Early History 



Vonnegut joined the staff of the Research Laboratory in the Fall of 

 1945 and he continued his supercooling investigations there. 



SUPERCOOLING OF METALS 



In various contacts with Langmuir and Schaefer, Vonnegut learned of 

 the work they were doing. Knowing that Schaefer was already working on the 

 supercooling of water, he switched his activity to the supercooling of metals, 

 in order to avoid duplication. He found he could supercool Woods metal by 

 subdividing it into many small, independent particles, and he developed a 

 technique of studying the effect with x-rays. He also -worked with tin. (62) 



NUCLEATION STUDIES 



Vonnegut had been interested in the work being done by Langmuir and 

 Schaefer and had kept in rather close touch with it. In the fall of 1946, Lang- 

 muir asked him if he would be interested in helping with the quantitative work 

 being done on the number of ice crystals produced by dry ice. As a result, 

 Vonnegut applied himself to this and other problems in the general study of 

 nucleation. 



SILVER IODIDE 



It occurred to Vonnegut that some substance very similar to ice in its 

 crystal structure might serve as the nucleus for the formation of ice crystals 

 in the cold box. He went through all the known tables of crystal structure and, 

 from over a thousand compounds, selected three substances that he thought 

 might have possibilities: lead iodide, antimony and silver iodide. (56) 



He dropped samples of each of these three substances into Schaefer ? s 

 cold box. The results were almost negligible, although he produced enough 

 effect with the lead iodide to warrant further experiment. He and Schaefer 

 tried iodoform and iodine and obtained ice crystals in small numbers with 

 them, too, but nowhere near as many as with dry ice seeding. 



The problem intrigued Vonnegut. He decided to try a metal smoke in- 

 stead of the powder. He introduced some silver smoke into the box by draw- 

 ing an electric spark from a piece of silver, and it produced in the cold box 

 a swarm of ice crystals. 



The results were so spectacular that he decided to try silver iodide 

 again, but this time as a smoke, for the effect with silver did not persist. 

 First he vaporized silver iodide and then he introduced into the cold box 

 the smoke resulting from the rapid condensation of this vapor. It was a com- 

 plete success. Further investigation showed that his earlier negative results 



