CHEMICAL
Superanhydrous iodides. One of the enterprises Sylvania runs to bring in a buck is a light bulb operation—as you may suspect if you are alive and residing in the United States. We supply various bits and pieces of tungsten and molybdenum that go into Sylvania lamps and occasion ally are called upon to provide something even more esoteric. A very, very dry iodide, for example. You can pick up iodides in the chemical marketplace that bill themselves as anhydrous but actually contain about 2% water. Inside a hot lamp, this modicum of H2O becomes an embarrassment, especially the Ο part. It tends to com bine with refractory metals with a great deal of enthusi asm and disastrous results. So we produce a sodium iodide (Nal) that makes bone dry look dripping wet. It contains no water, no hydroxide, no oxygen and is perfect for things like Metalarc lamps. We seal it in glass ampoules under dry argon or helium. 4 While we were at it, we decided to turn it out in handier form. Here you see an enlarged view of mercuric iodide beebees that are actually about the size of fine sand. Note their uniformity.
Iodide caviar. We went on to make other superpure, superanhy drous iodides such as mercuric iodide and lithium iodide. 16 C&EN APRIL 19, 1971
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ν < SYLVANIA FROM
(In fact, we are hotly pursuing all alkali metal iodides.) So now if you need a pure salt for a lamp or a molten solvent system, we have something extra good. Melting points are as follows: NaI-6SloC,HgI2-2S7oC,LiI-4S0oC. Other possible uses: solid state scintillation counters, infrared transmitting materials, molten salt heat-trans fer fluids, electrolytes for high-temperature batteries. And a lot more we don't know about. But you probably do. Samples to those who sound like they need them. Litera ture to everybody else. Write.
The third excitement. Everyone knows you can get phosphors to glow by shining some kind of electromagnetic radiation at them, such as X-rays or ultraviolet light. Or you can bombard phosphors with electrons, as in TV picture tubes. The third way of exciting them isn't as well known—you can get certain phosphors to glow by putting them into an alternating current field. They go through one of those complicated solid-state energy-absorption dances and spit out surplus energy in the form of a mellow light. We make electroluminescent phosphors. A green one which consists of zinc sulphide with a cop per activator—ZnS:Cu. A blue one in which the amount of copper is reduced by half. A yellow one with an added pinch of manganese— ZnS:Cu,Mn. The whole concept of "lamp" takes on a new meaning with these phosphors. Now lamps can be made in large, flexible sheets so that walls may be papered with them. Electroluminescent lamps make lovely instrument pan els and clock faces and night lights. They last practically forever and never die abruptly. Their soft glow is easy on the eyes. We make EL phosphors. Another Sylvania outfit makes EL lamps. No matter which you use, you'll make us happy. For more information, write to Dave Lundy of our Mar keting Department. We9re always glad to talk to you about tungsten, molybdenum, phosphor and iodide chemistry. G TE Sylvania, Chemical and Metallurgical Division, Towanda,
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