Thanks for your input Guenter, Some things you state need to be clarified. Most colloids as far as I know are made from positive or negative ions. Colloids formed from uncharged particles tend to flocculate and precipitate rather quickly. These colloids however do not bind together tightly when they settle and can be redispersed by stirring (eg paint).
I have never heard of H+ or OH- being trapped in a colloid particle. Generally the particle is surrounded by a layer of neutralising polar water molecules (Stern Layer) which travels with the particle. In the electrolysis of silver Ag+ ions are formed at the anode, it is these that form the colloid. You write: > What does this mean for our CS? > With low voltage direct current (LVDC) we detach silver ions from the > silver rod connected to the (positive) anode. In our solution we have > then silver ions Ag+, H+ and OH-. But when the Ag+ travel through the > water, some of them recombine with the OH- and form neutral AgOH > molecules. There are very small amounts of H+ and OH- in water pH7. During CS generation (electrolysis) the H+ ions are attracted to the negative electrode and the OH- to the positive electrode which have a far higher potential than the silver ions. Then: >These molecules now lump together and include H+ ions. These > positively charged colloids repel each other and prevent the formation > of larger particles or even precipitation of the whole stuff. > The faster the colloids are formed the more H+ ions are included, the > stronger is the repulsion which leads to smaller colloids. Adding salts > to a colloidal solution means adding of foreign ions which are attached > to the colloids and disturb the repulsion. Precipitation will result. Why would neutral AgOH attract H+ ions? As the H+ ions are reduced at the cathode and escape the solution as hydrogen gas, it is likely that the longer the electrolysis proceeds the less the available H+ ions. I doubt if there is much AgOH if any. Also: > I think with LVDC we generate colloidal silver oxide which is formed > from the AgOH by chemical transformation. Silver oxide is very unstable and disassociates with mild heating. In order to create AgO from AgOH we need O- radicals which are very few and far between in pure water. > If one wants to generate metallic colloids one has to use a different > process: One has to evaporate metallic silver by sparking under water, > by evaporating silver with a energetic laser beam, by ultrasound etc. > These silver atoms, dispersed in water, also lump together, but > typically include OH- ions. Most of these methods produce silver ions I believe. Comments? Regards - Ivan ----- Original Message ----- From: Guenter Poelz <[email protected]> To: <[email protected]> Sent: Thursday, 16 September 1999 22:11 Subject: Re: CS>Solutions Colloids Ions...was CS information needed > Hello, > let me contribute with what I have learned in chemistry. Many things > have been stated already many times in this list. I will try to clarify > some statements: > > Ions and colloidal particles both are charged, but they are different. > > - Metallic ions are formed when one or more electrons are stripped from > the outer surface of the uncharged metallic atom. Such an ion is then > positively charged. (It is also possible, but much more difficult, to > attach an ion to a metallic atom to generate a negatively charged ion). > Ions are also often formed by breaking a molecule into two "radicals". > If the electrons are unevenly divided, one part (with too much > electrons) becomes a negative ion, the other one (with lacking > electrons) becomes a positive one. > Water is an excellent medium to penetrate into salt molecules and breaks > it into ions (kitchen-salt NaCl is broken into Na+ and Cl-; also water > itself H2O breaks into H+ and OH- ). > > - Colloidal particles are formed by uncharged atoms or molecules. In the > formation process they lump together, bound loosely e.g. by water > bridges, but can fasten the bonds by chemical activity. These giant > molecules are formed so quickly that H+ or OH- (depending on the kind of > colloid) are caught and also built into the loose structure and gives > the colloidal particle its charge. > > What does this mean for our CS? > With low voltage direct current (LVDC) we detach silver ions from the > silver rod connected to the (positive) anode. In our solution we have > then silver ions Ag+, H+ and OH-. But when the Ag+ travel through the > water, some of them recombine with the OH- and form neutral AgOH > molecules. These molecules now lump together and include H+ ions. These > positively charged colloids repel each other and prevent the formation > of larger particles or even precipitation of the whole stuff. > The faster the colloids are formed the more H+ ions are included, the > stronger is the repulsion which leads to smaller colloids. Adding salts > to a colloidal solution means adding of foreign ions which are attached > to the colloids and disturb the repulsion. Precipitation will result. > > I think with LVDC we generate colloidal silver oxide which is formed > from the AgOH by chemical transformation. > > If one wants to generate metallic colloids one has to use a different > process: One has to evaporate metallic silver by sparking under water, > by evaporating silver with a energetic laser beam, by ultrasound etc. > These silver atoms, dispersed in water, also lump together, but > typically include OH- ions. > > To improve the insulation of the colloids from each other, and not only > rely on the electric repulsion, some companies manage to cover the > colloids with a skin of organic compounds, e.g. proteins. > > To what group of colloids the HVDC or HVAC CS is belonging, I have no > idea. > > Hopefully this helps to clarify, > Günter > -- The silver-list is a moderated forum for discussion of colloidal silver. 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