hope. The brine in this lake carries from 5 to 6 per cent | of potash salts, but it is impossible to separate these from other material by simple crystallisation and the cost of more complicated methods is enhanced by the d fficulty of operation in the middle of a large desert. The best that is at present predicted from this source is that it may yield a small quantity of potassium salts, of uncertain quality, as a by-product in the manufacture of sodium bicarbonate, the cooking-soda of our households. As a source of potassium sulphate, the salt most used in fertilisers, a deposit in Utah of a mineral known as alunite, having a general similarity in composition to the potash alum of commerce, is of considerable ultimate promise. After roasting this mineral, potassium sulphate can be leached from the residue by water. Inaccessibility to a market for the product is, under present conditions, a limiting factor, but it is stated that there is expectation that this material will be worked for potassium salts even after competition with those of European origin again comes into play. delay but can no longer stop the development of our potash resources." While the view here expressed by Dr. Cameron may meet industrial needs, it seems evident that the Federal Government cannot afford to neglect to foster such a development as will ensure our ability to meet emergency demands such as are now upon us. Investigations should also be made to determine how far substitutes may, in emergency, be employed It has already been found that, to some extent, the land plants can be made to assimilate sodium in place of potassium, and glass-makers have, under the stress of necessity, discovered that glasses can be made from soda (which in turn is made from table salt), which possess properties which were supposed to be attainable only through the use of the more expensive potash. Cut-glass, formerly made exclusively from lead and potash, is said to be a case in point. These discoveries, in two widely differing fields, are indicative of the conditions in applied chemistry in general. Resources of Nitrogen. The third ingredient of fertilisers, already named, nitrogen, and the " nitrogen question," because of its bearing upon both sustenance and defence, is, as a matter of preparedness, the most vital of all, not excepting the selection of a system for military training of men. Privation and helplessness, even humiliation, may well be the penalties attaching to indifference to this question to-day. It is desirable to distinguish clearly between what is meant by free nitrogen and fixed ni rogen. We live in an ocean of atmosphere some six or seven miles deep, composed essentially of free oxygen and free nitrogen. This nitrogen gas exerts a pressure of about seven tons upon a single square yard of the earth's surface. Assuming an average figure for the content of nitrogen in living matter, it is within bounds to say that this amount of free nitrogen would correspond to 50 tons of living matter, provided only that the nitrogen can be harnessed for service. Finally, much has been published regarding the interesting production of potassium chloride from the socalled Giant Kelps of the Pacific Coast. These sea-algæ have the power of appropriating a considerable proportion of potassium from the sea-water, potassium chloride being always present in the ocean in small amounts. These kelp beds along the coast of the United States and Alaska aggregate more than 400 square miles. They lie within one marine league of the coast, and are therefore controlled by the States, not by the Federal Government. The plants have an average length of too feet, of which 30 to 70 feet streams along near the surface. A cutting of from 4 to 6 feet has no noticeable effect upon the harvestable area, and the cutting seems to produce a stooling effect, causing the plant to grow more thickly and heavily. It seems probable that several cuttings a year may be made without damage to the beds, and that these beds alone might be made to yield, under careful and judicious harvesting, some six or seven times the present normal demand of the United States, whenever the market price is such as to yield a sufficient financial return. The harvesting is relatively easy, although con siderable losses were sustained before the great power of resistance of this heavy wet material was demonstrated.robably explained by its intense activity towards itself. The greatest difficulty lies in drying this slimy mass, to cause the separation of the desired salts or as a preliminary to burning. The fuel expenditure in the drying process is very high. While the dried kelp is itself good fertilising material, the kelp-ash will probably command more of a market, if for no other reason than the high cost of transportation during the long haul to Eastern markets. The kelp will probably be most valuable as a source of pure potassium chloride, which is, in turn, used to manufacture potassium chlorate, an ingredient of almost all of the matches to-day, and, as recent events seem to show, an important war material. It is evident, therefore, that potassium compounds must be carefully considered in plans for preparedness, from both the agricultural and munitions viewpoints. Because of the long-recognised agricultural importance of the potassium salts the Federal Government, through its Bureau of Chemistry and Bureau of Mines, has already devoted much time to a study of our national