Symposium on Chemistry of the Sea A SHORT HISTORY OF OCEANOGRAPHY WITH EMPHASIS ON THE ROLE PLAYED BY CHEMISTRY' THOMAS G. THOMPSON Department of Oceanography, University of Washington, Seattle
THE
seas and oceans of the world have played a major role in the history of human endeavor and achievement. Contemplation of the wonders and mysteries of the sea have intrigued the thoughtful mind from the earliest times. Some of the classics of literature of many lands are sagas of the seas. Three general objectives had to he realized before the full exploitation of the seas, either economically or scientilically, was possible. These three objectives were: (1) the construction of suitable ships to permit safe transportation, (2) the invention of navigational aids and equipment which would enable a mariner to chart and maintain his course and t o ascertain his location at sea, and (3) the exploring and charting of the oceans and seas of the world. The development of each one of these objectives stretched over many centuries, and the evolution of each reflected the result of knowledge gained a t sea. Some of this knowledge became an essential part of the science of oceanography. The development of different types and characteristics of ships in various regions of the world and the general evolution of ship design through the ages demonstrate how some of this knowledge was applied. The acquisition and use of astronomical information and data, the invention of the compass, the sextant, and the chronometer were fundamental for navigation and the determination of exact location at sea. The extension of geographic knowledge of the western world began with the voyages of the ancient peoples who inhabited the shores of the eastern Mediterranean Sea and culminated in the voyages of the great discoverers, from Christopher Columbus to Captain James Cook. Mention should also be made of the important navigational and oceanographic knowledge possessed by the peoples of Polynesia. Only recently has the western world come to appreciate the profound knowledge these people possessed of the characteristics of the sea, for without compass, they made voyages over the vast areas of the Pacific. The
' Presented as part of the Symposium on Chemistry of the Sea before the Division of Chemical Education a t the 131st Meeting of the American Chemical Society, Miami, April, 1957. Contribution No. 215 of the Department of Oceanography, University of Washington.
famous voyage of the Maoris of some 2500 miles to New Zealand in A.D. 1350, and their prior voyages between small islands hundreds of miles apart, dvarf in some respects the voyages of Columbus nearly 150 . years later. The contribution of an oceanographer to the science of the sea is invariahlv closelv related t o his trainine and experience in one of the basic sciences in which he is also more or less of a specialist. He will often describe his activities in oceanography in relation to his basic specialty, such as physical oceanography, chemical oceanography, biological oceanography or marine geology. I n presenting this paper, emphasis will be given largely t o the role played by chemistry in the general development of oceanography. Chemists concerned with the study of the seas are interested in the nature and concentration of the many constituents comprising sea water; the composition of the sea floor; and the numerous chemical reactions taking place within the sea, on the sea floor, and at the surface of the ocean as a result of contact with the atmosphere. Among a few of the other problems that engage their interest are: (1) the effect of changes in temperature, pressure, and concentration of dissolved salts upon the physical properties of sea water; (2) the study of the mechanisms that enable marine plants and animals to select and concentrate within their structure elements that exist only in minute traces in sea water; (3) investigations of the cycles of the different elements of constituent in the general economy of the sea; (4) the study of changes that may have taken place in the oceans or the sea floor during geologic time; (5) the recovery of chemicals and products of economic importance from the waters of the ocean and from marine organisms; (6) the effects of pollution of harbors, estuaries, and even the oceans themselves; and (7) the investigation of the corrosion of metals and other materials when exposed to marine conditions. I n order to comprehend the extent and nature of the oceans, a few elementary facts may he mentioned: 70.8% of the area of the planet is covered by the waters of the seas and oceans, 80.9% of the southern hemisphere is salt water, and 60.7y0 of the northern hemisphere is salt water. The oceans, including the u
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seas, have an average depth of 2.3 miles. Should all the areas now land be moved into the ocean depths, and should the ocean depth be made uniform over the planet, there would be nearly one and one-half miles of water over the entire face of the earth, and if water were absolutely noncompressihle, sea level would be about 90 feet higher than it is. If all the salts in solution were removed and placed into one pile, a mass approximating the size of the African continent would result.
ical industry that had its origin in the sea, namely the preparation of dibromoindigo. This industry appears to have had its origin in ancient Crete, but it was later highly developed by the Phoenicians. Dibromoindigo is a dye imparting a magnificent purple color to rloth and was known as the purple of Tyre, or Tyrian purple. It became a famous and important article of Phoenicians' commerce. The dye was extracted from a small gastropod, and an enormous quantity of these organisms was required to yield a small amount of dye.
