On PREPARATION to DEAL with SOLUBLE SILICATES* JAMES G. VAIL Philadelphia Quartz Company, Philadelphia, Pennsylvania
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The maker of sulfuric acid builds towers and tanks of vitrified brick set in acid-resisting cement made from powdered quartz and silicate of soda which must be of the right ratio and concentration to give proper setting time and ultimate strength. The maker of abrasive wheels starts with a silicate of entirely different type, uses different mineral additions, and develops the bond a t 350' to 400°F.instead of atmospheric temperature. Factories which deal with foodstuffs, dairies, canneries, and packing houses must be kept scrupulously clean. The soluble crystalline silicates are used for these purposes either alone or in combination with other cleaning agents; criteria of grease removal to freedom from the so-called water break, elimination of living bacteria, and the study of etching effectson metals are involved. Silicate solutions act as fireproof adhesives for making air-cell pipe covering from asbestos paper. Viscosity control is essential to regulate penetration. Electro-cleaning preparatory to plating is advantageously done with silicate solutions, usually more or less modified with other materials according to the rather complicated requirements of that art. The soap maker produces a colloidal complex containing silicate which must not only have cleaning power but must form a cake of acceptable appearance, neither too hard to dissolve nor soft enough to waste away too rapidly. It must be free from unsightly efflorescence. Some understanding of this art is expected of the purveyor of the silicate. The refiner of edible oils useasilicates on occasion to increase recovery by causing the separated impurities to settle into denser form. He also puts a silicate film on wooden casks and tubs to prevent penetration and loss of oil in transit. Factory floors of cement are oil-proofed and hardened by silicate treatment. The best results require an understanding of the possibilities and the limitations of the process, and the right silicate. Base-exchange water softeners are made by reacting silicate solutions with aluminum compounds. The list could be greatly extended without torture of the facts. It is evident that a great diversity of questions will, under such circumstances, be presented for solution. Specifications must be devised and degrees of control established having regard on the one hand to the needs * Presented at a joint meeting of the Industrial and Engineer- of the consumer, and on the other to refined questions ing Section and the Chemical Education Section of the Canadian of economy, for the soluble silicates owe their place in Chemical Association at Toronto, June 6, 1934.
N THE complexity and change with which we are surrounded, it is sometimes useful to approach an inquiry in a relatively simple way by beginning with facts of which one has direct experience before attempting to draw conclusions of larger scope. Thus it may be worth while to consider the sort of intellectual equipment that appears to be useful to chemists and chemical engineers in certain particular circumstances, and to reflect later whether the findings have general significance. The person whose preparation is here considered is not the hatchet-and-saw man of chemical technology, but the worker of independent thought whose function i t is to initiate and lead. It is not unlikely that in working with soluble silica+-, developing their diverse properties, and seeking ways to adapt them to the needs of industry, technically trained men exercise their powers upon a stage where only the setting is distinctive; the action may be more or less typical. We shall attempt a brief survey of what is on the boards. Industrially speaking, the soluble silicates may be restricted almost to the three-component system, sodium oxidesilica-water, for the use of potassium silicates is very limited and silicates of other alkali metals are for the present not used in significant amounts. It has been suggested that the content of this one triaxial diagram is too small an area to engage the efforts of a group of able workers. The idea was not born of insight. The substances within this category have what may be called "a degree of uniquity" such that there is scarcely an industrial establishment which does not, somewhere among its operations, have use for one or more of the numerous products grouped under the family name of silicates of soda. By calling to mind a few of many processes we can better see what abilities are needed to deal with them effectively. The paper maker adds silicate solutions to the pulp during beating, precipitates them in the presence of alum, and gains hardness, finish, and retention by working a t the appropriate pH. The pottery in which heavy sanitary ware is cast deflocculates clay slips with silicate and is thus able to handle as liquids water-clay mixtures with much larger solid content than would otherwise be possible. Capacity is thus increased, texture improved, and losses from crack in^ reduced.
