September, 1926
IXDUSTRIAL A N D ENGINEERISG C H E M I S T R Y
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Chemistry’s Contributions to the Fertilizer Industry’ By J. E. Breckenridge THEAMBRICAN AGRICULTURAL CHEMICAL Co., CARTERET, N J.
HE fertilizer industry for the past fifty years has been engaged in procuring and making available for plant growth the elements which are continually being taken from the soil. Chemistry has accomplished much in the development of this industry. Problems have been solved and manufacturing processes have been investigated and regulated by careful and systematic chemical control.
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Perfection of Acid Phosphate Manufacture
To make available the phosphate which existed in many parts of the country and on some of the islands became one of the early problems. Phosphate rock as found on the island of Navassa was shipped to this country in the early days. This material presented difficulties when sulfuric acid was added to make acid phosphate. The content of iron and aluminum phosphate was so great as to require excess sulfuric acid, and as a result, although the insoluble phosphoric acid was low in percentage the day after mixing, it would gradually increase and t,he material in storage would set so hard as to almost defy the pick, so that dynamite was often necessary. Chemistry, together with experience, showed the industry that the high percentages of iron and aluminum oxides with small percentages of carbonates were not only difficult to handle but almost prohibitive from an economic standpoint. This condition was improved when the Soutjh Carolina deposits were found. The chemists were consulted to advise the capitalist as to the content of the newly discovered rock, and soon the South Carolina phosphate mining industry was established. Here, it was found that the water-soluble phosphoric acid content of the acidulated rock would not remain constant, and again the chemist showed them that the nodules of rock must be washed to rem0J.e the clay material and so keep the iron and alumina content a t a minimum. This washing accomplished a double purpose, it reduced the iron and alumina and increased the phosphate of lime. Florida rock soon appeared to compete with that from South Carolina, as it had low percentage of alumina and high percentage of phosphate of lime, together with carbonate of lime-all of which helped to produce a very marketable acid phosphate. While in the early days acid phosphate manufacture was largely by rule of thumb, it is now based on very strict chemical control. The rock is watched for fineness, the acid for uniform strength as to gravity and acidity; the proportions of rock and acid are carefully regulated, and the whole mixing apparatus is watched to insure a proper temperature in the mixer and that the fans draw properly. Chemistry has now made possible a volatilization process for phosphoric acid, in which iron and alumina do not interfere so seriously as in the wet mixed process, thus allowing the use of low-grade phosphate rock. Already phosphoric acid made by volatilization is on the market, but as yet it cannot compete as a fertilizer material. The high analysis fertilizers may demand that methods of manufacture of acid phosphate be changed, and here chemistry must come to the aid of the industry. It is a matter of speculation as to whether or not concentrated salts such as ammonium phosphate will replace ammonium Received May 1 5 , 1926.
sulfate. Bmmonium phosphate is already being sold as a fertilizer material and is in demand for long shipments and for making high-analysis fertilizers. The time may come when phosphoric acid can economically be used in place of sulfuric acid in fixing ammonia. Sulfuric acid of high quality is necessary for good acid phosphate. Gravity, which in the early days was the only test made, cannot be used as a criterion of quality, as sulfate of soda solution made from the waste salt cake has been known to be used to bring gravity to the required strength and the manufacturer baffled as to why his acid phosphate was damp and sticky. Now the percentage of actual dissolving power is determined. Harmful Materials Rendered Useful
I n the manufacture of acid phosphate the fluorine gases, which are harmful, were once discharged into the air, and fertilizer plants were compelled to absorb these gases. They are now condensed and recovered as hydrofluosilicic acid and find their way into various industries as salts of this acid. The smelters in the West have condensed their fumes and made available sulfuric acid, which in turn is used to make phosphoric acid, which finds its way into the industry as double superphosphate. Chemistry here has changed harmful materials into commercial articles. Supply of Nitrogen Increased
Chemistry has played a very important part in securing nitrogen and making it available for the fertilizer industry. I n the early days, fish, guanos, and packing-house tankage were largely used as organic ammoniates, but soon these materials could not supply the demand. Packing-house products found their way into feeds, leaving only the crudest organic nitrogenous materials. The fertilizer industry was therefore called upon to use waste organic nitrogenous materials. This was a decided advantage to the farmers in that i t increased the supply of organic nitrogen and so helped to regulate prices. The nitrogen problem was solved by making what is known in the trade as ammoniated base, a mixture of rock, sulfuric acid, and organic ammoniates. Xot only the state, but federal chemical investigation as well, was undertaken with the result that the process was approved and the quality of the nitrogen was materially improved. Plot experiments confirmed its efficiency, base-goods nitrogen giving results equal to blood. Activated sludge made from city sewage is making available many units of nitrogen that were formerly lost. As a result of the attempts to increase the amount of organic nitrogen, the need of a method for classifying this material arose. Such a method has been worked out by the cooperation of state control and industrial chemists. This method, however, cannot be used for too close a classifying but is useful in identifying inferior quality. Thus chemistry has given us a measure whereby we judge what returns in crops we can expect from nitrogenous materials. With the demand for high-analysis fertilizers we must consider the use of waste materials now employed and the question of withdrawing from the trade a great many units of nitrogen.