SALT IN THE SEA
ROBERT BOYLE
The saltiness of the sea aroused the curiosity of the ancient philosophers. They attributed the saltiness t o the action of the sun; in other words, the sun produced salt. This conclusion seemed logical because sea water, when placed in a shallow pan and exposed for some time to the sun, would disappear and crystals of salt would form. From this they reasoned that the water below the surface of the sea was composed of fresh water. Salt, or sodium chloride, was a highly prized commodity of the ancient world. The height of hospitality was to offer a visitor or wayfarer salt. On festive occasions, the persons of highest rank always sat nearest t o the vessel or dish containing the salt. Many superstitions centered around the use and handling of salt. Salt was often used as a medium of exchange. The soldiers of the Roman Legion were often paid in salt, hence our word salary. This ancient custom of remuneration with salt existed to our own times, as the Italians discovered when they conquered Ethiopia. I n the more remote regions of this country, the Italians attempted to pay the native laborers with Italian lira. The money WAS refused. However, workers were readily secured when offered discs made of sodium chloride. Salt is absolutely essential for all animal life. It is also one of the five basic raw materials of our modern civilization. These five materials are air, water, coal or oil, sulfur, and salt. ' Each one of these materials is involved in everything produced or manufactured. The production of sodium chloride from the sea is the oldest of all chemical industries, and ancient people living by the sea engaged in its recovery. This was a relatively simple process for people living in arid or semi-arid regions, as the sea water was conducted into basins and allowed to evaporate. In other regions, evaporation was not possible. Julius Caesar described the method used by the ancient people of Britain, who built fires of charcoal and then poured the sea water, or brine, on the fire and recovered the small particles of salt formed on the quenched charcoal. Names of many localities in England are an indication of the antiquity of the salt industry, as the suffix wich (as in Norwich, Sandwich, Harwich) designated a place where salt could be dug or bay salt obtained. A salt forest was one that provided wood for making the charcoal. Suflixes equivalent to wich are found in all the languages of northern Europe. From prehistoric times the Scandinavians prepared salt by permitting the sea water to freeze and removing the ice a s it formed. The resulting brine was then thrown on charcoal fires and the salt crystals were removed. I t might be of interest to note another ancient chem-
The father of modern chemical oceanography may be said to be Robert B o y l e t h e same Boyle known to students of science for the law which states that the volume of a gas varies inversely as the preesure, temperature remaining constant. About 1670, Boyle published a remarkable treatise entitled "Cbservations and Experiments on the Saltness of the Sea." Boyle conducted a number of experiments on sea water and gathered, through interviews, much information from mariners and divers. He devised the first chemical test for ealt water, adding silver nitrate to a sample of water. A heavy white precipitate was produced. He also took samples of London pump waters and water collected from English rivers and lakes. None of these waters gave a dense white precipitate, but all produced a faint white cloud, indicating a trace of salt. Boyle concluded that all fresh waters contained a small quantity of salt, that the salt of the sea resulted from leachings from the land, and that the acrumulation of these leachings in the sea produced saltiness. Boyle believed he could measure the concentration of the salt in a given volume of sea water by allowing the water to evaporate in a weighed dish and weighing the dish again after the water had been expelled. This seemed like a simple and logical method, yet with numerous repetitions, using the same mmple of sea water, he could seldom get results that agreed. He correctly concluded that this method was undesirable as a measure of the concentration of salts in the water. Boyle made many specific gravity determinations of sea water, and from these he concluded that it was most desirable to express saltiness by this means. He knew that the saltiness varied with geographic location, as his maritime friends had told him that their vessels would float a t different heights in different regions of the world. These friends had also told him of their method for cooling their wines by lowering the wine bottles some distance below the surface, and one told of how the cork had even been forced into the bottle when it had been lowered to a considerable depth. As a result of this information, Boyle and his assistant devised a method for measuring the pressure of water exerted at different depths. Boyle also collected considerable information on the temperature of the sea a t various depths and had divers collect samples of water for hi. From these studies he concluded that the temperature of the water decreased with depth and the saltiness increased. However, he noted that the salt content of sea water a t several depths off the British Isles was relatively uniform. Boyle also postulated that the floors of the oceans were very irregular, that the tranquility of the seas increased with depth, that the effect of tidal phenomena on abyssal
