Colloidal Silver Chemistry

Colloidal Silver is a popular home remedy for a host of ailments. It can be purchased at health food stores, and of course on the internet. It is expensive though considering a pennies worth of silver may cost $10.

For that reason, many people attempt to make it themselves through a simple process of electrolysis. The most common method is simply to put two silver wires into a glass of water and connect the wires to a couple of 9 volt batteries. There are two important variations in the process though, one very good, and one very bad.

So what do people actually make and call Colloidal Silver?

Well, that depends on the method they use. Here are the three main methods I hear of people using:

I) Distilled water + silver anode at room temperature.

In this method, free hydroxyl ions in the water initially react with the positive silver electrode to make silver hydroxide (AgOH). Silver hydroxide is unstable and rapidly decomposes to silver oxide Ag2O. If you remember your high school chemistry, the reaction forumula would be:

2AgOH –> Ag2O + H2O

Silver Oxide is slightly soluble in water, and after electrolyzing for a while you have an ionic silver solution, not colloidal silver. You can prove that silver ions exist at this point by adding a small amount of table salt as a test. The salt will form silver chloride which will precipitate out to form a cloudy liquid because the solubility of silver chloride is 5 times less than silver oxide.1

If the electrolysis is continued, the silver oxide will reach saturation, and then will start to precipitate as colloidal silver oxide. At this point, the solution will start to show the Tyndall effect. This is not strictly colloidal silver, although it does have anti-microbial properties according to the EPA2 Silver oxide is what gives CS its metallic taste which is another indication you have made silver oxide instead of colloidal silver.

This is what most people make and call colloidal silver.

II) High Temperature Colloidal Silver method

If the same method as above is performed while the water is close to boiling temperature, an additional reaction happens. Silver Oxide reduces to metallic silver when close to boiling in the absence of free oxygen3. This makes a straw colored colloidal silver product. The yellow color is caused by the plasmon effect of the extremely small silver particles.

The spontaneous reaction that reduces the silver oxide to silver is:
2Ag2O –> 4Ag + O2

The result is then a solution containing very little silver oxide (ionic silver) and a majority of metallic silver particles. This can also be tested by the addition of some salt. Unlike the CS made at room temperature, this CS does not turn cloudy with the addition of chloride ions showing that it contains few silver ions. This is true colloidal silver.

III) Distilled water + salt + silver anode.

Some people add a little table salt to jump start the electrolysis process. This method produces silver chloride, which has very low solubility and thus produces a cloudy solution. Silver chloride is very photosensitive, and is used in the production of photographic paper. When ingested, silver chloride ions travel into the skin, and are photo reduced by sunlight to metallic silver which then becomes trapped in the skin and cannot be removed. This causes the skin discoloration called Argyria as the amount of silver trapped in the skin increases over time. Ingesting silver chloride is definitely not a good idea.

IV) Distilled water + sodium hydroxide + silver anode + corn syrup

This is just one of the chemistries that makes superior metallic colloidal silver. The sodium hydroxide and corn syrup work together as a reducing agent to transform the silver ions to silver metal. What is left behind is a miniscule amount of sodium and sugar plus the colloidal silver itself. Sodium hydroxide is a widely used food additive (Its what makes the skin on pretzels).

Which method is better?

Definitely not method III, with salt. Ingesting silver chloride is simply asking for trouble in my opinion.

Method I, the most common way of making CS would seem to be safe however it probably does not remain silver oxide when ingested. The stomach is a chloride rich environment which will convert silver oxide to silver chloride as soon as it is swallowed. Do people take enough silver oxide to be a problem? I don’t know. Perhaps silver chloride is not readily absorbed by the body, but then why is that the people who developed argyria use salt to make their CS? Maybe its simply the dosage.

Method II gets rid of a lot of the ionic silver content, but there will be some residual ionic silver remaining. This is definitely better than method I though.

Method IV is my personal preference, as I know the true metallic CS will not react with stomach acid to make silver chloride, and it has an excellent shelf life, even when exposed to light. I have a sample over 2 years old in a clear glass bottle exposed to light every day, and it has not yet degraded. Using a food based reducing agent insures that all ionic content is removed, and the small amount of sodium involved is less than found in 3 or 4 french fries.

There is some controversy over which kind of colloidal silver is the better antibacterial agent. Some research papers show that ionic silver is 4 times better at killing bacteria but 25 times more toxic to human fibroblast cells. It is pretty clear though that ionic silver poses the greatest risk of turning the skin blue (argyria).

For a detailed look at how to make Colloidal Silver, see my Colloidal Silver page.


1) Solubility of silver species
Silver Oxide 0.00250 g/100 ml (20C)
Silver Chloride 0.00052 g/100 ml (20C)

2) US EPA Registration Review Schedule: Antimicrobial Pesticides of October, 4, 2006

3) I first discovered this when attempting to make CS using one submerged silver electrode, and one silver electrode suspended 1/8th inch above the water. I then applied 4000 volts from a transformer to create a plasma arc from the suspended electrode to the water surface. This created a clear CS (as tested by the salt method). I noticed that after a time, a yellow to brown layer would form at the top of the solution as it heated up from the plasma arc. As the arc continued to heat the solution, the brown layer would grow further down from the top. I did not know why until recently when I found reference to the decomposition of silver oxide to pure silver at boiling temperature in the absence of oxygen.

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