CONCERNING TWO OCEANS1 JOHN E. CAVELTI Allegheny College, Meadville, Pennsylvania
BEPORE THE coming 'of the atomic bomb it seemed certain that in some future time mankind would be compelled to learn the use of vast but dilute sauces of power--solar energy, wind power, tidal power. The tidy little chunks of concentrated solar energy represented by coal mines and petroleum pools will certainly not last indefinitely. Perhaps atomic fission will open up a new source of still more concentrated power in enough quantity, and perhaps not. In the realm of material things it still seems almost certain that the future will require the conquering of the dilute. With the assistance of world wars our concentrated ore bodies are being rapidly depleted. 'The exploitation of more dilute deposits may be left to the h i s t s and engineers of the future. Two dilute mrces of desired materials have, however, already been tapped-one of them dilute because of the nature of gases, the other because of the prevalence of water. They are our oceans, of two kinds. It is apparently difficult for the human mind really to believe that gases are an honest form of matter, having weight like the other forms and being as' respectworthy as they. Early man probably t h ~ u g h t ~ winds of as the ' manifestation of some sort of spirit, wheress waves, being visible motion in a tsngihle medium, seemed more understandable. Even the Greeks, who elevated air to the position of an element, did not th'mk of it as being real substance and having weight. Air was coupled with fire as a fine element, the two being somewhat contrasted with water and earth, the gross and somehow less worthy elements. It was not until 1600 A.D. that air was shown by Galileo to have weight. WE LIVE IN AN OCEAN We have often compared the conduct of our fellow beings under certain circumstances to that of the ocean fish who never realized there was such a thing as water, being continuously surrounded by it, until some unfriendly circumstance threw him on shore to his utter bewilderment. But we do not need to use this illus1 Presented before the Eighth Summer Conference of the New %dsnd ~ ~ ~of chemistry ~ ~ Teachers i ~ at t ~ ii d ~d College, Middlebury, Vermont, August 21, 1946.
tration metaphorically. We, too, live in an ocean, and at the bottom of it a t that. If our rocket enthusiasts ever succeed in transporting us to the moon, we will be in the same situation as the fish stranded on land, far from his familiar and essential ocean. The experience will be equally unpleasant, although we would undoube edly take more thought to protect ourselves from the change than does the fish. It is easy for us to think of the d&p sea fish as being under tremendous pressure. We can fairly feel the weight of all that water above him. We easily understand Dr. Beebe's diculties in constmeting his bathysphere to withstand pressures half a mile beneath the sea. But as soon as we try to transfer that experience to our own situation, we invent a mythical opposite of pressure and label it suction. This is clear evidence of the d i c u l t y we have in coniiincing ourselves that we live at the bottom of a very ponderable ocean and that an evacuated metal box crumples because it cannot support itself against the weight of the aerial ocean above it. We think of it as being "sucked in," and suction, like the Brobdmgnagian definition of falsehood is "the thing that is not." Of course, our ocean is diierent from the fish's in having no definite top. Being gaseous, it is very sensitive to pressure and decreases in density as we go upward, finally diminishing asymptotically to the almost perfect vacuum that rules outer space. Nature does not abhor a vacuum. Parallelmg Lincoln's remark about God and the common people, nature must love a vacuum because she made almost infinitely more of it than.of anything else. It is only because we live a t the bottom of a n ocean, without realizing it, that for us a vacuum is d i c u l t to produce and maintain. In spite of the indefinite surface and varying density of our ocean it is perfectly easy to find out the weight of it. Supposedly, everyone knows that atmospheric pressure is, roughly, 15 pounds to the square inch, but . I suppose relatively few people realize that this figure means just what it says. Above every square inch of the earth's surface there is about 15 pounds of air. We ~need b ~ to~ multiply ~ this figure by the number of ~ ~ only square inches on the earth's surface to find the total
406
AUGUST, 1847
weight of the atmosphere. The resulting figure is 6 X 1016tons- that is 6 quadrillion, or 6 thousand million million, tons. Air is therefore one of the world's most important raw materials. It is contmously mixed, constant in composition, universally accessible, needs no transportation medium, and so far nobody has found out how to tax it. Consequently we pay very little attention to it. Incidentally, an ordinary living room, say 15 X 20 X 8 feet contains about 170 lbs. of air. A large lecture hall may contain two or three tons of a&unless it is excessively warmed in one way or another. CONSTITUENTS OF THE AIR
