"Between the electric light and the photo-electric cell is placed a glass vessel holding an alkali that is to be neutralized. Above is a tube from which an acid passes, drop by drop, through an automatic valve, into the alkali. A small amount of chemical indicator added to the alkali maintains a red color in it until it is neutralized. When a sufficient amount of the acid has dropped into the alkali, the red color disappears, indicating complete neutralization.
"When the solution is colored red, an insufficient amount of lights gets through to the photo-electric cell. As the red color gradually diminishes, the amount of light passing through increases, and when the solution is entirely clear the light reaches a critical value which causes the photo-electric cell to pass a signal to the radio tube. This tube operates the relay which closes a valve and shuts off the supply of acid.
"Using a device of this sort to perform such operations around a laboratory will save a great deal of a chemist's time. Its electric eye is about 165 times as sensitive to differences in color as any human eye."
[Sidenote: The tale of a golden atom--an astounding adventure in size.]
[Illustration: The fly landed with a thud on the center table.]
It was shortly after noon of December 31, 1960, when the series of weird and startling events began which took me into the tiny world of an atom of gold, beyond the vanishing point, beyond the range of even the highest-powered electric-microscope. My name is George Randolph. I was, that momentous afternoon, assistant chemist for the Ajax International Dye Company, with main offices in New York City.
It was twelve-twenty when the local exchange call-sorter announced Alan's connection from Quebec.
"You, George? Look here, we've got to have you up here at once. Chateau Frontenac, Quebec. Will you come?"
I could see his face imaged in the little mirror on my desk; the anxiety, tenseness in his voice, was duplicated in his expression.
"You must, George. Babs and I need you. See here--"
He tried at first to make it sound like an invitation for a New Year's Eve holiday. But I knew it was not that. Alan and Barbara Kent were my best friends. They were twins, eighteen years old. I felt that Alan would always be my best friend; but for Babs my hopes, longings, went far deeper, though as yet I had never brought myself to the point of telling her so.