heat the same weight of water from the freezing-point to the boiling-point. But the steam is no hotter than the boiling water; hence Black called this heat the “latent heat “ of steam, because it lies hidden in the steam and does not affect a thermometer. Black made quantitative experiments—that is, he not merely made discoveries, but found the quantities in which the changes took place.
Making the Way Plain.
The way was now plain for Priestley and Schule. They heated all kinds of substances: if they evolved gas, that gas was collected and examined; but neither Priestley nor Schule paid much attention to quantities. The methods of dealing with gases had to be invented, moreover. And while Schule caught his gases in bladders, Priestley invented, of rather re-invented, what he called a “pneumatic trough,” a vessel filled with water containing jars and bottles standing [p.632] inverted full of water. If the tube leading from the retort in which the substance evolving the gas was heated was directed so that its open end was directly under the mouth of the bottle, the escaping gas entered the bottle and displaced the water; and when the bottle was full, it could be corked, still under water, and removed so that the gas could be examined.
Discoverer must be a Handyman
It is usually the case that discoveries have to be accompanied by inventions; the sequence is that to try any new thing, a piece of apparatus has to be devised which will effect the purpose—or perhaps an apparatus already known has to be altered—so that it may almost be said that invention and discovery go hand in hand.
For this reason it is very important that the discoverer should be a good worker in all kinds of materials—in glass, for most small pieces of apparatus can best be constructed of glass; in brass, for if anything of the nature of machinery, such as pumps, stirrers, etc., is required, brass is perhaps the most convenient material; in clay, for vessels are wanted which will withstand a high temperature; and of recent years silica glass, made from fused rock-crystal, is of great use, for it can be worked before a blow-pipe fed with coal-gas and oxygen.
But to return to the discovery of oxygen. Priestley heated oxide of mercury, or, as he called it, “red precipitate,” in a retort, and collected the escaping gas; and he found that a candle burned in it much more brightly than in air; and, moreover, after having found that a mouse could live in it longer than in the same volume of air, confined in a bottle, he breathed it himself and found that its effect was pleasant and exhilarating.
The Cause of Flame.
Similar experiments were made by Schule with the same result; but Schule went much further. Having noticed that a number of substances had the property of making combustible bodies, such as wood, flour, and charcoal, deflagrate, or burn more brilliantly when mixed with them, he heated these substances, and found that they too evolved oxygen gas. Among the substances were red-lead, black oxide of manganese, nitre, and many others; so he established a general rule that those substances which can be mixed with charcoal to make a kind of gunpowder will evolve oxygen when heated. .
It thus became known that air contained a gas, amounting to about a quarter— Schule says a sixth—of its bulk, possessing the property of making combustible objects burn with greater vigour. Flame, therefore, was caused by the action of oxygen, as the new gas was called later, with combustible bodies. .
It would take too long to consider the curious doctrine of “phlogiston,” an immaterial effluvium which was supposed to escape when bodies burn; I can merely mention that Lavoisier, a celebrated French chemist, gave the correct explanation of combustion—namely, that it is caused by the union of oxygen with the substance burning. Lavoisier, however, cannot be ranked as a great discoverer, though he shone as an interpreter of the discoveries of others.
What Water is Made of.
Henry Cavendish, who did his best work between 1770 and 1790, discovered the composition of water; that it is produced when oxygen and hydrogen unite; and he determined with the utmost accuracy the proportions by volume in which the union of the two gases is completed. He also attempted to show, by passing electric sparks through a mixture of the inert gas of the atmosphere, nitrogen, mixed with oxygen, that nitrogen was a single substance and not a mixture; nearly all the nitrogen disappeared under this treatment, only about one hundred and twenty-fifth of the whole being left. It would hardly have been possible for him, in the existing state of knowledge, with the imperfect appliances which alone were available at that time, to have identified his inactive residue with “argon,” a gas discovered more than a century later; for the spectroscope was then unknown, and it is the chief means of identifying and characterising gases, and indeed elements of every kind. This is an example of how discovery has sometimes to wait on [p.633] invention; for, until the instruments of research are invented, it is almost impossible to confirm a discovery, even although it may be genuine. .
The true nature of flame, which, as before remarked, has been a puzzle since the remotest ages, has had to wait on invention for its discovery. When a current of electricity of high tension, such as is produced by an induction-coil or by an electric machine, is passed through any rarefied gas, it gives out a peculiar and often a very beautiful coloured light: sometimes red, as in the case of hydrogen or neon ; sometimes bluish-white, as with carbonic acid or krypton; sometimes purple-red, as with argon or nitrogen. When examined through a prism or a spectroscope, this light is seen to consist of a number of colours, which blend to give the colour seen with the naked eye.
The Glow of Gas.