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Here again chemistry must find a way to use these units of nitrogen in a more concentrated form. Chemistry has added to the supply of nitrogen through the air nitrogen products, and in cyanamide we have a material which is able to compete successfully with sulfate of ammonia or nitrate of soda. Urea, also, a recent commercial product, is the result of chemical research. Leuna saltpeter, which has its nitrogen in the form of ammonia as well as nitrate, is available for the industry, due to chemistry, and makes a valuable product. American Potash Made Available
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During the recent war we realized our dependence upon potash. Borax came into the fertilizers through the potash salts and nitrate of soda, which carried a considerable percentage of potassium nitrate. I n the mad rush for potash during the war the percentage of borax was neglected and caused much crop damage, and ultimately legislation. Here chemical control guarded the farmers and reduced the harm to a minimum. All along the line chemistry is safeguarding the industry and protecting the farmer by seeing that harmful materials shall not be used in fertilizers. Many attempts were made to treat feldspar and other silicates of potash in order to render the potash watersoluble. Some success was experienced by mixing finely ground spar with rock and sulfuric acid, taking advantage of the fluorine liberated to assist in rendering the potash available, but the product could not compete with the natural salts. Many patents exist for furnace processes, but none are economical. The Government has made extensive investigations to secure an independent source of potash. Chemistry has, however, rendered great assistance in producing potash from the salt lakes by processes ably worked out under the direction of one of our American chemists.
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while all the potash would show water-soluble when first mixed, the content of potash soluble in water would gradually drop until after a month there would be a loss of about 10 per cent water-soluble potash. This was because the fertilizer was slightly acid when first made and dissolved the silicates and fluosilicates of potash which formed, but when the materials had been together a month this slight acidity no longer existed owing to the curing of the fertilizer, and some potash became insoluble. Methods of analysis have been revised and this revision, together with change in factory operation, has saved potash to the industry. Bags Preserved One of the early problems in the industry was the preservation of the fertilizer bag. Well do I remember our superintendent bringing in some very dusty fertilizer and saying that the bags into which it had been put the night before were so rotten that by taking hold of the ears the bag would part in the middle. Chemistry came to the rescue and found that the hydrochloric acid gas liberated by the action of the phosphoric acid on the chlorides in the potash salts was deadly to burlap. Silicates, paraffin, etc., were used, but when the bag was treated with a lime salt so that there was sufficient lime in the burlap to neutralize the acid gas, the bag remained strong. The lime salt answering this requirement was acetate of lime which, in neutralizing the hydrochloric acid gas, gave acetic acid, perfectly harmless to burlap. Chemistry Important to Profits When we consider the varied materials the fertilizer industry is now called upon to use as compared with the early days of the industry, we see the greater need for careful and accurate chemical control. The fact that in the early
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Figure 1-A
Crop where No Fertilizer Was Used
The separation of potash and borax presented other problems, but these have been so successfully solved as to give us today a potash salt equal in every way to foreign potash, and which is successfully used in a large area. Potash Saved t o t h e Industry I n the early days of mixed fertilizers, rock, acid, tankage, and potash salts were all mixed together in the mixer. It was found necessary to figure a t least 10 per cent over the guarantee on potash in order to be sure that the goods would test full to guarantee when in the trade. Chemistry found t h a t some of the potash soluble in water became insoluble when mixed with rock and acid. Investigation proved that,
Figure 2-Crop
where Base Goods NitroZen Fertilizer Was Used
days many materials were purchased on a flat basis whereas almost everything is now purchased on analysis, emphasizes the importance of such control. By careless chemical work a company’s profits may soon disappear and red figures appear on the balance sheet. The problem of mixing various materials such as sulfate of ammonia, cyanamide, nitrate of soda, and acid phosphate to make complete fertilizer makes chemistry necessary if we are to conserve plant food elements and still give the crop the required nourishment. We therefore conclude that chemistry has been instrumental in perfecting the processes, saving waste materials, making more nitrogen and potash available to the industry,
September, 1926
INDUSTRIAL AND ENGINEERIA-G CHE-VIXTRY
preventing losses of plant food and bags by faulty operation, with the ultimate result of profits to the industry. Further Problems for Chemistry
Whether or not chemistry will solve the problem of concentrating plant food elements by eliminating the excess material other than what is recognized as plant food without destroying the real agricultural value of materials, time and experience can only tell. We must, however, guard against what is well illustrated by the old story of the professor, who talking to a group of
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farmers, said: “Gentlemen, some day your fertilizer will be delivered to you in pellet form which you can put in your vest pocket. One inquiring farmer replied ‘Yes,’ and can we put the crop in the other vest pocket’?” Conservation is necessary, concentration perhaps, but let us be sure that some of the materials now used which have plant food elements in less concentrated forms do not carry elements which, while they may not be direct plant foods, have an influence on conditions which make for real fertilization, with the ultimate result that the crop secures its nourishment from a source which can be best assimilated.
