Chemistry Solutions

© bigstockphoto.com/Edward Stephens

I have always had a fondness for studying nuclear chemistry. As a freshman chemistry major, it sometimes felt like the only subject I seemed to be good at! That’s why, when I began teaching high school chemistry, I was very disappointed that only a handful of days were devoted to nuclear chemistry on the pacing guide.

I still teach it with voracious fervor, as if it were the only topic that matters, and I often look for ways to bring more of it into my classroom. In my years of teaching, I’ve found that the real-world applications of nuclear energy have been easy for my students to understand. We discuss power plants, atomic bombs, and medical applications; through these Socratic seminars, we are understanding and saving the world!

Hook, line, and safety

One way that I have found to make nuclear chemistry a little more real is to allow students to observe radioactivity up close by measuring it with a Geiger counter. Several antique materials were produced before the dangers of radiation were understood. I’ve found uranium glass (figure 1), which can often be found in antique stores, to be a safe and interesting material for students to explore, as the radiation levels, though often detectable, are still lower than most natural background radiation. (Note that the terms “Vaseline glass” and “uranium glass” are often used interchangeably, as glass containing uranium has a slight greenish color in natural light that resembles Vaseline.)

Student safety should be prioritized when handling radioactive materials. The choice to use a Geiger counter as a measuring tool, rather than a dosimeter, depends on what you’re measuring. A Geiger counter measures real-time presence and intensity of radiation, picking up the frequency of alpha, beta, and gamma radiation being released. Dosimeters, on the other hand, measure the accumulated amount of radiation over time, which is a necessity for anyone who visits a radioactive environment on a regular basis. The Oak Ridge Associated Universities (ORAU) Museum of Radiation and Radioactivity is an excellent resource on the safety surrounding uranium-containing glass and glazes. On the whole, these antiques are accepted as safe to handle, as the accumulated dose over a short period of time is less than that of background radiation.^1,2 

What is uranium glass?

Glass manufacturers began to color glass with uranium oxide compounds after observing that these compounds produced a fluorescent effect. This practice gained popularity in the 1830s and reached its height of popularity between the 1880s and the 1920s, when several different uranium glass classifications emerged based on the overall color and type of glow emitted under ultraviolet light. The government halted the use of uranium compounds in glass production from 1943 until about 1958 due to governmental interest, first for experimental uses and later for stockpiling the compounds for defense and military purposes.³  Uranium glass produced prior to 1943 contained from 2 to 25% natural radioactive uranium (by weight)¹ , while after 1943 only depleted uranium was used, and typically in lower concentration.

Figure 1. Uranium glass under black light.

Natural uranium is composed of several isotopes. Uranium-238 is the most abundant, making up 99.27% of natural uranium. The next-most abundant isotope is uranium-235, which comprises 0.72% of a natural sample. A few other isotopes are also present in trace amounts. Both ²³⁸U and ²³⁵U are radioactive, with half-lives in the millions of years. The lighter of the two, ²³⁵U, is fissionable and, thus, useful in nuclear weapons and nuclear energy production. Depleted uranium is the mix of isotopes that are present after samples have been processed to remove as much as possible of the ²³⁵U for use in these applications. Due to the differing daughter isotopes produced throughout the decay chains of each uranium isotope, the uranium that is depleted of ²³⁵U is also decreased in overall radioactivity.

Radioactivity as a phenomenon leads to some wonderful classroom connections that can help students gain a more authentic understanding of the nature of radioactive decay. Depending on the percentage of uranium used in the glass composition, some pieces will register radioactivity with a simple handheld Geiger counter. Therefore, I typically do not simply go antiquing for uranium glass; instead, I look for items that may be radioactive, based on how old they are.

Demonstrations with the Geiger counter have really captured students’ attention! Due to the use of natural uranium in the older uranium glass samples, they can register about 0.065 mR/h or 0.7 µSv/h, and can even set off a Geiger counter alarm given enough exposure. When students see the reading on the Geiger counter and hear the alarm sound, those numbers suddenly mean something.

For dramatic effect, I also use the Geiger counter on a 1920s “radioactive red” Fiestaware plate (figure 2) that I found at an antique store (2.1 mR/h or 20.8 µSv/h). To clarify, at a constant exposure rate of 0.065 mR/h, a student would need to be in contact with a piece of uranium glass for about 154 hours to receive the same exposure as one chest X-ray (10 mR). Similarly, at a constant exposure rate of 2.1 mR/h, a student would need to be in close contact with my Fiestaware plate for just under five hours to receive the same exposure as one chest X-ray.

