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Jan., 1017

THE JOURNAL OF

INDUSTRIAL AND ENGINEERING

CHEMISTRY

nothing like fixed standards in length have prevailed. Kilns now installed range from 100 to 150 feet in length and have an output of from 400 to 800 barrels a day. A few kilns 250 feet in length are in operation. In line with changes in type and capacity of kilns, it is natural that there should be changes in crushing and grinding machinery which have also contributed to the enormous tonnages of raw and finished material. The cracker crushers and millstones of the early days of the cement industry have been replaced by larger and more efficient reducers. At present the gyratory crusher is almost exclusively used for the first stage of reduction. In 1905 the United States Geological Survey published as its Bulletin 243, a report of the cement materials and industry of the United States, prepared by Edwin C. Eckel. The introduction to this bulletin was written in 1904 and called attention to the marvelous growth of the Portland cement industry during the ten years preceding. Mr. Eckel then said: "In its importance to our present-day civilization, cement is surpassed among mineral products only by iron, coal and oil. In rate of increase in annual production during the last decade, even these three products cannot be compared with cement , In 1800 the total production of Portland cement in the United States was 335,000 barrels, valued at $439,050. In 1903, it exceeded 22,000,000 barrels, while the value was over $27,000,000. "During the 16 years which witnessed the development of the American Portland cement industry, two of the greatest gold discoveries in the world's history were made in Colorado and Alaska. The annual gold production of Alaska and of the Cripple Creek District in Colorado have impressed themselves on every citizen of the United States, while the Portland cement industry has attained its growth in comparative obscurity. Yet on comparison it will be seen that the gold production of Cripple Creek is only slightly greater than the output of Portland cement, while the production of Alaska sinks into comparative insignificance. Moreover, the greater part of this increase has been within the last decade. The production of Portland cement has risen from a little less than $2,500,000 in 1896 to over $27,000,000 in 1903." These figures now have only a historical interest. But they are interesting because of the growth which the Portland cement industry has undergone since they were published. In 1915 the total production of Portland cement in the United States was 85,914,907 barrels valued at $73,886,820. The recent growth of the American Portland cement industry has been so rapid that its present relative standing among our great industries is realized by few, sometimes not even by those most directly interested Nature has provided an abundance of calcareous and argillaceous materials suitable for the manufacture of Portland cement and its manufacture does not involve a secret process. Portland cement is but one of a dozen chemical compounds which harden or set when mixed with water. It has attained its great importance because of the ease and relative cheapness with which it can be manufactured and not because of any peculiar properties not possessed by certain other compounds. But simple mechanical mixing of silica, alumina and lime in the proportions usually found in standard Portland cements will not yield a compound possessing the required properties. It is essential that the ingredients be properly combined, not exactly as a true chemical compound but rather as a physical chemical solution of one or more chemical compounds in each other. The best, and practically the only way, In which such a union can be attained is by a complete or partial fusing of the silica, alumina and lime, in other words, reducing this mixture to a clinker, then grinding it to a fine powder. Knowing the chemical ingredients of Portland cement and the steps necessary to combine these materials properly, it Is evident

that plants of the Industry should be widely distributed. A mixture of clay and limestone can be so prepared artificially that when the combined water in the clay and the carbonic acid of the limestone are driven off by heat, the residue will form clinker of the desired composition. Assisted by the mechanical equipment devised and perfected by the mechanical engineer, the chemist then controls the process of cement manufacture. The Portland cement industry is a chemical industry in that Portland cement is the result of reactions going on at high temperatures between the silica, alumina and lime in predetermined proportions. For this reason it is necessary that the scientific side of the industry be given proper recognition and research work be highly developed and persistently maintained. Chemical research may be and has been directed in various directions in industries which involve chemical principles. Take, for example, the manufacture of dyes, in which chemistry, by the manipulation of coal tar, has evolved practically every conceivable color. Chemical research may also be directed toward the development of new processes or the modification of old methods. and toward a proper interpretation of the reactions to which the formation of different products are due, in order that the conditions under which they originate may be made the most favorable for producing the highest grade of material at the lowest cost. The Portland cement industry, like many other industries, has benefited because of persistent research and study along the last two lines. In the early days of its development, manufacturing processes were carried on largely by rule of thumb methods, and the preeminence of Portland cement has been made possible solely because of the control which the chemist can exercise over the finished product before and during its manufacture.

THE AMERICAN CEMENT INDUSTRY

John W. Eckert has been called the father of cement chemists in this country. While working as an assistant at Lehigh University, South Bethlehem, Pa., he was asked to make analyses of rocks from the different beds in the quarries of the Coplay Cement Works, of which D. O. Saylor was then President. Mr. Eckert was finally engaged by the Coplay Cement Works to devote his entire time and knowledge to the process of manufacture and in this way became the first cement chemist in the United States. His efforts resulted in more certainty and less chance in the preparation of proper mixtures. A more nearly uniform product naturally resulted. This was in the latter seventies. Somewhat later, Robert W. Lesley, one of the pioneer manufacturers of the country, in cooperation with George W, de Smedt, then a Government chemist, worked at various problems that had been puzzling cement manufacturers; among these was a search for something to retard the setting time. Chance brought to light the fact that gypsum added in certain quantities accomplished the desired end. But although chemistry has had a great deal to do with progress made in the manufacture of Portland cement, the work of the chemist has been most effective in perfecting technical processes. Only within the past year has it seemed likely that the chemical structure of the material will soon be disclosed. Studies now in process at the Geophysical Laboratory, Carnegie Institution, Washington, appear to point to this conclusion. The chemist has shown that a true Portland cement can be made from blast-furnace slag, once a waste product, and has thus been responsible for a great industry producing considerably over 10 per cent of the total Portland cement manufactured in the country. He has proved that the cement rocks, as found, for instance, in the so-called Lehigh district, need not be depended upon as a source of high-grade product. He has found that almost every state in the Union contains materials which, when properly combined, will product Portland cement of high quality. He U able to control even variations in composition of raw materials ami as the requirements of engineering speci-