Each autumn students enroll in Chemistry 2, expecting a tough and boring semester of inorganic chemistry. By January they know that they were right about the course's toughness, but few call it uninteresting. Associate Professor Leonard K. Nash enlivens his courses by sprinkling lectures with graphic experiments. Tinker toys show the electron configurations of the elements to Natural Science 4 students, and Nash proves the explosive quality of hydrogen by turning a flamcthrower on soap bubbles filled with the gas.

But Nash admits that his steady stream of conversation during an experiment sometimes interferes with his concentration on details. Chemistry 2 alumni still talk of the day that he forgot to put a sheet of asbestos under a plate of white phosphorus. When the phosphorus ignited, Nash had to dash from the room with the flaming mass before it spread over Malinckrodt. Chemist Nash grumbles that "if things possibly can go wrong, they do go wrong precisely when they can do the most harm."

While his lectures are memorable for their humor alone, it is Nash's interest in students that has made Chemistry 2 and Natural Science 4 so popular during the past five years. Remembering his own undergraduate tussles with gram-atoms and molecular weights, he turns his sympathy for student confusion into an active program of help. Although he has an audience of several hundred, Nash frequently stops lectures to answer questions from the floor. Often he climbs on a chair in the front row to ask what is troubling a boy looking puzzled in the back of the lecture room. His lunch hour is usually spent answering the questions of students who have remained after class, and on his office door is the sign "Don't knock--walk in." Several hundred pages of notes and problems that he has prepared help to clarify the laboratory experiments. As one student put it, "When one of his students flunks Chemistry, Nash probably lays awake nights worrying about it."

But Nash was not always concerned with juggling the elements and comforting confused students. Eighteen years ago he came to Harvard from New York City as a mandolin virtuoso resolved to concentrate in English. A year with English I convinced Nash that composition and literature were not for him, so he tried Chemistry. Here he found his field, and he graduated summa cum laude in 1939.

After graduation he worked on his Ph.D. theses under Professor Gregory Baxter. Baxter at that time was studying events in outer space, and Nash's thesis became a study of the gases in meteorites. Today, one of the country's foremost gas analysts, Nash calls his unusual sorcery "Analysis of What Goes Up the Stack."

Nash completed his thesis with Baxter in 1944, and worked for a year with Professor Urey at Columbia separating from Uranium-238 the atomic bomb-ingredient, U-235. But Nash was mainly interested in teaching so when the war ended, he first spent a year at Illinois, then returned to his alma mater in 1947 as an instructor in Chemistry. He received an appointment as Assistant Professor the following year. And he made an immediate name for himself by riding a bicycle to lectures, armed with a water pistol filled with ammonia to keep the dogs at bay.

In contrast to his robust lecturing, Nash leads a quiet home life. He bought a modern home in Lexington last year, and now devotes his spare time to gardening. Nash finds that frequent revisions of his lectures seriously cut into gardening time, and his project to raise carrots for his two children has largely been abandoned to the local rabbits. Although his material varies to suit each year's students, the last lecture of his courses is always of standard brilliance. Last year, for instance, Nash created an iodine smoke screen to cap his performance in Chemistry 2. The purple vapors rising from the lectern obscured him, and when the violet smoke settled, he had vanished from the platform for an other year.