Everybody knows the major constituents of the air and many of the minor ones. Remembering that air is neither an element nor a compound hut a mixture of elements and compounds, all of which can be separated from it fairly easily if necessary, let us consider the importance of some of these ingredients in industry and in daily living.. (1) Oxygen: This element is second in proportion in air, constituting about 21 per cent of it by volume and a trifle more by weight. It is, however, obviously the most significant constituent of air from our point of view since it supports combustion and life. The fact that i t is diluted with nearly four times its volume of nitrogen is of great importance. For most purposes the nitrogen is merely an inert diiuent, like water in certain beverages. We could live with an even lower concentration of oxygen; in fact, people in Boliva and in Tibet do live in air having only about half the oxygen concentration with which we are familiir. We could live withahigher proportionof oxygen. Pure oxygen has certain bad effects if breathed for too long but this is probably merely because, in the course of evolution, our bodily processes have been adjusted to the particular concentration available. The inescap able diiculty of living in an atmosphere containing a high proportion of oxygen would be the ease of starting a fire and the difficulty of putting fire out. All combustible materials catch fire easily and burn fiercely in high concentrations of oxygen, and in addition, such common metals as iron, zinc, tin, and aluminum hum furiously. Forests would certainly he destroyed under these circumstances due to fires started by lightning, and therefore forests could never have grown in such a world. Other vegetation could probably exist only in small patches, and with difiiculty a t that, because of the fertilizing value of slowly decaying material, most of which would burn up in a highly oxygenated atmosphere. Animal l i e depends on vegetable life; hence with too much oxygen we wouldn't he here. Marine life of all kinds would, however, get along better. The quantity of oxygen cpnsumed per year is so tremendous that it is by great odds our most used raw material, with the exception of water. I n breathing, the human race absorbs and uses about 3,000;000 tons of oxygen per day. Each of us uses about three pounds.. How much other forms of life may use would be much
407
more difficult to estimate and I have not attempted it. For every ton of coal burned, about 2.7 tons of oxygen is required, or about 13.5 tons of air. This amount of air must go through our furnaces Tor every ton of coat we shovel in. No wonder we are concerned about a good draft for our fires. For every gallon of gas our automobile engines bum, about 22 pounds of oxygen, or 110 pounds of air, must go through the carburetor, assuming perfect combustion. For every ton of iron produced in a blast furnace, about five tons of air must be blown through, making air the raw material used in the greatest tonnage by the iron industry. Assuming, as a very rough figure, that the total annual world consumption of all kinds of fuel is the equivalent of two billion tons of coal, we use for combustion over five billion tons of oxygen contained in 25 billion tons of air every year. Imagine the consternation of both industry and the householder if this material had to he mined, shipped, and paid for, and if its delivery could be interrupted by strikes, weather, and war. We frequently discuss the possibility of the exhaustion of oil deposits and of coal. How about the exhaustion of aerial oxygen? Only a very rough e 5 timate can be made as to how long our oxygen would last if there were no replenishment, hut assuming that we use five billion tons a year for combustion, that forest fires and the like consume another billion tons, that the human race uses a billion tons for the internal burning of food, and that the animal kingdom uses another billion tons, we have a total annual consumption of eight billion tons. At that rate the oxygen of the air would be completely used in about 150,000 years, although using the laat few per cent of it a t all would be very difficult. Fortunately, oxygen is continually being fed back into the air by vegetation, and the composition of the air is supposed not to have changed detectably in the century or so during which accurate analyses have been made. As a matter of fact, this is pure supposition. If none of the oxygen used from the air in a century were replaced, the proportion of oxygen in the air would decrease by only about 0.07 per cent of its value-that is, by 0.015 per cent out of a total of 21 per cent. Actual determinations of the oxygen content of the air, made by different analysts a t diierent places, differ by several times this figure, and there is no certain evidence that the proportion of oxygen in the air is being maintained. The solubility of oxygen in water is low; less than one volume of the gas dissolves in 100 volumes of water a t complete saturation a t ordinary temperatures and under normal atmospheric pressure. The aetual proportion of dissolved oxygen in natural waters is nearly always very much less than this. Yet it is on this small concentration of dissolved oxygen that fish depend. They will, of course, drown in deoxygenated water. Now while it is possible for cold-blooded creatures to get along with this low availability of oxygen, warm-blooded creatures cannot do so. Hence there are
