Harmlessly drinking glass unintentionally

February 12, 2008 7:23 AM

How much of my GLASS do I drink when I drink a glass of water?

About how many fundamental particles make up a typical drinking glass, and about how many of them do I drink when I drink a glass of water?

I'm also curious what the figures are for plastic or ceramic.

I have one ceramic cup, in particular, that I can taste every time I drink out of it. I'm assuming it's eroding like crazy.

posted by Eiwalker to science & nature (10 comments total)

Just a note, "fundamental particles" refer to quarks and whatnot.
posted by electroboy at 7:42 AM on February 12, 2008

Some chemicals are detectable at levels as low as 2 parts per billion (cite). For an 8 ounce glass of water, that'd be 0.45 micrograms. I couldn't even begin to speculate on the molecular weight of whatever you're tasting from your ceramic cup.
posted by 0xFCAF at 7:44 AM on February 12, 2008

According to FIJI, you should be happy that you're drinking that silica!
posted by fusinski at 7:49 AM on February 12, 2008

You can taste your ceramic cup in the liquid or from your mouth-to-cup contact point? How does it taste through a straw?

I wouldn't use that cup for food. There's a (very, very) small danger of lead in some ceramic glazes, depending up when your cup was made and where it's from. Put some plastic flowers in it and put it on a shelf. Buy a new cup.
posted by unixrat at 7:54 AM on February 12, 2008

Probably less glass than you would breathe in a few minutes from glass dust on roadways, etc. Not to mention rubber, salt, dirt, poop...

Read The Secret Life of Dust. Every day you're breathing dust from Amsterdam bicycle tires, Sahara sand, Stuttgart automobile factories, and so on.
posted by weapons-grade pandemonium at 9:03 AM on February 12, 2008 [1 favorite]

Because you can taste something does not mean you're ingesting it. You can taste a stainless steel spoon because the molecules fit the receptors on your tongue. It doesn't mean they fall off in your mouth.
posted by weapons-grade pandemonium at 9:07 AM on February 12, 2008 [5 favorites]

Reticulated water supplies generally contain silica - silicon dioxide, or "glass" - in concentrations ranging from a few ppm to 100's of ppm. It occurs naturally in water as a suspended / colloidial solid due to erosion, from the skeletons of diatoms and the like, is sometimes added to settle other suspended solids out, and forms the basis of most water filtration processes e.g. sand bed or DE filtering.

You ingest several orders of magnitude more glass (or almost anything else you care to name, for that matter) direct from the drinking water than you do from the glass.
posted by Pinback at 3:23 PM on February 12, 2008

The solubility of glass (silicon dioxide) in water is about 120 ppm, according to this material safety data sheet. Note that this is for a powdered form of food-grade silica; powders dissolve more quickly than big chunks of solids because of the increased surface-to-volume ratio. (That's why small-grained sugar dissolves more quickly in your tea than large crystals of sugar.) However, if you wait ~infinitely long, until you reach equilibrium, the final concentration in solution will be the same whether it started as a powder or a big chunk (like your drinking glass).

ppm = parts per million, by weight. Therefore, in a million grams of water you could dissolve 120 grams of silicon dioxide. Assuming your glass holds 8 fluid ounces, that's 0.237 liters of water or 237 grams of water. This means that, after waiting till the end of the universe to get to chemical equilibrium (keep that drinking glass covered so the water doesn't evaporate!), you will have dissolved 0.028 grams or 28 milligrams of silicon dioxide into the water.

I'm making a big deal about time here because one thing the solubility limit doesn't tell you is how fast something goes into solution. Glass just doesn't dissolve very fast, even that powdered food-grade silica. So the amount of glass that would dissolve into your water during the time it takes you to eat dinner will be negligible. By that, I mean it would probably not be detectable by any assay known today (although that's speculation - I don't do that kind of analytical chemistry).

To answer your question about how many atoms (not fundamental particles, as electroboy pointed out) your drinking glass contains, I just weighed one of my drinking glasses that holds about 8 fluid ounces of water. It weighed about 200 grams. The formula weight of silicon dioxide is 60.1 grams per mole, where a mole is the number of atoms or molecules in an amount of material equal to its molecular weight (sounds like a circular definition; it's not but I don't want to get into that now. The magic number here is that one mole of any substance contains 6.02 x 10^23 molecules of that substance.)

Following the definition, one mole of silicon dioxide is 60.1 grams, which will contain 6.02 x 10^23 molecules of silicon dioxide. My drinking glass that weighs 200 grams contains 200/60.1 = 3.33 moles of silicon dioxide, or 3.33 x 6.02 x 10^23 molecules. A grand total of 2 x 10^24 molecules of silicon dioxide. I don't know what you plan to do with that number, but it's fun. (By the way, 6.02 x 10^23 is also called "Avogadro's number", which is a great piece of geekery to lay on your friends - "Man, I was squashed into the subway with an Avogadro number of people this evening!")

Now that ceramic cup whose glaze you can taste? That's a little scary. Quite a few minerals are used in glazes and I'd bet that some of them are more soluble than silicon dioxide. More toxic too. I'd use that cup to hold pencils and get yourself a nice glass for drinking out of. There's a reason laboratory glassware is made out of glass - it's very inert, insoluble, low-leaching, and easy to clean. Good properties for both the lab and the kitchen!
posted by Quietgal at 8:20 PM on February 12, 2008

Just a note, "fundamental particles" refer to quarks and whatnot.

Right -- that is what I'm asking about. So far, nobody has proposed an answer to that question. Does everyone assume I'm asking about molecules, elements, or atoms?

Now, I don't even believe that anyone knows for sure how many fundamental particles there are in, say, 2 x 10^24 molecules of silicon dioxide; I just want to know what some of the contemporary physical theories say.

If you can tell me about how many fundamental particles there are in, say, a single molecule of silicon dioxide, then we'll just multiply that by 2 x 10^24 (thanks, Quietgal) and be done. Or, if different theories give different answers, what are they?
posted by Eiwalker at 9:55 PM on February 12, 2008

For the purposes of this calculation, you can assume glass to be silicon dioxide, SiO2. Silicon has an atomic number of 14 and an atomic weight of 28 (or close enough for this). That means there are 14 protons and 14 neutrons in a Si nucleus. Each neutron or proton consists of 3 quarks, giving a total of 28x3=84 quarks in a Si nucleus. Add in the electrons (equal to the atomic number, 14) and you get 98 fundamental particles in an average Si atom. The same calculation on Oxygen (atomic number 8, atomic mass 16), gives 16x3+8=56 fundamental particles. But remember that you have two oxygens in your glass molecule, therefore in total a molecule of SiO2will have 84+56+56=196 fundamental particles. Multiply this by Quietgal's result and you get 4 x 10^26 fundamental particles in your glass (more or less).

How many of them do you drink each time? Well, as a rough estimate, you could try thinking of it in terms of how many times can you use the glass before it dissolves into nothing. Quietgal's data sets a lower limit of 200/0.028=7143 times, assuming that you leave the water in the glass for a very long time each time before drinking. Therefore, you drink a maximum of ~ 5.7 x 10^22 each time (4e26/7000). In reality, the actual use limit of the glass will be several orders of magnitude higher than the theoretical minimum. 5 orders more at least, I'd guess, which would give number of around 5x10^17.

Of course, all of this is according to the Standard Model (wp) of particle physics, which is the most commonly accepted explanation at the moment. The linked article contains some pointers to alternative theories.
posted by Jakey at 5:50 AM on February 13, 2008 [1 favorite]