----- Original Message ----- From: <[email protected]>
> In a message dated 3/25/01 4:21:53 AM EST, [email protected] writes: > > << Subj: Re: CS>Re: saturated solution > Date: 3/25/01 4:21:53 AM EST > From: [email protected] (Ivan Anderson) > Reply-to: [email protected] > To: [email protected] > > Frank, > > I am a bit confused. > > I do not see why anions are required at all for silver ions to go into > solution. The ions will be solvated, surrounded by water molecules. If > there are no anions, there will be nothing for the silver to complex > with and so the saturation point will depend upon the interaction > between the ions themselves. > > There is 10^-7mol/L OH- ions in water at pH 7, which will allow Ag+ ions > to reach a concentration of 0.15mol/L which is about 16.2g/L or 16.2ppt, > given that the solubility constant of AgOH is 1.5 x 10^-8 > > The solubility constant of Ag2Co3 is 6.2 x 10^-12 which gives a > concentration of 2.32 x 10^-4 mol/L of Ag+ which is about 25mg/L. > In any event CO2 will dissolve in water to a concentration of about > 10^-5M and result in a pH of 6.3 > > Ivan: Is your figure 10-5 mol/L solubility of CO2 in water for 1 atm pressure > of CO2, or for air which has, I believe, 0.03 atm partial pressure CO2?. Yes. > However the CO2 exists primarily as a hydrated species, of which about 0.1% > reacts to form H2CO3. > > Ivan: Couldn't that figure (0.1%) be altered by the presence of other species > that could form complex molecules encorporating CO2 in their matrix? Probably but that would require a 1000:1 change in CO2 concentration. > change This gives us about 10^-8M of CO3, which gives about 2.4 x 10^-2M of > Ag+ (2.5g/L). > > So it is not the concentration of the anions which limit the solubility > of silver at far greater than normal CS levels. How do you explain the > 13.3ppm limit? > > Ivan: As I recall, calculations to determine the solubility of (for example) > silver in an aqueous medium containing multiple ionic species must be done by > seeking the SIMULTANEOUS algebraic solution from solubility product data > which account for ALL species present. What you have done is to treat each > solubility product calculation separately. This shortcut MAY turn out to be > an approximation to the actual silver solubility values, BUT how could we > have an a priori knowledge of such a possibility? The long way is the best > way to provide an accurate estimate of silver solubility. The only > assumptions inherent in such a calculation would be that (1) species > concentrations are dilute (Dilute solutions are required to avoid first and > second order interactions which could effect their respective activity > coefficients. In other words, the assumption that concentration equals > activity would NOT be valid. However, we are in very good shape here.), (2) > that all species are in, if fact, present, and in equilibrium. Anyway, with > your computer finesse, I wouldn't be surprised if you had an algorithm or two > waiting in the wings ready to expedite such a calculation. Roger No, unfortunately I have to do it all by hand. I am about to study solubility and activity formally in my analytical chemistry paper, so I will wait until then, and until I read Frank's corrections. Ivan --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.240 / Virus Database: 116 - Release Date: 23/03/2001 -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: [email protected] -or- [email protected] with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: [email protected] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>