A Half-Century of Progress in the Glass Industry‘ By George W. Morey GEOPHYSICAL LABORATORP, WASHI~YCTOS, D. C.
HE art of the glass-maker dates from the earliest antiquity. Its beginnings are shrouded in mystery; whether the first glass-makers were the Phoenicians, who undoubtedly carried on a considerable nianufacture, or whether the credit for founding the industry ip to be given to earlier Egyptian priests, is a moot question. Certain it is that glass objects, of essentially the coniposition of modern plate or bottle glass, have been found in tombs dating back to 3500 B. C. Glass was known to most of the early civilizations of historic times. Memphis was a glassmaking center; Alexandria possessed glass factories, producing not only blown ware but also splendid mosaics; and Rome was long a center of the art. The glass-makers’ guild a t Murano, near Venice, was a descendant of the Constantinople craftsmen, and Venice developed into the dominant glass center of medieval times. The industry was established in France and Germany in the fourteenth century, and the invention of cast plate glass was made in the latter part of the eighteenth century; the great plateglass works of St. Gobain finds the beginnings of its history in this invention. But during all these centuries only one type of glass was known, soda-lime-silica glass, modified, of course, by the very considerable amounts of impurities that crude manufacturing methods made unavoidable. Cntil recent times glass manufacture has been based on tradition as opposed to scientific knowledge, and the beginning of the period of knowledge was only fifty years ago. Before that time, to be sure, the types of glass had been increased by the addition of potash to the soda-lime crowns, and by the discovery of the flint-that is, lead-containingglasses. Some pioneers, notable among them Faraday, Harcourt, and Fraunhofer, had attempted to broaden the basis of glass technology by the introduction of other chemical elements. These early attempts were without influence upon manufacturing practice. Not until Schott began the systematic studies which were to develop into industrial practice can the modern period of glass technology be said to have begun. It may be thought that the achievements of Schott and Abb6 and their co-workers a t Jena have been over-emphasized in the historical literature of glass-making, but they represent a development which is not to be minimized. Before their time glass compositions were restricted to the crown-flint series, varying from the crown glasses, containing lime and silica with either soda or potash, or both, to the alkali-lead-silica glasses. Contrast these five oxides with the present ingredients available to the glass-
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maker, which, in addition to those just named, include barium oxide, boric oxide, magnesia, alumina, zinc oxide, antimony oxide, phosphoric oxide, and fluorine. Most of these additions to glass-making materials were made by Schott, and of them the most noteworthy are boric oxide and barium oxide. Barium oxide has had its chief application in optical glasses, and our modern high-speed lenses were made possible by the development of the barium crowns and flints. Boric oxide also is an essential ingredient in many optical glass types; but more extensive are its applications to industrial glasses, laboratory glassware, and thermometer glass. Laboratory Glassware
The development of laboratory ware is of particular interest to chemists, and no field of glass technology has witnessed greater strides. Stas realized the necessity of more resistant laboratory ware for those atomic weight researches which still command our admiration, and in 1868 he caused experimental meltings to be carried on under his direction until a satisfactory glass was obtained. But the industry was not yet in a position to appreciate the need, and until Schott again took up the problem resistant laboratory glassware was not on the market. The glass developed by Stas was a potash-soda-lime glass, high in silica, and difficult to manufacture. The Jena workers studied the effect of addition of other ingredients, and the alkali-zincalumina-borosilicate glasses, typified by the well-known Jena “Gerate,” were the result. It is a n interesting fact that for most of the uses to which glass is put the quality is better the greater the number of ingredients. This is easily explicable in the matter of tendency toward devitrification, but why it should be true of chemical resistivity it is hard to understand. The excellent qualities of glasses of the type of Jena Gerate speak for themselves, and they remained the standard for many years, until the development of the American glass, Pyrex. This also is a borosilicate, but is exceptionally high in silica (over 80 per cent), is almost alkali-free, and has a low thermal expansion. Thermometer Glass
Another problem whose solution is largely the work of Schott and his co-workers is that of a satisfactory thermometer glass. Here it is no longer true that in many ingredients there is safety, for a satisfactory thermometer glass contains but one alkali oxide, Whether it be potash or soda seems to make little difference, but a mixed soda-