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waters was questionable, and that occasionally in swiftly moving waters, in narrow channels, the direction of the surface current would be the reverse of that of the current near the bottom of the channel. Boyle'e assistant was Robert Hooke, who later became a famous experimental philosopher himself and is known to students of science for the law bearing his name, namely, that in the small strains on elastic bodies the stress is proportional to the strain. Hooke devised apparatus for sampling water from great depths which in principle is the same as used today, and he invented several pieces of equipment for measuring depth and for securing bottom samples. OBSERVATIONS IN THE EIGHTEENTH AND NINETEENTH CENTURIES
About a century after Boyle, Benjamin Franklin paid considerable attention to oceanography and, unlike Boyle, carried out numerous experiments while a t sea. Franklin, from information obtained from New England whalers, called attention t o the Gulf Stream, the warmth of its waters, the direction of flow, and he also plotted the current. He demonstrated that the thermometer could be employed as a useful navigational instrument, theorized considerably on the construction of the hulls of vessels, size and number of sails a vessel should carry, performed experiments on the use of oil as a means for quieting the seas, discovered one of the basic laws of hydrodynamics by noting that a vessel moved easier in deep water than in shallow water, invented the sea anchor,%correctly explained the cause of phosphorescence in the sea, and advocated the propulsion of vessels by pumping water from the stern of the vessel. Franklin disagreed with Boyle as to the origin of the saltiness of the sea; he maintained that the seas had always been salty. The famous voyage of the Beagle, the laying of the Atlantic cable, and the classical work of Mathew Foutaine Maury, one of the outstanding American scientists of the nineteenth century, did much to intensify the interest of the scientific world in the study of the oceans and seas. The interest of the British scientists led to one of the greatest scientific expeditions of all time, the Challenger expedition. The results of this expedition, physical, chemical, biological, and geological, are recorded in some twenty large volumes. The immediate interest of this expedition to chemists is the report of the Scottish chemist, W. Dittmar of the University of Edinburgh. Dittmar made extensive analyses of 77 samples of sea water collected by the Challenger from various depths of all oceans. Like Boyle, he pointed out the impossibility of ascertaining the total weight of salt by evaporating the water and weighing the residues. Dittmar made an exhaustive study of the work that had been done on the chemistry of the sea, listing all the elements that had been found by previous investigators in sea water, marine organisms, and boiler scales of vessels. It was his opinion, as the reeult of this review, that probably no element is entirely absent from sea water. Because of the limited volumes of the samples supplied him, he confirmed his investigations Tho method of using the see. anchor in strong head winds known to the Maoris centuries before Franklin, according to statement of Elsdan Beat in his book "The Maori as He Was." warr
to the major constituents of sea water. He demonstrated that, regardless of depth or geographical location, the ratio of any one of the major constituents in respect to the others was a constant. It may he postulated that sea water is of constant composition as far as the major constituents of sea water are concerned and that the nature of the water variec only as to the degree of the dilution. Knowing the consideration of any one of the substances a t a given dilution, the concentration of all the others may he calculated. Furthermore, the physical properties of sea water are a function of concentration, temperature, and pressure. Knowing the chlorinity or salinity, the modern oceanographer, by reference t o tables, can ascertain the physical condition of a particular water at different temperatures and pressures. Any changes in the concentration of the major constituents of sea water of a given chlorinity would generally occur in quantities measurable only by a fraction of a milligram. Because of the large amount of the major constituent already present, an analytical method with a precision of about 0.01% to 0.001% would be required to measure this minute change. However, with the minor and trace constituents, a change of the magnitude mentioned can be ascertained with ease, because the change is relatively large in respect to the mass normally present. In Table 1 are given the concentrations of the various constituents of sea water calculated as grams, milligrams, or micrograms of constituents per kilogram of sea water, and as gram atoms or milligram atoms per kilogram. The third and fourth columns of t,he table give factors which, when multiplied by the chlorinity of any sample of sea water, wid give the concentration of any particular constituent as grams per kilo of water, if the factor in the third column is used; and as gram atoms if the factor in the fourth column is employed. SALINITY, CHLORINITY, AND CHLOROSITY