408
no warm-blooded creatures which live by means of dissolved oxygen, and consequently t,he level of intelligence of fish is low. Intelligence seems to require an even and fairly high temperature. As mentioned before, if the atmosphere were pure oxygen, aquatic life might get along better. There mould be, on the average, five times the concentration of oxygen in the water that now exists. .Aquatic vegetation would get along all right, fish would be much livelier, and fire would still not be able to penetrate water; Even under these circumstances, however, the development of warm-bloodedness and of intelligence would probably be impossible for sea creatures, and the falsely seductive mermaid would still remain a myth. For all' the purposes mentioned, we use a i r directly. The proportion of oxygen separated from the air to be used in the pure state is insignificant. Dr. Langmuir's report on his recent visit among the Russians, however, gives rather clear evidence that such will not be the case indefinitely. Accordmg to his report, Russian scientists have developed a remarkably cheap process for separating oxygen from the air and expect to use the gas directly in the blast furnace and the Bessemer oonberter. They claim a Bixfold production from the blast furnace compared with that obtained by the use of air and Bessemer blows completed in one minute. For about half a century the America steel industry has played with the idea of using oxygen in this way but has always casually dismissed the notion as being hopelessly expensive. Has our industry missed a bet? (2) Nitrogen: This element constitutes about 78 per cent of the air by volume and slightly less by weight. Its indirect importance as a diluent has been referred to already. But nitrogen is necessary for life, as all proteins contain it, and life without proteins is not known to exist. It is an aloof element, however, capable of forming a large number of important compounds, but exceedingly reluctant to do so. With one isolated exception it does not occur in mine'rals. How, then, did living things 6nd the necessary nitrogen compounds to get started a t all? One vay of making oxygen and nitrogen combine, with the eventual formation of nitric acid, is to pass air t,hrough an electric arc, thus heating it to about 3000" C., and then cool the exit gases before the nitrogen has a chance to sneak out of its forced contract. Now lightning flashes are a k i d of electric arc which is almost instantaneously extinguished, thus permitting rapid cooling of any products formed by it. It is estimated that about 100 lightning flashes per second occur over t,he whole earth, representing four billion k i h watts of continuous power. Two million tons of nitric acid are thus produced from the air per day, or over seven hundred million tons per year. This amounts to 12 pounds per acre of the earth's surface. The acid is dissolved in raindrops and thus brought to the surface of the earth or to the ocean, thereupon reacting with minerals or sea water constituents to form nitrates, a form of combined nitrogen which plants can use. This is rob ably the primal source of nit,rogen forliving things.
JOURNAL OF CHEMICAL EDUCATION
In the course of time certain bacteria developed the ability to "fix" nitrogen; later certain plantet.lre legumes-developed hotels for these bacteria in the form of nodules on their roots. Here the bacteria live in apparent comfort, providmg the plant with the nitrogen compounds it needs in return for room and board. The only natural nitrate minerals-the isolated exception previously referred t e e x i s t in a single deposit in the desert regions of northern Chile. These are believed to be the result of the prevalent thunderstorms in the western outposts of the Andes. The resulting ,mineral nitrates were brought into the desert region by flash streams flowing down the mountainsides. Such water evaporates without ever reaching the sea, and the nitrates are left in solid form. A continuance of this action over a considerable geologic period seems to be the only tenable explanation of the Chilean nitrate deposits. Before the first world war, these deposits were the world's chief source of combined nitrogen for fertilizer and for assorted chemical purposes. The export tax supported the Chilean Government, and the country was otherwise tax-free as far as the federal government was concerned. A relatively small amount of nitrogen had been artificially fixed in this country by the cyauamide process and in Germany and Norway by the arc process. Only t,he cheap electrical power from hydroelectric plants using streams falliig down the precipitous headlands of the fjords in the latter country made this process economically feasible. During the war, the Germans, forced by the traditional mother of invention, ,learned how to force nitrogen and hydpogen to combine under the influence of n catalyst t,o produce cheap ammonia. After the war all industrially developed countries began using thk process, demand for Chilean nitrate, and its price. fell decidedly, and the Chilean Government became involved in difficulties in extracting. its taxes from its own people instead of from everyone else. For the Haber process, as the one just referred to is called, it