Of all the things my brother and I had to clear out of our parents’ house after my mother died, probably the most dangerous was a dark, scabby-looking lump almost covered with a clear liquid in a pint Mason jar. The dark lump was around one and a half times the volume of a golf ball. The lump was solid, metallic sodium. The clear liquid was mineral oil, which is intended to prevent exposure of the sodium to the air.
Despite the fact that sodium is the sixth most common element on Earth, it is never found as a pure element (metallic sodium) in nature because it is very reactive with water. It’s so reactive that it will strip off a hydrogen atom from a water molecule and attach itself to the remaining oxygen and hydrogen, forming sodium hydroxide. In the process it releases heat and a free hydrogen atom. Hydrogen can react in the presence of oxygen and heat, so the sodium-water reaction can be dangerous.
My father got this lump of sodium sometime in the distant past, maybe even before I was born. He stored it and other odd chemicals under the house we lived in. When my brother and I were kids, he would occasionally take the sodium out, cut off a small piece, toss it into the grass and sprinkle water over it. The sodium would hiss, smoke, burn, and sometimes pop as the hydrogen ignited. After we moved from our original house, my father stored it in a metal Post Office storage box. I don’t think he even touched it after he put it in that box, so it was left for us to dispose of.
I had kept the jar in a cooler cushioned with a pillow for the last couple of years. The chemistry department at Berry College in Rome offered to have their hazardous waste disposal company remove it, but the cost would be $275. I looked into the recommended methods for disposal, which involve a vent hood and repeated exposure of the sodium to various alcohols until the sodium has fully reacted. At that point, the remaining solution can be dumped down a sanitary drain. However, even chemists can make mistakes.
The recommended procedure seemed to be beyond my capability, so I decided to take the simple and crude way out. I took a wheelbarrow, five gallons of water and a Mason jar of sodium up to the site of our new house. This process can be dramatic, not to mention dangerous.
I was a little surprised that the jar opened so easily, but I guess I should have expected it, since it was well lubricated with mineral oil. I dumped the sodium and mineral oil into a plastic bowl.
Excuse the poor focus. I was using one hand for my phone and the other to manipulate the sodium.
The dark look of the lump is a coating of partially reacted sodium on the surface. Even though the lump had been partially submerged in mineral oil, there was enough water vapor that was either in the jar or that leaked slowly in that the surface reacted.
Metallic sodium is a soft metal that is easily cut with a knife. The unreacted metal is a bright silver. Here is what it looked like when I cut it. It’s actually quite pretty.
I was using a regular Swiss Army knife and wearing thick household gloves. It’s not a smart idea to touch metallic sodium with your bare hands because of the moisture on the surface of the skin. I cut the sodium into pieces a little smaller than a grain of rice. When I was careful to manage the size and number of pieces I put into the water, the sodium formed a small, smoke-filled bubble that zoomed around the surface of the water.
You can see a few smallish bubbles here. Perhaps surprisingly, sodium, although a metal, is actually lighter than water, so it floats.
If I cut a piece a little too large or got too many pieces together, they produced a flame. A few times they exploded and sent pieces of molten sodium through the air followed by trails of smoke. Unfortunately, I couldn’t do my work and take pictures of sodium explosions at the same time.
The sodium hydroxide that the reaction produces is known as lye or caustic soda, so after I finished reacting the sodium I was left with lye solution and maybe a few small pieces of sodium on the ground. I dumped the lye solution; I’m not worried about that since rain will dilute it and it will end up buried under our driveway anyway.
I’m also not worried about the small pieces of sodium that popped out of the wheelbarrow. Sodium is so reactive with water that even the water vapor in the atmosphere is sufficient to take care of that. When I initially cut the sodium, it had a shiny surface, but that shiny surface began to turn dull within a few minutes of exposure to the air. The small pieces that I cut also began to react immediately. I felt the heat of the reaction in the palm of my hand through my glove as I carried the pieces the few steps from my cutting board to the water. At one point I noticed a small mass of bubbles, maybe the size of the tip of your little finger, next to the cutting board. I apparently had brushed a very small piece of sodium off the board and onto the bed of the Mule I was using to hold the cutting board. That little piece of sodium was reacting to atmospheric water vapor and was busy fizzing away. I’m confident that any small pieces of sodium that I left around the site had fully reacted within hours at the most after I left. In fact, they were probably all gone by the time I left.
I had no idea that metallic sodium is still available, but I found a vendor on Amazon. You can buy one pound for $185. I recommend that you not do so.
In organic chemistry lab when I was an undergraduate, we used a tiny piece of metallic sodium as part of a reaction. The metal reacted in the reaction flask exactly as you described.
After what I (incorrectly) deemed enough time for the reaction to have finished, I drew off the supernatant and then dumped the remaining ingredients into the laboratory sink. I don’t know if you took organic chemistry, Mark, but organic chemistry lab uses acetone a lot to rinse out reaction vessels, and the acetone is flushed into the sink.
Well, you can imagine what happened. The remaining tiny piece of sodium reacted with the water in the sink, set the hydrogen on fire, and that, in turn, caused the acetone to catch fire. It was scary, but completely confined to the sink, thank goodness. The poor Teaching Assistant almost went crazy with the fire extinguisher. (To add insult to injury, I got a really lousy grade on that lab because my reaction didn’t create a satisfactory amount of the desired reaction product.)
My dad once brought home a baby food jar with a rather significant amount of mercury sloshing around in it. I dropped the jar and mercury went everywhere. The house in which this occurred is probably still contaminated.
I have to confess I never took a chemistry class in my life. I managed to fulfill my science requirements with biology. This post is very interesting, but I lack the proper education to make any sense of it.
Scott — Ah, yes, mercury. We had some of that, too. When we were kids and people didn’t realize how dangerous mercury is, we would take a little mercury and spread it around on a penny to make it look shiny.
Robin — I’m not a chemist by any stretch, but the longer I go the more interesting everything gets, including chemistry. The main thing to know about metallic sodium is that it makes a wonderfully fiery and loud display if you put enough of it into water, and don’t let it touch you.
I also wanted to mention that I have tried to comment on your blog but seem to be having some problems. Sometimes I can, and sometimes I can’t. I particularly wanted to comment on the post about letters, because I found a letter from my father dated in 1977 when I was living at Lake Tahoe. I reread it occasionally because I can hear my father’s voice when I do.