Ionic vs Metallic Silver

Reprinted from Colloidal Silver Forum with permission.

The Controversy:

There is much debate about the superiority of one kind of colloidal silver over the other.  Manufacturers that sell ionic (clear as water) silver say its better than metallic nanoparticles (clear yellow).  Manufacturers of metallic silver similarly claim theirs is the best.  In actuality, ionic is not colloidal silver at all, but a silver compound (usually silver oxide, silver nitrate, silver citrate, etc), but it does kill pathogens.  

Laboratory testing in-vitro (in test tubes or petri dishes) shows that both types kill pathogens, with it requiring about twice as much silver (by ppm) for metallic, but ionic being 25 times more toxic to human fibroblast cells.  However the actual method of action is not fully understood for either type.  Also, in-vitro does not equate to in-vivo (testing with a live subject) testing.  The conditions inside the human body are totally different than in a test tube.  For instance, human cell membranes are negatively charged, and attract the positively charged silver ions, but repel metallic silver particles.  This would waste the ionic silver by binding it to any cell preventing it from attacking pathogens in the blood stream, while metallic silver remains circulating and able to kill pathogens.

Known Risk of Argyria:

One thing is clear though.  Ionic silver is far more likely to cause argyria than the metallic.  Every scientific study supports this assertion.  The reason this is so is for the very same reason that makers of ionic claim it cannot.

Clear ionic silver is made by running current through silver wires in water.  This can create one and only one thing: silver hydroxide which decomposes into silver oxide.  When consumed, silver oxide further reacts chemically with stomach acid producing silver chloride.  This silver, being ionic is the smallest possible size particle.  It is the size of one single atom of silver, and it is small enough to penetrate human cells.  People who say this is the safest claim that because of its small size, it cannot get stuck in the cells.  However, the error in that argument is that it does not stay ionic.  Once inside the cell, it will react with sulfur or selenium in the cell and produce silver sulfide, or silver selenide.  These compounds are not soluble, and stick to the inside of the cell.  This is well known from biopsies of argyria victims done with a scanning electron microscope which show that the discoloration is precipitated insoluble silver selenide and silver sulfide which is now trapped in the cell.    So the fallacy of the claim is that ions do not remain ions, they precipitate out of the cellular fluid and they tend to grow in size as more silver is absorbed by the cell.

Metallic silver particles, having similar surface charge to normal healthy cells, are not attracted to the the outside of the cell membrane, and are too large to enter cells, being about 45 times larger than a silver ion; so the chances of turning blue from it are much much lower.  Cell membranes are meant to transport needed ions into the cell, and keep large particles out.  The negatively charged outer surface of cell membranes capture ionic silver because of the electrostatic attraction between the positively charged silver ion, and the negatively charged cell membrane.  There is no electrostatic attraction between metallic silver nanoparticles and cell membranes. 

It is well documented in laboratory tests that the size of metal particles is important in their ability to inhibit pathogen cultures.  This relation is due to the number of available particles for a given weight of silver as will be shown later in this article.  Halving the particle size produces 8 times more particles for the same weight of silver.

One thing which should be obvious about the efficacy of silver particles is that they have to have contact with the pathogen to kill it.  A silver particle in one part of the body is not going to have any effect on a pathogen somewhere else.  The actions an atom of anything can do is limited, and assuming no nuclear reactions:

A) It cannot summon a pathogen, or in any way attract it to itself except at atomic distances, or be attracted to a pathogen from a greater distance.  It must be close enough to exchange electrons.  This implies random encounters, so more particles gives a higher chance of a pathogen and a silver particle encountering each other.

B) It can donate an electron to something else if its a neutral atom which would convert the metal atom to an ion.

C) It can take an electron from something else if its an ion which would convert the ion to an atom.

D) It can stick to something else by adsorption.

E) It can bang into something imparting force and momentum.  This is an unlikely method of action.

That being the case, then one would expect ionic silver to win hands down over metallic since the same weight of ionic silver contains many more individual particles than silver nanoparticles do.  However, this is not the case.

Physical Differences:

One huge difference between a silver nanoparticle and a silver ion is its effective charge (Zeta potential).  A silver ion carries a positive charge because it is missing an electron. A silver metal nanoparticle appears negatively charged because of the outer surface electrons.  This makes silver metal nanoparticles strongly attract to relatively positive charged pathogens, while silver ions attract to negative charged healthy human cells.

A silver ion is one single atom, whereas a metal nanoparticle contains many atoms. The number of atoms in a nanoparticle can be estimated based on the packing ratio of spheres and the diameter of the particle.  Think of filling a bucket with golf balls.  Even though the bucket is full of golf balls, you can still pour an appreciable amount of water into the bucket.  The volume of the golf balls related to the volume of the bucket is the packing ratio.

The diameter of a single silver ion is 0.33 nm (nanometers, or billionths of a meter) compared to a metal particle of 15 nm.  The particle is about 45 times larger in diameter than the ion.  The best possible packing ratio for small spheres packed into a larger volume is about 74%.