is necessary to have a source of nitrogen freed from oxygen. One of the most important methods for doing this is the fractionation of liquid air. Thus, for the first time, liquid air ceased to be a mere laboratory curiosity and became an industrial product in large topnage. There is nothing which should be confusing to t,he mind in regard to liquid air. Any gas will liquefy if cooled sufficiently. If the temperate and torrid zones of the eart,h were at a temperature above 100°C.one mild enough compared with that with which some of us have been t,heologically threatened411 water mould be gaseous and part of the atmosphere. If then, some intrepid explorer returned from the polar regions with the yarn that at the frigid temperatures of 25 to 50°C. which prevailed there in the winter, water became liquid and descended from the air in drops and formed pbols on t,heground, it would be some time beforc . he would be able to overcome the suspicion t'hat he was a member of the Xunrhausen clan. If the temperature
AUGUST, 1947
of our planet were 200' or more helow zero Centigradea condition certainly obtaining on the outer planets of our system-the whole atmosphere would be liquid, and would cover the earth to a depth of 42 inches if evenly spread out. It wouldn't be, of course, but x~ouldform a deeper layer on top of the solid ice of the oceans. As i t is, there are two practicable means of persuadmg highly compressed air to cool itself off sufficiently so that part of it liquefies. If the liquid is allowed to boil, the nitrogen, which boils at a lower temperature than the oxygen (-195'C. as against - 183'C. for oxygen), tends to boil off h t , just as the alcohol in a car radiator tends to boil off in preference to the water. By careful fractionation-the same process that is used at higher temperatures by the petroleum and alcohol industries-the two gases can be cleanly separated. Quite pure nitrogen is thus obtained cheaply, and as hydrogen can also be prepared cheaply, the final product, ammonia, can compete very successfully in the xvorld market. In 1936 the world production capacity of ammonia by this process was 3,700,000 tons per year. To produce this quantity would require mining the air for 3,000,000 tons of nitrogen. .During the war these quantities were probably i n o r e a d by fifty t.0 one hundred per cent. By further use of air, ammonia call be catalytically burned and converted into nitric acid. Practically allof this product is now made in this way, about 200,000, tons of the acid being produced in the United States in n normal year, and perhaps twice t,his amount during the last few years. Thus the major constituent of our atmosphere has a t last been put to work. The quantity available is so enormous that it is useless t,o calculate how long the supply will last. Most of the nitrogen combined gets free and ultimately rejoins the atmosphere anyway: (3) Water: Water is the third constituent of our atll~ospherein either volume Or weight Per cent. volume it constitutes, roughly, from 0.2 to$ per cent of t'he air, depending On temperature and, humidity. Sinre water is easily available as a liquid, no commercial use is made of that contained in the atmosphere. As s matter of fact, it is often a nuisance. It cools down the blast furnace and some plants now remove part of the water from the entering air by refrigeration. Air conditioning systems require a device for removing part of the water content of the air at times of high humidity. Nevertheless, we are absolutely dependent upon the water-carrying power of our atmosphere. ~t is estimat,ed that about 70,000 cubic miles of water evaporate from the ocean annuauy and fall as rain eventually. The annual rainfall, therefore, has a weight of about 3 X 1014tons and as a minimum figure, ljecause much mat,er evaporates from land and fresh water sources. Thus the atmosphere carries each year about one-tenth qf its own weight of water. About 20,000 cubic miles of this rainfall occur over the land, and it is this trernendous transport of watter by the atmosphere that
409
makes terrestrial life possible a t all. In addition, it has important geological effects. Every year two and three-quarter billion tons of dissolved material is carried into the oceans by rivers, a process which, in the course of geologic time, has made the ocean a sort of reservoir of the entire periodic system. Still greater quantities of suspended materials are delivered by rivers. The estimate for the Mississippi alone is 307 million tons of silt per year. (4) The inert gases: Although i t had been known for over a century that nitrogen obtained from the air differed slightly from nitrogen prepared by chemical means and always left a slight residue which would not combine in any chemical process, it was not until the eighteen nineties that the cause of this difference was made clear by Rayleigh and Ramsay in Eugland. They found that nitrogen from the air was contaminated wit,h about one per cent of a previously unknown gaseous element which they named argon. This gas is thus the fourth constituent of t,he air'in abundance. Ramsay later found that the argon which he had obtained was, in turn, not pure, but contained traces of helium, neon xenon, and kpton-all gases very similar to argon. These gases are