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industry to the fact that they are available at low cost. The most economical raw materials must be found, the best sources of supply developed for widely separated points of production, methods of purification must be studied, technic developed in the choice and application of refractories, and then in order to establish markets, technical services must be made available to the distributing organization. Such situations are replete with opportunities for initiative, resourcefulness, and energy, though it is not always possible to finance the various researches which are so easily suggested. Because the equation must be solved for the factor represented by the dollar mark, the choice of projects and the effective use of time are important. One method of conserving energy is the systematic assembly and graphic expression of those data which underlie many specific cases. Such are the determinations of relationships between composition and properties. For instance, the densities of silicate solutions which result from the presence of varying quantities of alkali, silica, and water must be mapped and iso-viscosity lines located. Such values as refractive indices, boiling points, freezing points, and volume changes with temperature, are less predictable than in systems in which stoichiometric boundaries can be uniformly depended upon. The worker in this field must, to a great extent, devise means for collecting his data and evaluating the degree of precision attained. Then he must find ways and means for making it intelligible to others. The departments of science which can assist him are numerous. An important use of silicate solutions is their application as adhesives for uniting solid fiber board to make shipping containers of three- to five-ply laminated construction as well as the familiar corrugated type. The mechanism of adhesi\.c action has not been adequately worked out from a scientific standnoint, hut it is well known that colloids, capable of passing quickly from a liquid to a solid condition, are among the most useful materials for such purposes. The fitness of silicate solutions for a given adhesive use is determined by the ratio of alkali to silica, by the amount of water present, and by added materials among which finely divided clay has of late assumed ncreasing importance. Adequate preparation for work on such a problem would include an understanding of the general phenomena of colloid chemistry and a certain ingenuity in devising methods of physical testing which, while they may not be susceptible to interpretation in absolute terms, yet give measures of the behavior of the adhesive under conditions of service. The transition from liquid to the solid state by loss of moisture occurs at different rates with diierent alkali-silica ratios. Ratio also affects the rate of viscosity change with changing temperature, the solubility and the wetting power of the adhesive film, and the tendency of the alkali to migrate through the fibers under warm, moist conditions. Ways have been found to minimize the disadvantages of an alkaline adhesive and it is possible by causing the
films to dry in place and by keeping the sodium oxide per unit of area below certain critical limits, to obviate staining troubles, work at a high degree of economy and at high speed while retaining the advantages of a mineral adhesive. Service in this area involves the ability to think of the silicate solutions as colloids. Though the colloidal sodium silicates have the longer history in industry, definite crystalline products have in late years evolved from laboratory curiosities into standardized industrial commodities. To deal effectively with these, the ability to think in terms of the phase rule is needed. I t is a matter of some difficulty to shiit one's mental gears from systems, the value of which rests upon the f a d that they are not in equilibrium, to interpretations of solubilities, transition points, stable phases, liqnidus temperatures, and the like, especially when the same components are involved in the two cases, but both colloid and phase rule viewpoints are essential to the understanding of the soluble silicates. Heterogeneous arrangement and changing states of aggregation on the one band, and the mathematical precision and beauty of crystal structure on the other are alike important. The art of removing foreign materials from snbstances to be cleansed is progressing toward a science, and silicate solutions have been established as important reagents for a multitude of cleaning purposes. Here the worker must know something about deflocculation, electrolysis, film formation, emulsification, and again must be able to resort to empirical methods for the appraisal and comparison of phenomena which cannot yet be expressed in terms of interfacial tension or other d i d measurements of fundamental characteristics. Silicate solutions are extensively used in textile processes, such as the boiling off of cotton, the weighting of silk, and the peroxide bleaching of all the natural fibers. A speaking acquaintance with microscopy and organic chemistry is needed here. The use of high-temperature furnaces for melting calls not only for consideration of heat transfer and heat balances, but also for the thermochemktry of hightemperature reactions. Available materials must be studied, as none is known which is unattacked, and each melt constitutes in some degree a separate problem. Not only refractories, but silica supplies make it extremely convenient to have some understanding of economic and physical geology. Although silica constitutes about sixty per cent. of the lithosphere, its occurrence in suitable form for the present purpose is rather limited. Most of the deposits are contaminated with compounds that form insoluble silicates, and some which are very pure but massive are excluded by the expense of mining and crushing. The cost of transportation is often a decisive factor. Means of mechanical separation of minerals have been worked out, especially in connection with the recovery of metallic values. They have also proved important in freeing silica sands from small amounts o: heavy minerals. I t may be that a chemical executive should not be