resources as just outlined. Dr. Cameron, in commenting on this, writes as follows: "While it is undoubtedly true that Governmental efforts can yet furnish assistance, there is a very serious doubt as to how far these efforts should be continued. The time seems to have arrived when the commercial interests should themselves squarely assume the tasks confronting them and the costs of what further experimenting is necessary. This they have been slow to do, but there is rapidly accumulating evidence that these interests are responding to the spur of necessity, and that sooner or later potash salts from American sources are to be put upon the market. An early cessation of the European war might Free nitrogen is an inert substance, and serves merely as a diluent of the oxygen of the air. When we describe its properties we at once begin to state the things which it will not do. But the very inertness of free nitrogen is Free nitrogen is assumed to be made up of molecules of nitrogen, each containing two atoms of nitrogen united to each other, thus NEN. In order that free nitrogen may become fixed nitrogen, that is, nitrogen in combination with other elements than itself, it is necessary for the molecule to be broken down into its separate atoms, since chemical changes take place between atoms of the elements, that is, NEN must become 2NE. This separation is hard to effect, and conversely once effected, it is hard to maintain. More specifically still, there is a tendency for a nitrogen atom which has been induced to enter into combination with other elements to release its hold on them and to recombine with another atom of nitrogen. Hence free nitrogen is stable and indifferent, while many nitrogen compounds are unstable. Some are violently so, and are, as we shall see, our explosives; others constitute vital components of our animal and vegetable food supplies and of our own bodily structures. The latter type disintegrates, for the most part, peacefully. It is, nevertheless, their tendency to thus disintegrate which gives them their food value. Free nitrogen taken into the lungs is exhaled unchanged; but nitrogen assimilated as food becomes for the time a part of the animal body, and pisses out of the animal system in the excretions, in the form of new nitrogen compounds, formed within the body. These return to the soil, are acted upon by bacteria in the soil and converted into soluble nitrates, which then exercise manurial properties and are taken up by vegetation. The vegetable foodstuff is again eaten, assimilated, and the nitrogen compound again excreted. This is known as the nitrogen cycle, within which our lives seem to be set. CHEMICAL NEWS, Feb. 9, 1917 Chemistry and Preparedness. Aside from this supply of free nitrogen which resists efforts to convert it into fixed nitrogen, what have we at hand for use in our fertilisers, to sustain or intensify agriculture? We are restricted to soluble nitrogen compounds, essentially to compounds of nitric acid (the nitrates), and to the compounds of nitrogen with hydrogen (ammonia), and its derivatives, chiefly ammonium sulphate. The natu rally occurring nitrates of sodium and potassium are now so valuable for their yield of nitric acid or potassium that, although they have of necessity been used in the past, ammonium sulphate is probably the substancs of main significance for the future, so far as our natural supplies are concerned. The commercial source of ammonia is chiefly that of a by-product in the manufacture of coke and coal gas. When soft coal is heated in a closed retort or oven, volatile ingredients distil from it, made up of what we call coa-lgas for illuminating purposes, coal-tar, and ammonia. The ammonia is collected in water, in which it is very solable. The ammonia water thus formed is treated with sulphuric acid, and the ammonium sulphate crystallised from the solution. The annual production amounts to about 1,250,000 tons, but this is far less than the present demand, which will constantly increase. It is true that there has been an appalling waste of ammonia in the production of coke in the so-called bee hive ovens, from which all the volatile products escaped into the air, but it is plain that even if this is reclaimed it will far from su.fice in the future for agricultural needs. A minor additional source of ammonia has been found in the cremation of garbage, and in procedures for the recovery of ammonia from water-gas. How then can we tap the atmospheric reservoir for material to protect our food supplies? The bacteriologist has shown us one way by which Nature accomplishes this object by demonstrating that certain bacteria which find a residence in the nodules at the roots of leguminous plants, such as clover, and alfalfa, are able to assimilate free nitrogen from the air, and convert it into some compound which the clover, &c., in turn can assimilate into their structures. These plants can, then, be employed as miniature fertiliser factories, in situ, for, if the plants are subsequently ploughed in, and undergo decay and oxidation at the hands of other bacteria, the resulting water soluble nitrogen compounds are taken up by the next crop. This is, to be sure, a partial relief, but obviously slow and insufficient. But the chemist has discovered at least two commercially practicable procedures which are more rapid and significant. The first of these is the manufacture of cyanamide, a name which means but little to most of us. It