the delight of the chemist,ry student, because when onecomes to discuss their chemical properties, ordinarily the most important and complicated section of one's remarks about an element, the only thing to be said is, "chemical propertieenone." They are utterly inert, form no compounds, and do not even form the cust~omarymolecules by pairing their own atoms. They are often called the "noble gases," a term apparent,ly based on the ancient notion that it is noble to dano rn.ork. Nevertheless, changing econo& conditions have forced nobles of all kinds to untraditional labor, and these gases have not completely escaped. Argon, obtained by fractionation of liquid air dllring the preparation of is in electric light bulbs, especially those of high wattage; 'rbe argon-filled bdlb gives greater efficiency in converting electriql energy into light than the nitrogen-filledbulb. ., Neon, also obtained by fractionating liquid air! has gained a flashy career in commerce. Fortunat,ely,.the neon tube is highly evacuated, containing only a minute amount of the gas, as the element is present in air only to the extent of 15 millionths of a per cent. and is therefore expensive' Krypton and xenon occur in such utterly minute traces that only some extraordinarily important purpose for which they were uniquely suited would justify their extraction. The same could be said for helium if air were its only source. Fortunately, this element can be obtained quite cheaply from certain gas wells in the Texas region. It is used for inflating balloons, being second only to hydrogen in lifting power, and as a diluent for oxygen in a sort of artificial air for men working under very high atmospheric pressure. The most recent use for helium emphasizes again the weight of air. The air transport
JOURNAL OF CHEMICAL EDUCATION
companies have found that by inflating the great tires on the landing gear of the largest transports with helium instead of air, they can save 180 pounds of weight per plane, thus adding this amount to the pay load. (5) Carbon dioxide: The proportion of this gas in the air is quite small, only about 0.03 per cent,. In spite of. purposeful combustion and heedless conflagration, air is so well stirred that the carbondioxide content is virtually constant everywhere. Carbon dioxide can he obtained so easily and cheaply from flue gases, the fermentation processes, and the calcining of lime that its presence in the air is of no direct industrial significance. Nevertheless, it is from this small percentage of carbon dioxide in the air that a11 our food and fuel come. Only the green-leaved plants can use solar energy and atmospheric carbon dioxide to produce the multitude of complex organic compounds of which they are made and -- some of which arc the ultimate source of food for ail animal life. Presumably this type of synthesis will eventually become a laboratory accomplishment; it is not as yet. So to date, life is completely dependent on this constituent of the air also. It is a well-worn statement that when using Fuel for heat and light we are releasing solar energy conveniently canned for us during the carboniferous period. It is equally true td my that we are using carbon and carhon compounds produced in that ancient age from the atmospheric carbon dioxide of the time. (6) Local variables: Other gases, the presence of which is undetectable in the general mass of the atmosphere, are occasionally locally important. When one walks out on a cold winter's morning one's nose is often assailed by the delectable flavor of sulfur dioxide from, I trust, a naighbor's chimney. This gas, being eventmlly converted into sulfuric acid, is responsible for a great deal of the disintegration of paint, fabrics, and metals whichydagues our pockktbo?ks. It comes from the presence in bituminous coal of a notable percentage of sulfur and makes this fuel, all thimgs mnsidered, the most expensive means of warming- the houses of a commumiti Volcanos also deliver large volumes of sulfur dioxide to the atmosphere, but there are other reasons for not living in their neighborhood. Sulfur springs in certain regions provide the unhealthful flavor of hydrogen sulfide to air in their vicinity. On the very local contributions of laboratories of chemistry and biology I will not comment. The atmosphere itself is not to be blamed for the presence of any of the ingredients mentioned in this section. Beside the services rendered by individual constituents of the air, the atmosphere as a whole has very important functions. Air in motion, as during a hurricane, ordinary storm, or even comfortablebreeze, has enormous energy and momentum. A cubic mile of air is a rather small amount from the point of view of weather, but it weighs over five million tons and is very
