Searching for short stories published in 1938 has been a bit of a chore for me, as several of those stories have never been reprinted. For the rest, let me say thank goodness for Interlibrary Loan. So it's always great when you can find stories for free on an online resource. Charles Tanner was part of the convention committe (in fact, he was the chairman) for the 7th World Science Fiction Convention (in Cincinnati, Ohio) held in 1949, and while his fiction output was not great, he did publish 16 short stories between 1930 and 1951. His grandson, Jeff Tanner, has made Charles Tanner's narrative works available for free on the Internet, with accompanying cover art and interior illustrations. "The Vanishing Diamonds" appeared in the June 1938 issue of Amazing Stories and is a good example of a short story that could also be used to teach basic concepts in chemistry.