is also known as "lime-nitrogen" and "Kalkstickstoff." This procedure has been made possible, in turn, by the develop. ment of the electric furnace. In these furnaces very high temperatures are attained by passing very heavy electric currents through the mass of reacting material, which, because of its resistance to the passage of the current, becomes highly heated, without the use of external fuel. It is similar in principle to the overheating of electric wiring by too heavy currents. Calcium carbide, made in such furnaces from lime and coal, is familiar to us as a source of acetylene gas, when treated with water. If free nitrogen is passed over this carbide under suitable conditions, it combines with it to form what is called calcium cyanamide. This, in the presence of water, gives ammonia as one of the reaction products. The cyanamide can be also used directly as a fertilising agent. Two features of this process require further attention. The nitrogen used must be nearly free from oxygen. Fortunately, methods are known by which such a separation of the two main constituents of the atmosphere can be brought about. Air can, to-day, be liquefied with ease, and the resulting liquid consists, of course, of a mixture of oxygen and nitrogen. This may be compared with the mixture of alcohol and water which we are accustomed to use in winter in the radiators of automobiles. It is wellknown that the alcohol " boils away" first from such a mixture, and the reason is that the alɔohol is more volatile, that is, bas a lower boiling-point than water. If we were to collect and examine the first portion of the vapour from such a mixture, it would be found to be nearly pure alcohol. Now nitrogen is more volatile than oxygen. Hence, if liquid air is allowed to evaporate, under regulated conditions, the nitrogen escapes first from that mixture, and such nitrogen corresponds to the alcohol above and is so nearly pure that it can be readily freed from remaining amounts of oxygen. This is, in mere outline, the way in which the free nitrogen is obtained from the atmosphere in quantity to-day, as a first step in the processes for its fixation. It is fundamental to the success of such processes as we are now considering. The second point to be emphasised is that electrical energy is used as a source of heat, and, as is well known, water-power is usually the cheapest source of energy. This process has accordingly found its chief development in Norway and Sweden. It is stated that an English company is planning the application of 1,000,000 horsepower in Norway and Iceland, in addition to the 200,000 now in use in various places, for the production of the cyanamide. It is significant that not a single factory exists in the United States, although we have much available water-power. The second chemical procedure for the "fixation of nitrogen" is the direct union of nitrogen with hydrogen to form ammonia. This has been developed in Germany by Prof. Haber and the chemists and engineers of the Badische Anilin and Soda-fabrik. The nitrogen is obtained in the way just described. The hydrogen is probably obtained by the electrolytic decomposition of water. The two gases do not readily combine, but under a great pressure of 3000 lbs. per square inch nnd at 500° C. they can be made to combine, in the presence of a catalyser, that is, a substance which merely by its presence increases the rate of a chemical change, its effect being sometimes compared to the lubricant on the works of a clock. Uranium is the substance supposed to be used in this case. That this process is a commercial success is beyond question, and it is in part due to it that Germany has not long ago exhausted her supply of ammunition, for, by another process, involving the use of a different cataly sing agent, ammonia and air can be converted into nitric acid, and without nitric acid not one of the explosives in actual use in peace or warfare could be manufactured. The world supply of nitric acid has, until recently, been derived from natural nitrate beds, composed of sodium nitrate, located almost entirely in Chile and Peru. It is known as Chile saltpetre. There is some potassium nitrate in India. The nitrates can only be found in an almost rainless country, as they are very soluble in water. Chile has an annual output of about two and a half million tons of ni rate. The United States takes from one-fifth to one-fourth of this output. It is estimated that about 50 per cent of the nitrate in ported into this country is used for explosives, 25 per cent for the manufacture of nitric acid for other uses, and 25 per cent as fertiliser. It is, of course, very valuable for the last-named purpose. Sir William Crookes, in his presidential address before the British Association for the Advancement of Science in 1898. dwelt with great earnestness upon the serious neccssity for the development of processes which should enable us to obtain nitric acid from other sources, since the visible supply of natural nitrates seemed likely to be exhausted by the middle of the present century. The seriousness of the extreme localisation of these supplies finds forcible illustration in the present situation of Germany. More than a century ago Cavendish pointed the way to what in point of time was the first commercial process for the production of nitric acid from the nitrogen in the atmosphere. He showed that nitrogen and oxygen, both, produced by prolonged oxidation at 100° is about 3-5 per cent of the initial weight of the coal. The diminution in calorific power produced by oxidation at 100° amounts to 3-13 per cent. The amounts of ash and volatile matter are not appreciably altered by prolonged oxidation. Oxidation often occurs in coals stored in heaps, and even in the mine, so that the estimation of the value of a coal from its percentages of ash and volatile matter is liable to seriour error. New Effect Relative to Thermo-electricity and to the Thermal Conductivity of Metals.