persuasive when going somewhere in a hurry. That we are surprised a t the effects of cyclones and humcanes is merely further evidence that we fail to realie that air is honest matter and has weight. I do not know that anyone has tried to estimate the average continuous wind power. a~ailableon the earth. It is certainly many times greater than any possible power requirements of the whole human race. Sailmg craft and windmills used to tap an insignificant fraction of this power before steam and electricity rose in their might.' The first modern attempt at effective use of wind power, as far as I know, was by the Central Vermont Electric Company which five years ago erected a large steel tower on one of the northern Taconics and equipped it with a self-feathering air wheel having four stainless steel blades weighing five tons each. This wheel, driven by the prevailing westerlies of the region, drove, in turn, a generator feeding power into the company's network. Operation was successful until a hurricane destroyed the wheel. Plans are under way for the construction of others, and the time may come when the Taconic range will seem from afar to support a picket fence bearing pinwheels. At any rate, a considered attempt is being made to put wind power to work. ATMOSPHERIC PROTECTION
"Transparent as air" is a casual phrase. Fortunately however, air isfullytransparentonlytosu5ciently long-wave radiation. In the ultraviolet region its transparency is mercifully limited. This again is an absolute requirement for life. .Enough ultraviolet radiation sneaks through to give one a painful sunburn on a hot summer's day and to assist in the formation of some of the essential vitamins, but no living things and very few organic compounds could long resist the undiminished energy of sunlight in these wave lengths. This is another hazard our lunar voyager would have to take into account, along with a midday temperature above that of boiling water. The atfiosphere also protects us from meteors, of which more than twenty million enter it daily a t a velocity of some 30 miles per second. Even the thin air a t a height of 70 or SO miles produces enough friction to heat their surfaces to incandesc&ce, and most of them disintegrate to dust before reaching the surface of the earth. If it were not for our aerial shield all of these particles would strike the earth, and the smallest of them would be more deadly than a rifle bullet. We would be a t continual warfare with outer space. Again, let the lunar traveler beware. No friendly atmosphere will protect him on our naked satellite. The atmosphere helped Marconi most unpredictably in his invention or discovery of the wireless transmission of electrical signals. All electromagnetic radiation travels in straight lines, and thus it was clear that impulses from a sending antenna could, owing to the curvature of the earth, be received only as far as a bright light a t the altitude of the antenna could be seen.
AUGUST. 1947
For short radio waves this is strictly true and is the most important limiting factor to the distance over which radar and frequency modulation can be used. Yet Marconi was able to send messages from the British Isles to Newfoundland, and radio stations have been "picked up" nearly half way round the world. This is possible, as all radio discussions tell us, because a t a height of 50 to 80 miles there. are regions of ionization &the rarefied atmosphere. These act like a sort of chbination mirror and lens toward long wave lengths of radiation, turning the waves back toward the earth. From the earth they may be in turn reflected and then again returned by the ionized upper atmosphere, although these repeated reflections diminish their intensity sharply. The effect of these Kennelly-Heaviside layers, as the ionized regions are called, is not nnlike the effect of air layers of varying density in producing a mirage. At any rate we can say that it was our atmosphere that made the first steps in radio possible.
THE FISH'S O C m Now let us turn our attention'from our ocean to the fish's ocean. His ocean is not so voluminous as ours, but there are over 300,000,000 cubic miles of it, weighing about 1.57 X 1018tons. There is, as has previously been pointed out, a considerable trade between the two oceans, the aqueous one contributing about 70,000 cubic miles of its substance to the aerial one every year and receiving i t back again bearing a high tonnage of dissolved and suspended minerals. The cubic mile is one of those handy units of volume which we can use glibly for very large quantities without realizing how large a quantity it is itself. Converting it into terms of one of the larger units used industrially, the slide rnle shows that it is 26.4 billion barrels. This is almost precisely the total world production of petroleum from the dawn of the industry through the year 1940. If we further divert ourselves by cgnverting the volume of the ocean into laboratory terms, i t is easy to show it to be about 1.25 X lo2' ml.-that is, there are almost exactly twice as many milliliters of water in all the oceans as there are molecules in a mol. As far as I know only one poet has caught a vision of this most essential feature of the ocean. Byron's "Roll on thou dark and deep blue oceau, roll" is typical of the general poetic attitude. But A. E. Houseman, writing to his brother on the subject of the sea, called his attention to the fact that one of its outstanding attributes had never been celebrated in ver-whereupon he proceeded to do s o i n a number of stanzas, some of' which I quote: 0billows, hounding far How wet, how wet ye are. When tirat my gaze ye met I said, "Those waves are wet." Thy zoctnass 0 thousea Is wonderful to me.
Xo object I have met Is more profoundly wet. It agitates my heart To think how wet thouart.
