Pavel Hochmut wrote: > As to the content of the stomach: I apologize, that sulphuric acid in the > stomach was maybe some trash. I shall see what happenes in the stomach > exactly. > But: I still consider the silver to be pretty reactive: > 1. When you leave it on the air, it turns black within some days. It´s the > matter of the hydrogen sulphide content in the air and silver sulphide > appears on the silver surfaces.
That is true, the one thing that silver reacts with quite easily is hydrogen sulfide. This is well known and is what produces silver tarnish. > > This, maybe is also answer to that, why sometimes the electrodes turn dark > during the batch process. That is a reaction between hydrogen and oxygen ions and silver, hydrogen and oxygen ions are extremely reactive. > I suppose, that dissolved gasses in the DW can > react with the electrode surface. There is only one dissolved gas that I know of that will react with silver, and that is hydrogen sulfide. > > As I was informed, the best way to get out the gasses from the DW is to boil > it shortly before starting the batch. > Can I ask somebody who faces this problem with the electrodes colour change > to try this if it works ?????????????? Water is made up of 100% gases, two parts hydrogen and one part oxygen. During electrolysis they are split up, and one goes to the anode and the other to the cathode. Both are extremely reactive, and can produce silver compounds. The oxygen ions will likely produce silver peroxide, which is black, and the hydrogen ions will likely produce silver hydroxide, which spontaneously reduces to silver oxide, which is more of a brown color. > > 2. Ocassionaly I work with plated silver material and if even I touch it > with my hand, an exact fingerprint turns dark in several minutes on the > silver surface. Silver is reactive with sulfur. The organic sulfur compounds on your finger are tarnishing the silver. This is the one of the few elements that silver has a real attraction for. > So, I must handle it wearing gloves. There are some > chemicals in the sweat, that silver reacts with almost instantly. It seems, > as if it is developed photographic image of my fingerprints. > 3. As to the reactions with the acids, as below: It is true, there is no > reaction with the hydrochloric acid. > If you pour sulphuric acid over silver plate, there is but a slight > reaction, where the silver sulphate appears covering the whole surface and > as it is not soluble, it makes passivating (= insulating) layer over the > silver. Thus the more reaction is suppressed, the silver surface is > "passivated". In case of CS might the situation be quite different... Silver is more electronegative than hydrogen, so although silver likes sulfur, the hydrogen in the acid likes it more. No reaction should be expected, but silver will dissolve in concentrated sulfuric acid. > > As to the fuming nitric, the silver dissolves absolutely in violent > reaction, with the sulphur nitrate resulting from this reaction. Try it with colloidal silver. I have, and found that the silver is untouched by the nitric acid as evidenced by an unchanged tyndall. If it did react then it would produce silver nitrate, not sulfur nitrate. If you try it with a piece of silver, you have to use pure silver. Nitric acid can attack silver alloys such as 14 carat silver violently. The other metals set up a battery type of reaction, where the silver pulled out of the alloy by the current as silver ions as the acid reacts with the copper, and silver ions will react with the nitric acid. Even .999 silver will do this slowly, so at least .9999 should be used to do this test. Silver will dissolve in concentrated nitric acid, but that is different than reacting with it. > > I have asked for the above information my friend - he´s chemist. > So the answer to the Peter´ s question is: It was fuming nitric what > violated your silver chain. Once again I doubt you had a silver chain, I don't even think they make them. Silver is way too soft to make a chain that will not fall apart. Most likely it was 14 carat silver, which WILL react with acids as per the above information. However, if the acid is a strong nitric or sulfuric, then pure silver can dissolve in it. See: http://www.madsci.org/posts/archives/mar98/889541118.Ch.r.html Copper and silver are fairly unreactive metals, that do not react with ordinary acids, and do not readily react with oxygen. Both metals retain a fairly high polish, with no tarnishing, in many environments. But keep them out of the kitchen! Both copper and silver tarnish very readily in the presence of sulfur, or certain sulfur compounds. In the presence of rotten egg gas (hydrogen sulfide), or certain organic sulfur compounds, or even yellow elemental sulfur, copper and silver surfaces readily react to form black layers of copper or silver sulfide. These layers are very hard and insoluble; they are also rather unsightly! Cooking eggs is a notorious source of sulfur compounds that tarnish silver; so are natural gas or town gas fires. According to http://www.webelements.com/webelements/elements/text/Ag/chem.html Silver dissolves in sulfuric and nitric acids, but does not react with them. Silver and gold are called noble metals because of their inert nature. The reactivity of metals is in the following order: potassium sodium calcium magnesium aluminum zinc iron lead copper mercury silver platinum gold As you can see, only platinum and gold are less reactive than silver. http://homepages.westminster.org.uk/nick.hinze/Notes/Lower%20Shell/metals.htm One general idea is that the more reactive a metal, the greater its tendency to react and form compounds. This is why metals above copper in reactivity are rarely found native, whereas gold and silver are often found in their natural, uncombined state. Some unreactive metals, like gold, silver and copper can be found uncombined in the earth. However most metals are found combined with other elements in compounds known as minerals (e.g. metal oxides and sulfides). Rocks containing these minerals are called ores. Ores are the raw materials for making metals. Extremely unreactive metals such as silver, gold and platinum are often found native (uncombined) in underground deposits. No chemical method of extraction is therefore required in such cases. Also see: http://www.learn.co.uk/default.asp?WCI=Unit&WCU=35698 http://www.sciencenet.org.uk/database/chem/industrial/c00109b.html http://www.wolds-silver.freeuk.com/silver_properties.htm Chemically, silver metal is not very active. It is insoluble in dilute acids and alkalis, but it does dissolve in concentrated nitric or sulfuric acid. It does not react to any great extent with oxygen or water at ordinary temperatures. However, sulfur and sulfides readily attack silver, to cause tarnishing through the formation of a surface layer of water insoluble black silver sulfide (Ag2S) . This explains why eggs, which contain sulfur (in the proteins), are efficient tarnishes of silver. Tarnishing is also slowly produced by the small amounts of hydrogen sulfide (H2S) present in the atmosphere. So although silver will dissolve in concentrated nitric or sulfuric acids, it does not react with them. This tends to support all my experiments where I was trying to react silver with something so I could test for it at room temperature and was unsuccessful. The only thing I was able to get to work was mixing with a fuming acid, and boiling dry. Apparently it dissolves in the acid, then when boiling dry the hydrogen is driven off leaving the nitrate or sulfate radical behind, and it will then react with the silver since the hydrogen is now not available to compete with it. Marshall > > Pavel H. > > Marshall Wrote > > silver is one of the most inert metals there is, it is slightly more > reactive than gold, but > not much. You can drop it into fuming nitric, sulfuric and hydrochloric > acids > (independently) and nothing happens. > > Marshal: > > As a child once I try to clean a silver chain in an Ounce of the acid > tinners use to solder. The chain completely dissolved after a few minutes. > > What kind of acid do You think it was? > > Peter R > > -- > The Silver List is a moderated forum for discussing Colloidal Silver. > > Instructions for unsubscribing are posted at: http://silverlist.org > > To post, address your message to: [email protected] > Silver List archive: http://escribe.com/health/thesilverlist/index.html > > Address Off-Topic messages to: [email protected] > OT Archive: http://escribe.com/health/silverofftopiclist/index.html > > List maintainer: Mike Devour <[email protected]>