Figure 2. Geiger counter measuring the radioactivity of a 1920s Fiestaware plate.

After observing a few positive Geiger counter readings, we discuss whether the samples are safe to eat or drink from, and whether they are even safe to handle at all. (Note that, though these antiques are not regulated substances, it is recommended that people not eat or drink from dishware containing uranium, and that chipped or broken pieces be disposed ofaccording to your local radiation control program, as radiation sources are more damaging if they are inside the body, due to more direct exposure to body tissues). I then have students hold the Geiger counter closer and farther away from the pieces to find how the level of detection fades with distance. Next, they try placing different materials between the Geiger counter and the object to observe the penetrating power of the radiation. Eventually, students can infer the type of radiation (limited to alpha, beta, and gamma radiation) being emitted based on how their experimental changes affect the level of clicking in the Geiger counter.

Radioactive? That’s not all!

While the radioactivity of uranium glass is what first captured my attention, another property soon stole the spotlight. Several years ago, a physics colleague and I were discussing various science-related topics, and my interest in nuclear chemistry came up. My colleague disappeared into his storage room, and brought out some marbles and a black light. Under the black light, the marbles began to glow a neon yellow color. My colleague explained that the glow was produced because the glass in the marbles contained uranium. I knew uranium was radioactive, but I hadn’t realized it was also fluorescent. This is what led me to research the background of uranium glass and to extend its use in my classroom with an additional content unit.

Uranium glass has become a bit of an internet sensation lately, particularly around Halloween. This is largely because it glows when exposed to low-wavelength black light. I have, over the years, become a collector of uranium glass, most often finding samples at antique stores. I now take my 365 nm black light flashlight on every antiquing adventure, keeping an eye out for the vibrant green glow.

When teaching my electrons unit, I bring out the uranium glass once again. As the uranium ions absorb the high-energy UV-A light, electrons are excited to higher energy levels. The glow is produced by the electrons in these ions releasing excess energy in the form of visible light. I demonstrate this phenomenon in my classroom after students have been exposed to concepts of atomic structure, isotopes, and electron configuration.

I like to begin with the question, “What makes it glow?” Students consider whether it is the radioactivity they previously learned about, or if something else is responsible for the glow. I again bring out the Fiestaware plate and let students hypothesize what would happen if a black light was shone on it. Like any good scientist, we decide to try it…and no glow. Students then explore different ages of uranium glass pieces with both the black light and the Geiger counter: there is a glow, but minimal radioactivity for many of the pieces.

Segue to the quantum model

At this point, I turn students’ attention to different materials: other types of antique glass (figure 3), as well as minerals that glow in black light. Glass containing selenium will glow a vibrant pink color and glass containing manganese will glow a neon orange. Amberina, glass containing cadmium, will also glow a yellow-orange color under black light.⁴  Next in our investigation, we bring back the Geiger counter to test the radioactivity of these types of glass, and discover there is no radioactivity. Students begin to deduce that it must be something about the black light itself that makes the glass glow. This conversation has proved to be a great way to introduce the quantum nature of atoms.

Finding ways to use the different phenomena that can be demonstrated using antique glass has reminded me that chemistry is not just formulas, reactions, and math. It is an opportunity for discovery and curiosity. Every time a student hears the Geiger counter click or sees the eerie glow, they get to experience what first attracted me to the topic: curiosity and wonder. A mild fascination with nuclear chemistry has turned into a tradition of exploration and inquiry-based learning in my classroom. From discussing isotopes and their uses to seeking out fluorescent glass in antique stores, the most important part of the lesson always remains the same: science is everywhere, and shines most brightly when we take the time to look a little closer and dig a little deeper.

References

¹Oak Ridge Associated Universities (ORAU) web page, “Vaseline and Uranium Glass (ca. 1930s).” https://orau.org/health-physics-museum/collection/consumer/glass/vaseline-uranium-glass.html (accessed Jan 7, 2026).

²ORAU web page, “Fiestaware (ca. 1930s).” https://www.orau.org/health-physics-museum/collection/consumer/ceramics/fiestaware.html (accessed Jan 7, 2026).

³Aurora Historical Society web page, “Collections spotlight: Uranium Glass.” https://aurorahistory.org/collections-spotlight-uranium-glass/ (accessed Jan 7, 2026).

⁴Barnes & Bridge web page, “Glowing Glass.” https://www.barnesandbridge.com/general-7 (accessed Jan 7, 2026).