It is this excessive wetness, so keenly felt by the poet, that makes the recovery of mineral assets from the There is so much water! But the total quantities of ions of even the rare elements dissolved in the oceau is astounding. ITS CONTENTS
All told there are about 4,800,000 cubic miles of salts in solution in the sea. This is enough solid salt to cover the territory of the United States 1.6 miles deep. The total weight is about 4.9 X 1016 tons. The larger proportion of this material, is, of course, sodium chloride, present in the ocean to a weight per cent of nearly 3.5, and therefore economically recoverable. However, most of the large tonnage of salt used in industry and commerce comes only indirectly from the sea, being derived from salt beds created by solar evaporation o? large arms of the ocean cut off by geologic processes. So it is only the recovery of materials present ip higher dilution that is industrially interesting, but even of these the total tonnage available is so large as to seem almost absurd. 1.7 X 10'5 tons of magnesium, 5.5 X 10'' tons of calcium, 5 X 10 l 4tons of potassium, 1 X 10" tons of sulfur, and 8.7 X 1013tons of bromine are dissolved in one form or another in the sea. Furthermore, the annual additions of these elements to the ocean are far greater than any conceivable industrial consumption., .. It is only mthin relatively recent years that the ocean has been used as a direct source of any of these elements. It takes over ten thousand tons of sea water to contain one ton of bromine, yet, as we all know, ingenious chemical processes and clever location,of plant have made it possible to obtain this element economically from sea water in quantities large . enough - to satisfy the total d e mand. Also a matter of common knowledge is the fact that magnesium has been recovered in large tonnage from sea water as a war project and that this process produced the metal more cheaply than any based on the use of. highly concentrated and extensive ore minerals. None of the other elements has been obtained commercially directly from the ocean, although for a long time the principal source of iodine was kelp, a sea weed which in its metabolism concentrated iodine in .its tissues to some extent. There is available in the ocean, however, on the order of 3 X 10'O tons of iodine as iodate, if the lowest reports be accepted. It would be necessary to process nearly 50 million tons of water to obtain one ton of iodine with perfect efficiency. Probably no state with a seacoast has avoided the attentions of gold-from-sea-water promoters a t one time or another. Equipped with a boat or barge, some inexpensive but impressive electrical equipment, some
JOURNAL OF CHEMICAL EDUCATION
gold ingdts large enongh to excite admiration without requiring t,oo heavy a capital inrestment as visible equipment,,and a diver not exposed to t,he public gaze, credulous "investors" were rednced to t,he proletariat in considerable numbers. The actual proportion of gold in the ocean has been reported in absurdly variable figures. In 1927 Haber published the results of careful investigations, showing the figure to. be much lower t,han had previbusly been supposedbut to be widely variable in fact. The average of 13 reported determinations in areas where the greatest gold content was found is 5.4 milligrams per metric ton. At this rate the total gold content of the ocean would be about e r this, eight billion tons. It is undoubtedly l o ~ ~ than but certainly of the order of a billion tons, and the silver content is several times as great,. If all t.he radioactivity of ocean ~ ~ a t ise rdue to radium, there must be between 2000 and 20,000 tons of that element in the ocean. Of course, t,he entire periodic system is there. To take another example from among the rarer elements, about 2 X loz3tons of rnbidinm is present in sea water -64,000 tons to each cubic mile. Certain sea creatures contain notable amounts of vanadium, manganese, copper, cobalt, nickel, and cadmium, all of which must be derived from sea water. When the tempting quantit,ies of some of the el& ments present in the sea beguile anyone to consider. practical recovery, he can only groan ~viththe poet It agitates my heart To think how we1 thou u t !
Yet the rapid depletion of concentrat'ed ore deposits, which are almost always rare and insignificantly small from a geological point of vie*., may force consideration of the use of dilute but practically limkless sources instead. Perhaps, l i e physical chemistry, it& the fate of industry to proceed from the reasonably concentrated to the infinitely dilute. While it would clearly be hopelessly uneconomical to push around and process the vast hulk of sea water which would be required to ohtain commercial quantities of the more dilute constituents-if the aim were to obtain-these a l o n e i t is interest.ing to note that significant quantities of them might be obtained as by-products when the water was being processed for such an element as magnesium. About a million tons of sea ~ a t ' e must r he treated to produce 1000 tons of magnesium. If, during the trip of the water through the plant, it conld be run through units designed to extract other elements, about 50'tons of bromine, 36 pounds of iodine (as a minimum estimate), 25 pounds of silver and 10 pounds of gold might be recovered. Research on methods of recovery of ions from excessively dilute solntion might eventually pay dividends and a t least begin to put t,he ocean to work as a source of mat,erials.