too good an analyst on account of the risk of losing perspective, but he should understand analytical procedures and know when existing methods are adequate and when new ones must be devised. I t goes without saying that he should have a general understanding of the unit processes, most of which will be frequently encountered. He needs a sense of order and arrangement, the capacity to keep his own records and to find and make use of information available through technical literature. He must be able to write a clear and concise report and to discriminate between the significant and the trivial aspects of a situation. The report should habitually appear on time. The ability to write as an item of technical equipment is often undervalued. No matter how sound a man's ideas may be they must, almost without exception, be established in other minds in order to become effective. They will be lost if badly transmitted. The use of language in clear and effective form is not wholly the business of forming sentences which are grammatically correct-it is to some extent the product of an intellectual background and a mental attitude enriched by familiarity with great thought and great writing in varied departments of human interest. A fluent reading knowledge of German is greatly to be desired not only to render accessible the large body of pertinent literature which is not translated or is rendered into English long after its first publication, but to obtain the stimulus of different thought patterns and different approaches to problems of common interest. Other languages though valuable are less important as far as soluble silicates are concerned. These requirements may seem too great to expect of one individual, but they are drawn from practice rather than theory. It is quite apparent that no school could anticipate the specific situations which will be encountered. To attempt it would be to waste valuable time and to tum out men of narrow mind-technicians rather than men of science. Four years are all too short to gain a concept of the fundamental principles of the sciences upon which chemical manufacture depends. We want men who are well grounded in what is known of theinner mechanismof materials and their behavior and who are able to organize their thoughts and carry through attacks on difficult problemsnot men who have learned routines. Early specialization must almost inevitably be at the expense of scientific breadth and soundness. I suspect it is better to approach the end of a college course without knowing definitely what industry one will enter. The agnostic state of mind is much to be desired. It should welcome new ideas and examine them with critical intelligence, it should not attach undue sanctity to methods which however good are, like machinery, subject to obsolescence. For all this, understanding is required and the academic years are too short to admit of courses the content of which any competent person can pick up on his own account. Assuming that a man has sufficient background to become proficient or to collaborate effectively with
those who are proficient in the various skills which have been indicated, he may yet lack essential qualities. Unless through all the maze of detail he is able to acquire a sense of direction, an orientation and insight into the course which is worth pursuing and that which should be abandoned, he will not achieve effectiveleadership. In addition to knowledge, he must have "horse sense." A figure of reference to migratory birds or the instincts of bees might bear a more appropriate couuotation. Although this sense is to some extent congenital, I submit for your consideration that it is the men who have a broad general knowledge who are most likely to succeed in a development project which includes the finding of new industrial procedures, and this broad knowledge rests, in turn, upon a curiosity which can be cultivated. Teachers can do much to help a man realize what he must acquire for himself. The idea that successful men are, almost without exception, masters of large vocabularies has been recently advanced and supported by a persuasive body of data. A large vocabulary would be apt to result from a breadth of interests, and a wide range of ideas should afford a better opportunity to develop perspective and to chart wisely the course of an industrial enterprise or a research project. A man ought to leave college knowing that his education has only begun. The scope of this paper does not permit examination of the elements of personality which make for successful cooperation, but for leadership in the cooperative business of finding the way in the maze of modem industry the observation of soluble silicates has impressed upon the writer the need of the best possible perspective. This word is used in a broad sense and involves something more than an understanding of the technology of a diverse and changing industry. Perspective in space is more readily obtainable today than when island universes and subatomic phenomena were not extensively presented in the public press. In a less degree perspective in time is now to be had as a part of one's general intellectual background, but we still meet many people who, as a practical matter, live within a time horizon of relatively few years. To them the invention of the steam engine seems to have occurred a long time ago and occurrences which lie beyond their individual prospect of survival have little interest. More distant events in either direction appear, if at all, as through a glass darkly. Perspective in both time and space is, however, believed to be an essential of equipment for adequate leadership. I would go farther and say that men without perspective in human experience, as revealed through history and philosophy, will as leaders labor under a severe handicap. The necessity for social readjustment which is one of the clearest signs of the times may lead to confusion and a vast waste of energy in a leader thoroughly read in science but unacquainted or unconcerned with the humanities. The question of leisure time for himself and those he leads will be enormously complicated for the man who has technic but not perspective. Orientation among scientific facts is difficult enough but
obtainable by a person of requisite curiosity, intelligence, and energy. Orientation in other departments of knowledge may not, at casual glance, seem so important, but the man who comes out of college aware that the experience of his species in many departments of life and thought can illuminate his personal outlook and understanding is certain to apprehend more surely than the specialist who sees only in terms of his specialty. One may think of the latter as having a two-dimensional frame of ref-
e r e n c e i t is the points in the third dimension and beyond by which the fullness of the picture may be perceived. I t takes more than plane geometry to comprehend the structure of a crystal. The conclusion seems obvious, but the excuse for reiterating it is that there are still people who do not know that a technologist may be a better servant of industry as well as of his neighbors by cultivating his curiosity about such things as art, archaeology, psychology, politics, philology, and I should not exclude comparative religion.