Thus the brilliantly red spectrum of hydrogen is easily shown to be a compound impression; the red light, which is the brightest, is mixed with and slightly modified by a blue-green and a violet light. Tubes which are well adapted to show this light were invented by a German physicist named Plücker in the ‘fifties. Twenty-five years later, Sir William Crookes, with the aid of his skilful assistant, Mr. Gimingham, improved the then existing form of air-pump, invented by Dr. Hermann Sprengel, so that it became capable of exhausting the air much more completely than was previously possible. .
He found that, at a much greater exhaustion than that which causes gases to glow and give out their spectrum, a current of high-tension electricity produced in the tube a violet or a green phosphorescence, according as the glass of which it was made contained lead and potash, or lime and soda, combined with the silica, or sand. .
Moreover, the position of this curious phosphorescent glow depended on the shape and direction of the wire or plate from which the negative electricity passed into the tube. From a wire the glow proceeded in all directions perpendicular with its length, so as to colour the tubes immediately surrounding the wire with phosphorescent light.
If the wire, however, were terminated with a plate, then the phosphorescent light appeared mostly between the front of the plate and the positive wire of the vacuum-tube. Supposing the plate were curved, so as to form a concave metallic reflector, the line of what was evidently a discharge was concentrated on a point at the focus of the metallic mirror.
Moreover, if an object of any kind were placed at the focus, and submitted to the discharge, it became intensely hot; or if it could move—if, for instance, it formed the vanes of a little wheel or windmill—the wheel revolved rapidly as if it were being bombarded by infinitesimally small bullets. Crookes imagined that by being thus highly rarefied, the gaseous matter changed so as to become “ultra-gaseous,” that it changed its state in somewhat the same manner as ice becomes water or as water becomes steam.
New Elements.
It is interesting here to recall how Sir William Crookes came to make these most remarkable discoveries. He began by using a spectroscope to investigate the spectrum—or coloured light given out by the various constituents into which he had analysed the dust—which deposits, in the flues used to convey the sulphurous acid produced by the burning of pyrites, a compound of sulphur and iron, then (in the ‘sixties) recently introduced as a source of sulphur for the manufacture of sulphuric acid or oil of vitriol. One of his precipitates, when examined with the spectroscope, showed the presence of a bright green light; and this was traced to the presence of a new element, to which he gave the name “thallium,” from the Greek “thallos,” a green twig. .
One of the first things done with a new element is to try to discover its “equivalent”—that is, the proportion by weight of the element which will combine with 8 parts by weight of oxygen. (The number 8 is chosen, because 8 parts by weight of oxygen combine with 1 part of hydrogen to form water.) The weighings require to be very accurately made; and a peculiarity which affects all attempts to weigh very accurately must now be told of. The question is often asked as a catch —”Which weighs most: a pound of [p.634] feathers or a pound of lead?” The usual answer is, “They weigh the same.”
Although this is strictly true (for a pound is a pound, whether of lead or feathers), a little consideration will show that when the feathers are placed on one pan of a pair of scales and the lead on the other, the lead takes up far less room than the feathers; in other words, the feathers displace much air, while the lead displaces little. That is, the air which the feathers displace no longer rests on the pan; and if it were still there, the feathers would weigh more. Hence a so-called pound of feathers weighs less than it ought to by the weight of the air displaced.
Now, to overcome this difficulty and to avoid the somewhat complicated and uncertain calculations necessary to ascertain the true weight of the things weighed, Sir William Crookes devised a balance closed in by a case in which a vacuum could be made. And it was while obtaining this vacuum that he discovered that light apparently (but really heat) appears to repel certain objects more than others. And so he was led to experiment on vacuum-tubes and to perform all the beautiful experiments which have made his name so famous. At the same time he invented the “radiometer,” a pretty little toy for showing the repelling action of heat.
Bent by a Magnet.
Here again we see the advantage of following up small trails; they may widen to great and most important roads. If Sir William had been content to weigh his compounds of thallium in his vacuum-balance, as most others would have done, and had not had the genius to follow this side-track, he would have missed many of his greatest discoveries. A further great step was made when the German physicist Lenard found that Crookes’s “rays”—the “fourth form of matter” which he supposed to be repelled from the negative pole of the Plücker tube when very highly exhausted—could pass out of the tube through a thin “window” of the very light and strong metal aluminium. It is true they could not pass very far; they soon became scattered. Here was a discovery made with a set purpose. Professor Lenard wished to decide the question whether Crookes’s “rays” were really due to a stream of corpuscles or whether they were vibrations like those of light. Sir William had previously found that if a magnet were placed near the tube the path of the rays was no longer straight, but curved. And Lenard observed that if the aluminium window were placed so that a “vacuum” (not a complete, but a nearly complete one) were on both sides of the aluminium window, the “rays” could be bent out of their course by the magnet after passing through the window.
Röntgen’s Luck.