Just before the turn of the century, scientists from countries bordering on the North Sea, who were interested in various phases of oceanography, met in Stockholm. From this meeting there evolved an organination known as the Conseil Permanent International pour L'Exploration de la Mer. The Council agreed early upon a system of standardization for expressing the concentration of sea water. Boyle had devised a test for measuring saltiness by adding silver nitrate to samples of sea water, which in reality tested for the halides present. This method of measuring the total halides, having been modernized by Mohr and later by Volhardt, can be accompli.rhed with ease and with marked precision and accuracy. Accordingly, the term chlori7iity mas invented and defined as a measure of the total halides, calculated as chlorides, in a kilogram of sea water. However, some scientists, particularly the biologists, insisted that it was essential to know the concentration of total salts. Chemists since Boyle had pointed out the difficulties involved in such a determination because of the multiplicity of hydrates that may he formed and the chemical reactions that take place when water is evaporated. A means of indicating the quantities of total salt, termed salinity, was finally agreed upon. The salinity was JOURNAL OF CHEMICAL EDUCATION
defined as the concentration of salts present in a kilogram of sea water when all the halides had been converted to chlorides, and carbonates and bicarbonates converted to oxides, all organic matter completely destroyed, and the entire mass heated to a temperature of 450% for seventv-two hours in order t o obtain constant weight. With such a definition, the salinity was directly related to the chlorinity. Upon the recommendations of the International Union of Geodesv and Geonhvsics. the term "chlorinity" was redefined in 1939 in reference to a given weight of ultra pure silver, making the standard water independent of changes in atomic weights. If the chlorinity is multiplied by the specific gravity of the sea water a t 20°C., the value obtained is known as the chlorosity of the water and is designated by the symbol Cl.. By multiplying the chlorosity by the ratio factors shown in Table 1, the concentration of the several constituents of sea water may be expressed as grams or gram atoms per liter of water a t 20°C. The Hydrogrnphical Laboratories of Copenhagen are charged with the preparation and dispensing of the standard water to all oceanographers throughout the world for the standardization of their respective solutions. This leads to a very uniform world-wide system of reporting fundamental data and makes all results readily comparable. During both World Wars, especially World War 11, it was impossible to secure the Copenhagen water. Each group of the warring nationals prepared their own standards, based on whatever Copenhagen water was available. However, TABLE 1 Concentration of Constituents in a Kilogram of Sea Water, 19.00% CI
Grams
Gram atoms or moles
G~aml
Gram atom1
Cl%o
CL%O
Maior Constituents (measurable a9 rrams) Chloride, CI18.980 ' 0.5353 0.9989' Sodium, Na+ 10.560 0.459 0.5556 Magnesium, Mg++ 1.273 0.0523 0.0670 Sulfate, SO4-2.649 0.0276 0.1394 Calcium, Cat+ 0.4104 0.01026 0.0216 Potassium, K t 0.3800 0 . 00097 0.0200
0.02817 0.0241 0.00275 0.00145 0.00054 0.00051
Minor Constituents (measurable as millimamsl Milligmm Milligram atoms Carbon (existing as HCOsor CO8--) 28.00 2.33 Bromide, Bi65.9 0 .824 Strontium, Srt+ 8.06 0.092 Boron (existine ss H.BO.l 0.424 4.58 Silicon ieristini as silica&) 0.01-4.5 Fluorin; . 1.4 Nitrogen (existing as nitrate) 0.01-0.80 Aluminum, Al+" 0.5 Rubidium, Rb+ 0.2 Lithium, Li+ 0.1 Phosphorus (existing as phosphate) 0.001-0.1 Trace Elemats (measu~ablein quantities from 60 to I mieroqmm) Barium, iodine, arsenio, iron, manganese, copper, zinc, lead, selenium, csesium, uranium. Trace Elaents (measurable in quantities less than 1 miwoq~am) Molybdenum, thorium, cerium, silver, vanadium, lanthanum, yttrium, nickel, scandium, cobalt. Cadmium, mercury, gold, tin, chromium, radium.
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as soon as hostilities ceased and communication was again possible, the various standards were checked to ascertain any necessary corrections that should be made. LIFE IN THE SEA
In the life cycle of terrestrial organisms, terrestrial plants are dependent upon a supply of fresh water, the carbon dioxide in the atmosphere, solar energy, and the nutrient material in the soil. This nutrient material consists of phosphates, nitrates, ammonia, potassium, silicates, calcium, sulfates, and numerous trace elements. Terrestrial animals, in order to exist, feed upon this vegetation, require water, and often prey on other animals. The breath of life is provided by the oxygen of the atmosphere. Plants and animals die, and in their decay the soil is enriched to provide nutrients for plants that are yet to be, which nil1 supply food for animals yet to be born. In furthering this life process, chemistry has played a most important role by increasing the productivity of the land. Biology has likewise done much to make possible better plants and animals. The sea is like the land. Vast expanses of ocean water contain a great variety of plants, many of them microscopic in nature which are suspended in the water and referred to as phytoplankton. The shallow portions of the sea floor also support an abundant marine vegetation. Animals of the sea graze upon the phytoplankton. Many of these animals are likewise microscopic