Ok, at this stage in the game, I am completely convinced that this stuff is not safe. Let me explain my test results.
First, I would like to go back over the chemical tests done that were pulled from another site. I admit, I did not go over them carefully (was not in a chemistry mind set) the first time, nor did I dispute what was said about them. The truth is, they are more revealing to me now (assuming, again, that I have done the appropriate calculations) then they were before.
First, let me give you some chemical equations.
1) CaCO3 <--aq--> Ca(2+) + CO3(2-) Ksp = approx. 5 x 10-9 (VERY little)
2) CO3(2-) + H+ <-----> HCO3(-)
3) HCO3(-) + H+ <-----> H2CO3 -----> H2O + CO2
Basically, the reason CaCO3 can dissolve at all is because it has the capacity to accept a proton to become bicarbonate (in solution). Pure water has very hew protons, so VERY little solvation will occur. The things to keep in mind: When a chemical on one half of the equation is increased, it will push the equilibrium the other way. (example, if you took eq. 2 and added HCO3(-) then it would push the equilibrium more towards CO3(2-) and H+ (causeing an increase in acidity and CO3(2-) concentrations).
Let me break something down. In the test, a portion of calci-sand was dissolved in 2M HCl. In that test, it took 4 days in order to dissolve 20% of a 1 gram sample of CaCO3. Let me bring that into terms everyone can (hopefully) understand.
1 Mole of CaCO3 weighs 100 grams.
1 gram was used, therefor there were 0.01 moles involved in the experiment.
2M HCl means there is 2 moles/ liter. 10 ml were used, therefor there was 0.02 moles of HCl in the experiment. Basically, there was double the amount of HCl as there was CaCO3. In this experiment, STILL only 20% dissolved. Given enough time, I am confident more of the CaCO3 would have been dissolved (Basically, HCl dissolves compeltely, so there were 0.02 moles of H+ to drive hte reaction forward. Because the end of the reaction is CO2 which can leave the reaction (bubble out) it will only come to a stop when Pressure of CO2 in the atmosphere balances out the CO2 in solution, after the pressure from the H+ is dissipated, anyway, that was not important).
If there had been even amounts of HCl and CaCO3 in the solution (as there was in another reaction) most of the CaCO3 would have remained in an undisolved state due to only 1 H+ being availible per CO3- (when the solution is saturated with HCO3-, some of the H+ must go to rxn 3, which is 2 H+ per CaCO3, which would leave alot of it undissolved).
Now, lets take a look at a dragons stomach. It has been stated on this thread that the pH of a dragons stomach is 3. if this is hte case, that means it is 0.01M HCl. Assuming that the dragons stomach is actually 3 ounces (about 100ml) large (I think it is less, but it doesn't matter) that would make 0.001 moles of HCl availible in order to help with solvation. This means that, even if you assumed that a 2/1 ratio would dissolve EVERYTHING (given enough time (weeks) it may) the most CaCO3 your dragon could eat would be: 0.0005 moles of CaCO3. Fine (you say) but how much is that really? since 1 mole is 100 grams, multiply by 100 and you get... 0.05 grams. For a point of reference, 1/4 of a teaspoon is 1.5 grams.
Basically, CaCO3 is hardly a "soluble" substrate right now. But wait! there's more!
As well as doing some of the calculations from the other test, I also went and got some CaCO3 (forget name brand, but it is calci-sandish stuff) of my own to do some tests.
1) I tried to disolved 1.5 grams (1/4 of a teaspoon) in 1L of regular water. So far in 12 hours, no noticable amount has disolved.
2) I tried to disolve the same amount in vinegar. Again, little has been disolved thus far, but you do see some bubbles comming up (see equations above, the final step is converstion to CO2). So, the vinegar may dissolve some, but it will take a long time.
3) Just for fun, I simulated what would happen upon entry to the intestines. In the intestines, duodenum releases a concentrated HCO3- mixture to neutralize the stomach acid. When I dissolved baking soda (NaHCO3) in water, saterated it, and added it to a saturated solution of CaCO3 (saturating CaCO3 is easy, as so little dissolves) guess what happened? Yep, precipitate. If you look at the equations above, you will see that if you add HCO3- to the mixure, it will push equation 2 to the left, which will push equation 1 to the left, which will give us a nice solid. When I added an acidic (acetic acid) saturated solution of CaCO3 to the baking soda mixture, the same thing happened (after alot of bubbles in order to neutralize the vinegar).
So, basically, my results are not good for me. Another thing that I had actually read about CaCO3 was that it was different in that the solubility would go DOWN with increasing temperatures. Basically, if you mixed a solution of CaCO3 at room temp, saturated it, and heated it, you would get a precipitate. I tried to duplicate this, but due to such a low solubility, I have not yet been able to prove it.
Take this whole thing as you will, I will be continuing to play with my calci sand (might even call the company to get a refund for their "soluble" product).
Steve