It must be remembered that these rays are not themselves visible; it is only possible to see where they strike by their causing phosphorescence. Professor Röntgen, the celebrated German physicist, discovered in his turn that if these rays be suddenly stopped—say by falling on glass or metal—rays of another kind are sent on, which have the power of affecting a photographic plate and of rendering certain substances exposed to them phosphorescent; so that, as different kinds of matter have very different powers of stopping Röntgen rays, it is possible to photograph the bones of the body, although the flesh is comparatively transparent to them. The bones, as it were, cast their shadow ; or the shadow of the bones can be thrown on a piece of card, painted with material which phosphoresces and shines when exposed to their impact.
I believe that Röntgen’s discovery arose from an accidental observation that a box of photographic plates left near a Crookes’s tube became “fogged,” and that he too had genius to follow up this clue.
We are getting on rather slowly, however, in the hunt for an explanation of flame. A great step in advance was made by the discovery of radium by Madame Curie.
What is Radium?
Radium is a metal, the salts of which continually give out “Lenard rays,” or “Crookes’s rays.” And it is certain that it is losing substance during their emission. Mr. Soddy and I have actually trapped and measured one of the products which is being thrown off by radium while these [p.635] rays are being shot out; it is a gas called “radium emanation.” And it in its turn decomposes and is changed to some extent into the gaseous element helium, which I discovered in 1895.
All the while that these changes are taking place, what are called “B-rays” (beta-rays) are being evolved, and the opinion is now generally held that these so-called rays are really negative electricity, and are identical with the “cathode-rays” of Lenard.
I have been frequently asked: “But is not electricity a vibration? How can wireless telegraphy be explained by the passage of little particles or corpuscles?” The answer is “Electricity is a thing; it is these minute corpuscles, but when they leave any object, a wave, like a wave of light, spreads through the ether, and this wave is used for wireless telegraphy.”
It has been found that flames are capable of conducting electricity, while gases, under the usual atmospheric pressure, are very good insulators, and sparks can pass through air only when the current is one of very high tension. Now, in flames rapid chemical action is taking place; compounds are burning—that is, their constituents are in the act of uniting with oxygen.
“B-Rays.”
Although it is not certain that B-rays– or, to give their other name, corpuscles of electricity—are being shot out during such changes, it is not improbable that they are. No doubt they impinge on the neighbouring atoms and set them in rapid vibration; and they may even break up molecules and cause them to assume other forms of combination. And in doing so, very short electric waves are sent out through the other, and these are what we term “light.” .
There are several other lines of evidence which support this notion. For example, a pure gas cannot be heated red-hot or made to glow by heat alone. There must be a chemical change of some kind at the same time. Again, a Welsbach incandescent gas mantle, if made of pure thoria (and that means “nearly pure,” because we are not acquainted with really pure substances), does not give out much light when heated, but if some other earth, such as oxide of cerium, is mixed with the thoria, the familiar brilliant incandescence is produced when it is heated by a Bunsen burner. The “pencil” of a Nernst lamp is made chiefly of zirconia, another earth; and here, again, unless the zirconia is mixed with a trace of some other oxide, it will not glow very brightly when a current of electricity is passed through it. In all these cases there is almost certainly chemical change and also, no doubt, evolution of corpuscles of electricity which set the ether vibrating and so produce light.
Shooting Corpuscles.
It may be asked: “Do substances not lose weight when corpuscles are being shot out?” Professor Landolt, of Berlin, has been making experiments on the gain or loss of weight when a weighed quantity of substances capable of chemical change are mixed in a closed vessel; and he finds that in many cases there is a minute loss of weight. Perhaps that is due to the escape of corpuscles; but too few experiments have been made to allow of a definite answer.
Perhaps, too, the corpuscles when expelled are not moving very rapidly and are thus absorbed by the sides of the vessel in which the reaction takes place; and this may also be the case with flames. A flame, however, if brought near an object containing an electric discharge will discharge it; and this is in all probability due to the action of electric corpuscles on the charged object. It will be seen, then, that we do not know yet with certainty what flame is, but we are getting on the track. And the direction in which to make experiments is clear. Whoever asks shall receive, but he must ask sensible questions in definite order, so that the answer to the first suggests a second, and the reply to the second suggests a third, and so on. If that course be followed, it will certainly result in discoveries, many of which may be important and lead to inventions of great practical value. For, indeed, an invention is often definable as a method for utilising a discovery.
- Science Quotes by Sir William Ramsay.
- 2 Oct - short biography, births, deaths and events on date of Ramsay's birth.
- Radium and its Products - by William Ramsay in Harper’s Magazine (Dec 1904).
- The Early Days of Chemistry - by William Ramsay, Collected in Essays Biographical and Chemical (1909).
- Air: Scientific Discoveries and Inventions - from Haydn's Dictionary of Dates (1904).
- A Life of Sir William Ramsay, by Morris W. Travers. - book suggestion.
