Lead Acetate (Heavy metals can be sweet, too!)
25th May 2006
Lead is one of the most familiar heavy metals to people. Disquieting is the fact that so many people haven’t handled it because of all the concern about its toxicity. Fishing weights are increasingly being replaced with heavy but less-toxic alternatives, like bismuth.
If you’ve never handled lead, please try it. I worry that it will go the way of mercury and you just won’t be able to get it in ten years. I can get all sorts of weird stuff in a chemistry building, but you don’t really have that luxury. It is soft and magic. If you have it in bar form you can bend it like Superman. It will make your week. Just wash your hands afterwards, and don’t store it in the butter dish.
Enter one of my heroes, Theodore Gray, with his Periodic Table Table. His entry on lead does the element more justice than I will. He also notes a few places you can get lead: hardware stores, fishing stores, and Wal-Mart. With lead’s wide use in plumbing, it probably won’t go away as quickly as I claim (the symbol for lead, Pb, comes from the latin plumbum. as you might expect, this is where the word plumbing comes from).
Lead is a lot like mercury - toxic, but not so terrible. You can handle lead pretty freely - for instance, I’d hold lead in my hands, not mercury. You can dent it with your fingernail. It’s surprisngly heavy, but not as heavy as gold or tungsten. Like mercury, the soluble compounds are much worse. One is Lead (II) acetate:
Lead acetate is also known as “sugar of lead” because it tastes sweet. You might be shocked that we know what it tastes like, but tasting chemicals used to be an important part of characterization. One Nobel Laureate (quite literally - I don’t use the term jokingly) tastes lots of things he makes. Obviously this isn’t the smartest idea (and I don’t do it!!), but it’s less dangerous than you’d expect. I’ve been told that even tetrodotoxin was characterized as “tasteless” (see this patent, for example).
Lead compounds are toxic in a number of ways. In particular they seem to be neurotoxic. One possible mechanism of lead toxicity is that it seems to cleave tRNA prodigously. Metal ions can often work as acids locally - they are positively charged, and water molecules coordinate their dipoles to them (oxygens facing the cation), creating not-so-bad acids.
Michelle Francl (if you like this blog, you will love hers, please check it out) notes that workers using certain lead salts used to add dilute sulfuric acid to their drinking water (not so bad - sulfuric acid in and of itself is not that toxic, and it was much better than the alternative of eating some lead (II)). Lead sulfate is a very insoluble salt, so the vast majority of the lead was sequestered in a precipitate.
That’s all, have a good night!
May 26th, 2006 at 12:05 am
Ever since I saw the Periodic Table Table site, I’ve wanted to get my hands on a good-size lump of tungsten. Alas, all the eBay peeps outbid me by a C-note at least whenever some comes up.
I also want to try my hand at making bismuth hopper crystals, which looks like it would be easier (and cheaper).
In further PTT news, I recall him mentioning that one of his correspondents was tasting several chlorides (by analogy with good ol’ NaCl). He characterized cesium chloride as “horrible,” as I recall.
I wonder if someone will make an “anything without a nitrogen in it is probably safe” t-shirt.
May 26th, 2006 at 2:20 am
here.
A pain to sinter the stuff, though.
May 26th, 2006 at 2:21 am
What’s amazing is that 500g isn’t “a good-sized chunk.” This is ca. 25mL of the metal in volume (neglecting the bulk associated with all the dead space in powders). Tungsten is heeeeeeavy.
May 27th, 2006 at 12:26 am
Oh, I’m sure my Eisenhower-era oven can reach 3400 °C without too much trouble . . . ok, maybe not.
May 28th, 2006 at 2:05 pm
From Nature’s Building Blocks by John Emsley:
He goes on to mention how lead acetate would be added to port wine to improve taste (possibly causing the death of any number of notable people of past).
May 28th, 2006 at 3:46 pm
I am unfamiliar with how lead works on the gut, but I am guessing the active ingredient probably was the opium. All the opium alkaloids impair gut motility. The old treatment for diarrhea, paregoric, is actually just opium tincture plus camphor to make it unpalatable. It still was opium, though, so they took it off the market. Imodium/Loperamide, the current OTC remedy, is actually a non-CNS active opioid.
Also, opioid addicts often remark on the fact that they experience prolonged constipation when using, and intense diarrhea as part of withdrawal.
Neat book, I hadn’t heard of this one yet. Thanks.
May 28th, 2006 at 8:56 pm
I wonder what they are using to weight Pinewood Derby cars for the Cub Scouts these days - I recall chunks of lead in the garage for this purpose when my brothers were young.