Therefor we can calculate the number of atoms in a 15nm diameter nanoparticle would then be (15 nm / .310 nm)^3 X .74 = 83,800 (approximate) and for a 14nm particle the number of atoms would be 68,160 approximately

So, a 20ppm ionic silver solution should contain 68,000 times more individual particles then yellow metallic colloidal silver for the same amount of silver by weight. (same ppm)

Since there are so many more ionic particles, one would expect the efficacy of ionic silver to be 68,000 times better.  But its not!  According to lab testing, ionic is only slightly better, and then only in certain circumstances.  It in fact takes 68000 ionic particles to match the efficacy of a mere 29 15nm diameter particles.

So what could be possible explanations for this discrepancy?

Possible Causes for Metallic Silver to Outperform Ionic In Vivo:

A)  Ionic silver has no effect at all on pathogens, and the effect that is seen is due to some amount of metallic nanoparticles present.  There are plenty of agents in the human blood stream which can reduce silver ions to metal nanoparticles.  Glucose for instance is very good for that purpose, and is found in the blood.  The normal amount of glucose in the blood of a human is about 1 gram per liter.  This is far more than enough to reduce all the ionic silver to metallic nanoparticles, although the reaction will be slow at body temperature and a large part of the silver ions may already be sequestered inside normal cells (cause of argyria).  This does not contradict laboratory testing of ionic silver on bacteria as lab testing shows that the exudate from bacteria is also a reducing agent again pointing to silver particles as the active agent.

B)  Ionic silver is only slightly effective, but the sheer number of particles makes up for it.  (But why?, either it can kill a pathogen or it can’t)

C)  Metallic silver particles while less in numbers can kill multiple pathogens before being used up.  This seems likely as there are many silver atoms on the surface of the particle available to interact with a pathogen.  Removing one or deactivating one leaves many more.

D)  Ionic silver is deactivated  by reacting with selenium and sulfur compounds in the blood.  This is known and is simple chemistry.

E)  Chemically reducing something on or in a pathogen (Silver metal atom gives an electron) is more effective at killing it than oxidizing something (Silver ion taking an electron).  It may also be that the sheer size of a metal silver particle is able to block a respiratory pathway of the pathogen, or may block a surface receptor site.  It has been shown that metallic silver will bind to the receptor sites of the HIV virus blocking its ability to infect other cells.

F)  Most of the silver ions are sequestered by being ingested by healthy cells and do not have the opportunity to kill any pathogens.  Cell membranes attract and ingest metal ions needed to survive (sodium and potassium mostly), the majority of the silver ions will be captured by normal healthy cells and rendered useless in fighting pathogens traveling in the blood and lymph systems.  This is very likely. Also, the chemistry of blood is a reducing agent for silver (high level of blood glucose), so ionic silver cannot long exist in a blood environment.

Particle Size Considerations:

Doubling the particle size decreases the particle count for the same weight of silver by a factor of 8, but increases the surface area of the individual particles by only a factor of four.  So a doubling of particle size halves the effective surface area.  Conversely, halving the particle size then doubles the total surface area.  But the number of particles is also important, so thinking purely in terms of the surface area of an individual particle is not the best way to analyze the problem.  Perhaps we should compare the total amount of exposed neutral atoms for each particle size

We can actually calculate how many atoms are in a particle,  how many atoms would be on the surface, and how many would be available for interaction.

How many particles are there in 1 Liter of 20 ppm silver 14nm in diameter?

1 liter of 20ppm colloidal silver contains 20 mg of pure silver.

20 mg of pure silver is 1.87 X 10-4 moles

1 Mole of any element contains 6 X 1023 atoms

1.87 X 10-4 moles of silver is then 1.12 X 1020 atoms

The number of atoms in a 14nm sphere based on a .31nm radius of the atom, 74% packing ratio is 68,100

From this we can calculate the number of 14nm particles in the Liter as 1.64 X 1015

The numbers are based on an atomic bonding radius of .155 nm for a silver atom.

AgNp means silver nanoparticle.

Particle Size—–

# Atoms——-

% Surface Silver

10 nm AgNp



14 nm AgNp



20 nm AgNp



From the table, it can be seen that increasing particle sizes not only decreases the number of particles for a given amount of silver, but also decreases the number of exposed silver atoms.  For instance just doubling the particle size from 10nm to 20nm decreases the number of particles by a factor of eight.  Is it any wonder that smaller metallic particles work better?  Many sources claim that smaller particles are more effective because they have more surface area.  This is not logical if one particle can kill one pathogen as has been shown with photomicrographs.  This author believes that the real reason is simply that smaller particles means that there are more of them for a given weight (ppm) of silver.  More particles equals a higher chance that a silver particle will encounter a pathogen and kill it.


On a one to one basis of particle counts, metallic silver is far more efficient at killing pathogens than ionic silver with much less risk of causing Argyria.  Also, the particle size of metallic silver is very important in that it determines how many particles are available for killing pathogens.  Based on the findings of scientific research, there is no benefit to consuming ionic silver, and it is actually detrimental as it exhibits significant toxicity to normal cells.  Metallic silver (yellow colloidal silver) is effective against most bacteria and viruses, and doesn’t cause argyria.