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?. 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? 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 -- 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]>
