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The Birth of Unit Operations
Lewis matriculated at MIT in 1901. While today’s curriculum is heavy in mathematics and basic science, students in the early 1900s spent much more of their time in drafting rooms, shops, and foundries, learning how to run and repair furnaces and boilers, presses and blenders, generators and turbines. As the Institute responded to the management demands of specific industries, the goal, as the MIT catalogue explained, was to bring students “into direct contact with the material problems of [their] future profession.” By the end of the 19th century, industrial demands reflected the growing frequency with which gases and liquids were handled on a widening range of production scales, in the manufacture of such things as alcohol and alcohol products, acids, fuels, paints, bleaches, dyes, glass, soaps, oils, lubricants, metals, and gunpowder. MIT reacted to this growth by hiring several new faculty members to expand its offerings in what was then referred to as “industrial chemistry.” One of these was a farm boy from Delaware named Lewis.

When Lewis joined the faculty in 1910, the department was changing quickly. An earlier hire, William H. Walker, had been a partner with Arthur D. Little in the firm Little and Walker, one of the country’s first industrial-consulting firms. (It went on to become Arthur D. Little.) Walker’s experiences had given him an intimate acquaintance with the burgeoning chemical industries. Along with Little, an 1885 MIT graduate and a member of an MIT visiting committee, Walker knew that the days of teaching the management of specific machines for specific industries were over. There were just too many machines, changing too rapidly, organized in too many different combinations. The industrial-chemistry program was becoming incoherent; a prospective employer could not know for certain what a graduate knew. The field needed recentering and simplification.

Walker and Little had an idea of how to go about it. While modern chemical industries had become tremendously diverse, almost all drew from the same short list of processes: heating and cooling, mixing and separating, vaporizing and condensing, grinding and crystallizing, and so on. What differentiated one industry from another was the sequence in which these processes were strung together and their operating parameters – scale, temperature, pressure, rate, and so on. Walker and Little’s idea was to -refocus industrial-chemistry education on these core processes. -Little called this perspective “unit operations.”

With input from Little, Walker and Lewis undertook the mammoth task of precisely defining unit operations and figuring out how best to teach students to perform them. They faced two obstacles. The first was the challenge of reconceptualizing the science of physical chemistry in terms that made sense from an engineering point of view. To lampoon the difference between them slightly, scientists are interested in whether A causes B; chemical engineers are interested in how much of A makes how much of B over what ranges of temperature, pressure, and time, preferably to at least three digits of precision. All of that information existed, but it was buried deep in the science. Fortunately, Lewis had an immense talent for squeezing out important regularities from even the most abstract theory. (Some of his students suspected that he had devised his own system for using a slide rule to solve problems to an extraordinary level of resolution.)

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