-Carl Benedicks. -From theoretical considerations the author has arrived at the conclusion that the deduction made by Drude from the law of Wiedemann Franz is not admissible, and that the proportionality between the thermal and electric conductivity is due to the fact that when a homogeneous metal is heated unequally strong electric currents arise, and occasion a considerable transport of heat. He has investigated the subject experimentally, and has arrived at confirmatory evidence. He has found that the thermal conductivity of metals is not independent of the dimensions of the sample. of course, close at hand, will combine to some extent when | amount of moisture in the coal. The increase of weight an electric spark is passed through a mixture of the two gases. An oxide of nitrogen results from which, on contact with hot water, nitric acid is formed. The yield was very small and unpromising. Under the stress of pproaching need this process was studied anew. It was round that by spreading out the electric discharge by means of electro-magnets the gases could be exposed to an electric flame several feet broad, and by a suitable and regular removal of the products of the change the yield could be greatly increased. Here, again, oxygen and nitrogen are readily available, but the generation of electrical energy at a figure which would permit of a possible competition with natural nitrates under normal industrial conditions would presumably require the use of water-power to drive the generators. The first commercial plant to operate under this procedure was built in 1902, at Niagara Falls, on the American side, by two American pioneers, Mess:s. Lovejoy and Bradley, and to them belongs the credit of having furnished the first answer to Crookes's call of distress. In all probability they also laid the foundation for a development which has made it possible for Germany to challenge the world at arms. Why is this plant not in operation to-day? Simply because the authorities failed to take the slightest interest in the matter, and private capital was suddenly withdrawn. Abroad, however, the situation was different. In Sweden and Norway, with cheaper water-power, and upon the fonndation of the experimentation of Lovejoy and Bradley; backed by plenty of capital in the hands of well-advised bankers, and aided by the co operation of established in. dustries, the "fixation of nitrogen" in the form of nitric acid has been greatly developed. The best known process is that of Birkeland and Eyde, based upon the principles just briefly outlined. Directly or indirectly the Birkeland and Eyde process, and its modifications, has played a conspicuous part in Germany in the production of the required quantities of nitric acid, and must receive serious attention in our own country if we are to meet the future demands upon a peace or war footing. They the Selective Influence of Thermal and Chemical MEETINGS FOR THE WEEK. Other procedures for the production of ammonia, in which, for example, the free nitrogen is made to combine with aluminium, and the resulting nitride is treated with water, the Surpeck process, are of potential importance, MONDAY, 12th.-Royal Society of Arts, 4.30. (Cantor Lecture). but must be passed by with th's mere reference. (To be continued). CHEMICAL NOTICES FROM FOREIGN SOURCES. Comptes Rendus Hebdomadaires des Séances de l'Académie No. 24, December 11, 1916. Oxidation of Coal.-Georges Charpy and Marcel Godchot.-When specimens of coal from central France are heated to 100° there is first a decrease of weight, due to the evaporation of water; at the end of about three hours desiccation is complete, and if heating is continued the weight gradually increases. The increase gradually lessens, and ceases after two and a-half or three months. At temperatures up to 150° the phenomenon is the same, but the rate of oxidation increases a little as the temperature rises. Above about 150° CO2 is evolved, and loss of weight occurs. The calorific power of the oxidised coal is The authors have studied the considerably reduced. phenomena quantitatively with fourteen samples of coal Town Planning and Civic Architecture," by Prof. Biochemical Society, 5.30. (In the Institute of TUESDAY, 13th.-Royal Institution, 3. "Pain and its Nervous Basis," by Prot. C. S. Sherring on. WEDNESDAY, 14th.-Royal Society of Arts, 4.30. "Highways and Footnaths," by Lawrence Chubb. Royal Society. "Structure and Development of Society of Glass Technology, 4 30. (At the Univer- Seventeenth Century," by Very Rev. H. Hensley from St. Eloy, Noyant, and Ferrières. They find that FRIDAY, 16th -Royal Institution, 5.30 "Author's Dedications in the the loss of weight on heating for three hours to 100° is practically identical with the loss of weight on drying in vacuo at the ordinary temperature, and represents the SATURDAY, 17th.-Royal Institution. 3. "The Mystery of Counterpoint," by H. 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