SEPTEMBER, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
been utilized in the past. If it were made compulsory to collect and detin used cans, there would be an annual recovery of 10 to 20 thousand tons of pig tin. If the worst imaginable condition should arise and all external supplies should be shut off, and if our reserve and recovered tin were not sufficient to meet requirements, methods of manufacturing cans of plain steel plate, or a t least with greatly curtailed use of tin, would have to be perfected. Preparation to manufacture tinless cans for food packing mould involve a major change which would present great difficulties to the industry. The magnitude of the difficulties would depend upon the degree of reduction in the use of tin that would become necessary. By virtue of recent improvements in the quality of base plate, a reduction in the amount of tin used in coating plate for food cans could be made, as an emergency measure, with little departure from present methods of operation, and without substantially impairing the effectiveness of the cans in preserving the quality of foods. A further material saving in tin could be accomplished, without major alteration in manufacturing methods, by using tinless steel plate or tin plate with a reduced weight of coating for some nonedible products for which regular tin plate now is used. Tests have indicated that the quality of many canned foods will not suffer if black steel plate cans, protected by enamel, are substituted for tin plate cans. Further technical developments will be necessary, however, before all products can be packed successfully in tinless steel cans. Protecting processes alone, such as the phosphating or Bonderizing process and the chromium process, are not regarded as adequate to give steel plate the required amount of resistance to chemical attack by some foods. Phosphating treatment in combination with a baked enamel coating, reported to be used on food cans in Germany, appears to be adequate for some products. For some applications nonmetallic materials, such as glass and fiber, will receive a full share of attention as possible substitutes for tin plate, in case a shortage of tin becomes acute. INKSAXD PROTECTIVE CO.4TING h/IATERIALS. During the past seven or eight years tremendous advances have been made in the development of synthetic resins. These mate-
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rials have come into use in the manufacture of both printing inks and materi$s. used in the protective coating of metal containers. Jd the case of inks, synthetic resins have already been used to such an extent that no serious difficulty is anticipated if the foreign supply of natural resins should be cut off entirely. -4lmost the same condition exists with respect to protective coating materials in so far as resinous ingredients are concerned. The extent to which vinyl resins have come into use as ingredients of these materials is indicative of the possibilities along this line. Work still has to be done in perfecting synthetic resins having the resistance to heat treatment which is required for use in connection with some canned products. Much progress is reported, however. Another type of imported raw material that is extensively used in manufacturing lacquers is Chinese tung and perilla oils. Production of these oils is now practically under Japanese control. The finding of suitable substitutes seems to be more difficult than that of substituting for the natural resins. Nevertheless, some oils produced in the western hemisphere have been studied with fairly satisfactory results. There are large reserve supplies of all raw materiaIs needed for lacquer production, and these supplies are being increased daily. Therefore, time is still available for perfection of domestic production of substitutes for these materials in case their use should become necessary. The basic ingredient of many sealSEALIXG COMPOUNDS. ing compounds is rubber. Natural rubber is another of the important raw materials of American industry for which we are dependent upon foreign sources of supply. As in the case of tin, a high reserve supply of rubber is being accumulated under the direction of the Advisory Commission for National Defense. The results of attempts to substitute various synthetic rubbers for natural rubber in sealing compounds have not been altogether encouraging. Indications are that some other domestic materials, such as synthetic resins, might be used. Sufficient progress has been made toward the solution of problems that must be faced if the use of natural rubber in sealing compounds should have t o be discontinued, to remove reasons for serious apprehensions of possible interference with the operations of the industry by such a contingency.
TANTALUM ROBERT J. AITCHISON Fansteel Metallurgical Corporation, North Chicago, Ill.
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AXSTEEL’S function in the chemical industry is to manufacture acidproof equipment which is used in heat transfer processes involving heating, evaporating, cooling, condensing, and absorbing such reagents as hydrochloric and nitric acids and their compounds, many of which are used in the manufacture of explosives and materials of chemical warfare. I n all such equipment which we manufacture, the elementary metal tantalum is used in vital spots to resist corrosive attack and transfer heat efficiently. Several months before hostilities began in Europe, the management realized the necessity of fortifying our sources of ores and raw materials, and constructive steps were taken. Inventories of high-grade tantalum and tungsten ores were increased, and favorable contracts were consummated assuring large stocks of ore for an extended term. New sources of supply for tantalum ore hare been uncovered in the United
States and other parts of the western hemisphere, largely as a result of intensive prospection sponsored through our company. To facilitate the design and manufacture of special chemical equipment, additions have been made to our research engineering and sales staff. Understudies have been trained or are being trained for important technical positions in our organization. The result of this work in the past eighteen months undoubtedly will prove helpful and necessary in connection with the current defense program. Since this company is the only producer of tantalum in the United States, and since i t mould probably take months or years to duplicate its activities elsewhere, our important position is fully realized and every necessary step is being taken t o assure continued smooth operation, with provision for expansion of facilities.
