Saponification of stearic acid

[Elkins45]

I have a jar of stearic acid that I bought from a candle shop. I've been reading about the stuff and how what I really need is sodium stearate because the Na+ end helps "build a bridge" between polar and non polar. THe sodium stearate has a hydrophilic end and hydrophobic end.

So f I want to make my stearic acid into something really useful to bind my lube together, it would seem that all I need to do is saponify it in a 1:1 molar ratio with good ol' sodium hydroxide (lye). I guess I'm off to the old hardware store or small town grocery to see if anybody still sells lye for drain cleaning or soap making. Wally world doesn't carry it anymore, at least not around here.

Has anybody here done this before. I assume the process is similar (including similar hazards) to homemade soap making?

[btroj]

Same as making soap.

Far easier to just go buy a few bars of Ivory soap.

[1874Sharps]

I have done it in the laboratory when I used to work as a chemist, but the chemicals were supplied so I never had to procure them. I imagine NaOH is not readily available, but still can be found. Just be very careful to wear proper eye protection if you wind up using it, as hydroxide in the eye is very bad. Hydroxide can cause serious chemical burns on the skin as well.

[geargnasher]

Same as making soap.

Far easier to just go buy a few bars of Ivory soap.

BINGO! Plus no residuals and not as much glycerin content as you will have from the saponification reaction.

Gear

[btroj]

Ummmm, glycerin?

Why would there be glycerin from saponification of stearate acid?

From a fat, yea. Those are triglycerides, this is a single fatty acid.

Sorry Gear, had to call you out.

[Elkins45]

Well, I already have the steric acid so I might as well turn it into something useful.

[bruce381]

a basic acid like stearic will react very fast with a cautic melt the acid if you can then with eye protection and all the saftey things, gloves,face mask,ai re breather,haz mat suit etc. add in a diluted KOH or NAOH solution maybe a 10%.

[geargnasher]

Ummmm, glycerin?

Why would there be glycerin from saponification of stearate acid?

From a fat, yea. Those are triglycerides, this is a single fatty acid.

Sorry Gear, had to call you out.

Ahhh! Yer right about that, I was thinking using the fats where you have all the other by-products to deal with.

Gear

[nanuk]

Hey, is there a thread discussing the benefits of Stearic Acid VS Sodium Stearate?


I remember some time back that the S.Acid worked fine, but then read a blurb about rusting... but can't find the refering threads...

TIA

[Elkins45]

My understanding is that sodium stearate is what lubes need because of the sodium end of the molecule, which allows it to have one end be hydrophilic and the other be oleophilic. That is how it binds the different components together. Stearic acid is essentially 1/3 of a triglyceride without the glycerin.

There's a pretty good explanation here: http://en.m.wikipedia.org/wiki/Sodium_stearate

[geargnasher]

Felix lube made with stearic acid per the Wiljen recipe rusted two of my rifles and corroded gas checks and brass, and reacted with the iron in my sizer enough to turn the lube almost black. I don't clean my gun bores normally, and was confident in my regimen with 'normal' Felix lube, but when I made a new batch with stearic acid it caught me off guard, hence the rusting.

Gear

[nanuk]

Gear, that is the confirmation I needed

thanks

'nuk

[crabo]

I have a jar of stearic acid that I bought from a candle shop. I've been reading about the stuff and how what I really need is sodium stearate because the Na+ end helps "build a bridge" between polar and non polar. THe sodium stearate has a hydrophilic end and hydrophobic end.

So f I want to make my stearic acid into something really useful to bind my lube together, it would seem that all I need to do is saponify it in a 1:1 molar ratio with good ol' sodium hydroxide (lye). I guess I'm off to the old hardware store or small town grocery to see if anybody still sells lye for drain cleaning or soap making. Wally world doesn't carry it anymore, at least not around here.



I understand a lot of things, but trying to read and understand all of this makes my head hurt.

[Elkins45]

I understand a lot of things, but trying to read and understand all of this makes my head hurt.

I minored in chemistry, so I occasionally look for places to use the few parts of it I remember :)

[nanuk]

Elkins45
what is the Mole of lye? what is the Mole of Stearic Acid?

better yet, just give me it in grams of each.... and tell me how to mix them

[Elkins45]

According to Google, stearic acid has a molecular weight of 284.5 and lye is very close to 40. If I calculated correctly, a 1:1 molar ratio means you need 7.1 grams of stearic acid for every gram of lye.

Mixing them is something you do VERY CAREFULLY, since acid-base reactions evolve a lot of heat and frequently spatter everywhere when they do it. The chemicals will need to be in solution to react and dissolving lye in water is something that also demands a lot of caution. Wear eye protection, gloves, and do it outside where there's plenty of ventilation.

I picked up some lye today, so I'll run a small scale test tomorrow morning and let you know what happens.

[5Shot]

Felix lube made with stearic acid per the Wiljen recipe rusted two of my rifles and corroded gas checks and brass, and reacted with the iron in my sizer enough to turn the lube almost black. I don't clean my gun bores normally, and was confident in my regimen with 'normal' Felix lube, but when I made a new batch with stearic acid it caught me off guard, hence the rusting.

Gear

This got me worried, as I used stearic acid in my recipe. When I googled Stearic Acid and Rust, it turned up a bunch of links on using Stearic Acid to PREVENT rust on iron.

Do you think something else was at work?

[geargnasher]

It was the only thing different. I just threw a bunch of checked/lubed boolits in the remelt can last night due to corrosion. The lube above the gas check shank was bright blue/green. this never happened with the original recipe. Some loaded ammo has corroded rings inside of the case necks too. Stearic acid instead of sodium stearate is the only thing I changed.