and some are larval forms of large animals. These rather passively floating organisms are known collectively as zooplankton. Larger animals feed upon the smaller ones. Like the terrestrial plants, vegetation of the sea is dependent for growth on solar energy and so marine vegetation exists only to the depths at which sunlight will penetrate. The carbon dioxide, instead of being utilized from the atmosphere, is available in solution in the waters. All the nutrient chemicals required for growth, instead of being in the soil, are in solution. As the result of photosynthesis, the sea plant9 liberate oxygen which dissolves in water. The animals of the sea, with the exception of the marine mammals, depend upon dissolved oxygen. The marine organisms die, sink, and in the process of decay the bottom waters are enriched with nutrients. In various sections of the oceans, and particularly along some coastal areas, these abyssal waters, high in the concentration of nutrients, are upwelled and enrich the waters near to the surface, providing a fertile region in which plants may grow. Little has been done chemically to increase the productivity of the sea. However, important biological investigations have led to the writing of numerous international treaties. The purpose of these treaties has been to conserve fish and marine mammals of economic importance by regulating the numbers captured and methods of capture, or limiting the areas of operation. RESERVOIR OF R A W MATERIALS
The oceans and seas are vast reservoirs of raw materials. Future generations will depend far more than we do on the plants and animals of the sea as a source of food. The so-called seaweeds, while containing car-
bohydrates and proteins in concent.rations less than terrestrial plants, are rich in many vitamins and all of the trace elements that appear to be important to nutrition. Great quantities of seaweed are consumed in the Orient as part of the normal diet, but people of the western world spurn this type of food. B y reference to Table 1, it will be observed that bromine and magnesium ions exist in sea water in concent,rations very much less than the chloride or sodium ions. Within the past quarter of a cent,ury economical processes have been developed for the recovery of bromine and magnesium from sea water. These processes are spect.acular from the viewpoint of the vast quantities of raw mat,erial t,hat must he handled and the unique application of simple chemical and engineering principles by the chemical engineer. At the University of Washington, Dr. R. W. Moulton of the Chemical Engineering Department is investigating the possible recovery of borates from sea water, from which boranes, a fuel for jet engines, may he produced. Throughout the history of science there are many illustrations of recorded observations or discoveries, which for a time attracted much attention. Then, for reasons sometimes difficult to understand, these are neglected and forgotten only to he revived again and again after varying periods of time. The hist,ory of the distillation of sea water as a means for obtaining fresh water is a beautiful illustration of this strange phenomenon. Furthermore, the history is made even more fascinating because of the many famous persons linked wit,h the investigations. A recent artirle on "Fresh Water from Sea Water" by Clifford A. Hampel interestingly summarizes this story. For many centuries, numerous attempts were made to secure fresh water from sea water in order to alleviat,e the sufl'erings of mariners devoid of supplies of
fresh water and adrift on a limitless ocean. Today the lack of sufficient supply of fresh water is no longer the concern of small groups of seafarers, but it is a problem of paramount importance to many densely populated areas of the world. From some of these areas one may gaze upon tremendous expanses of water rendered useless by the presence of salts. So important is the question of how salt water may he economically made fresh that the Congress of the United States has created t,he Saline Water Program, directly under the Secretary of the Interior, wit,h the hope that an economical process will be evolved through research. Chemistry has played a major role in the development of oceanography. Useful materials have been extracted from ocean waters and marine organisms. Human beings are' dependent upon the seas for part of their food supply. Much of the weather they enjoy (or curse) is made a t sea. One notes with satisfaction the ever-growing interest in the sea and the role played hy chemists in the study of the seas. BIBLIOGRAPHY ROYLE, ROBERT,"The Works of the Honourable Robert Boyle" fed. bv Thomas Birch). 6 volomw. minted hy J. R. Rivingtnn, . iondon, 1772. FRLNKLIN, BENJAMIN, "The Work8 of Benjamin Franklin" (ed. by John l3igelow) 12 volumes, G . 1'. Putnam's Sons, New York, 1904. T., ''EmIy Soience in Oxford," 14 volllmes, GUNTHER, RDBERT Oxfwd 192345. A,, Chem. Eng. News, 26, 1982-5 (1948). HAMPEL, CLIFFORD LIEBMANN, A. J., J. CHEME D ~ I C33, . , 166-71 (10.56). MILLER, G. W., "A Compwh~n~ive Treatise on Inorganic and Theoretical Chemistry," Vol. I, Langmans, G1,een & Co., Inc., New .. . York - - . ~ -1023 , SYERDRITP, H. V., M. \Ir, JOHNSON, AND R. H. FLEMING, '>The Oceans," P~.mtice-Hall,Inc., New York, 1942. THOMPSON, THOMAS G., A N D REX J. ROBINSON, Bull. Nut. Research Coz~neil( U S . ) ,85,4R-203,(11132).
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