Gear

[5Shot]

Interesting...

[Elkins45]

I decided to pick and can the last of my tomatoes instead of doing amateur home chemistry, so it will be a couple of days before I can report.

[geargnasher]

If you REALLY wanted to make this interesting, you could make your lube all at once (once you got your saponification stochiometry worked out) by adding the soap components to the melted wax/oil. This is how lubricating grease is made, the ingredients are reacted together in the presence of the lube oil and it all gels at a MUCH lower temperature than is required to melt the resulting metal salt later.

Gear

[Pooch]

I use Ivory Soap. It works.

[robroy]

A mole is the measure of how many of a particular particle there are in a sample. Avagadro's number (6.02x10**24) is the number of particles in 1 Mole. So a 1 molar solution of any compound is the molecular weight in grams of the compound disolved in enough water to equal 1 litre of solution. There you go, clear an MUD

[Linstrum]

Glycerin is hydrophylic (likes water) and it absorbs it out of the air. Back when glycerine bottles had iron lids the lids always rotted out very quickly, and I suspect there is more to the rusting reaction when glycerine is present than meets the eye, it could be that the iron catalyzes hydrolysis of the glycerine and releases an odorless dicarboxylic acid, hence the all-out-of-proportion rusting of iron lids on glycerine bottles. Iron doesn't rust very fast in an alkaline environment, that is why iron rebar in concrete lasts so long, except around salt water because the salt acts as an electrolyte. Anyway, lubes other than hydrocarbons need to be alkaline to preserve a firearm. if there is glycerine in any lube that comes in contact with guns, it is BAD NEWS! So's salt, hence don't use corrosive primed ammo without washing the heck out of the barrel IMMEDIATELY afterwards. I have used Felix's lube without rusting problems, so I suspect that Felix's lube that causes rust is contaminated with some kind of electrolyte like sodium or potassium chloride or an acid. Good old sweat from your fingers, especially if you drink coffee or soft drinks, can be problematic.

rl 1,140

[geargnasher]

Good info, Linstrum, thanks!

Gear

[btroj]

But there is no glycerine present in stearic acid. It is a fatty acid, not a triglyceride.

My supposition is that stearic acid makes the lube have a mildly acidic pH which cause the rust.

In the end, does it matter why? It happens, Ivory soap is cheap and available, so why mess wi it?

[Linstrum]

Hi, btroj, yep, thanks for re-pointing out your concern, I pretty much ran right over the top of it. Sorry. You are absolutely correct about no glycerine or glyceryl being present in stearic acid. Or at least there shouldn't be in pure stearic acid. "Triglycerides" is one of the several correct names for many of the class of plant and animal fatty compounds that include glyceryl stearate, which is an "ester" in chemical terms besides also being 1/3 of a triglyceride. Stearic acid does not dissociate into H-plus and stearate-minus like most of the water soluble acids do, so it does not have any acidic or electrolytic reactions to rust iron like the strong mineral acids such as sulfuric, hydrochloric, nitric, etc., and all common water soluble salts of stearic acid are highly alkaline through hydrolysis, which is why Ivory Soap burns the heck out of your eyes.

Iron will not appreciably rust in an alkaline environment, which is why steel rebar in concrete doesn't rust except when in contact with strong salt water from road salt and sea water.

The reaction between water and sodium stearate that produces an alkaline solution has two main parts (for simplicity's sake it has two parts, actually all the steps are not all that well understood at the atomic level), where the sodium stearate dissociates into two particles in water solution, which are a positive sodium ion and a negative stearate particle that immediately satiates itself by grabbing off the first hydrogen ion it gets close to from any nearby water molecule. Grabbing off a hydrogen ion from a water molecule is called "hydrolysis", and from the H2O water molecule (H2O can also be written as H-O-H to help visualize what happens) it leaves behind an OH-minus hydroxide ion, which is perfectly alkaline. The end results are the same as having a mild lye (sodium hydroxide) water solution. The story isn't over yet, the hydrolysis reaction between water and sodium stearate is fully reversible, and because of that, there never gets to be any insoluble stearic acid floating around on the water because an equilibrium point is reached in the hydrolysis reaction. To get stearic acid itself back again, just add some strong highly dissociated water-soluble acid like hydrochloric acid to the solution and it neutralizes all the hydroxide ions swimming around to make water again plus it donates hydrogen ions to all the stearate ions that turns them back into insoluble stearic acid that floats to the top. The other part that is ultimately left is sodium chloride, also known as table salt.

If you use sodium stearate to take a bath and don't live in the Rocky Mountains or Minnesota, all hell breaks loose because there is "hardness" in your water that leaves a dirty ring around the bathtub and gunks up your hair with insoluble calcium and magnesium stearate. That is why detergents were invented for the folks who don't live in Colorado or The Land Of 10,000 Lakes/Sky-Blue Waters.

Sorry about all the details. I never thought I'd regurgitate one day at a time all the chemistry class lectures I had plus re-write my chemistry books one page at a time almost half a century later. But being a chemist all these years has been fun, especially here!

From The Land Of Two Lakes/Mud-Brown Waters, also know as New Mexico, where all that mud-brown stuff floats around in the air that we tell out-of-state folks is the "Enchantment" part in our state motto "The Land Of Enchantment". By the way, one lake is Elephant Butte Lake over on the Rio Grande River, but I don't where the other lake is, I think it wandered off looking for some fish and got lost in the last big rain we had awhile back that also introduced the concept of "getting wet" to the inhabitants of Taos. If you visit here, bring some White Rain shampoo with you. If you don't, you'll regret it.

rl 1,141

[btroj]

I am very well aware of the behavior of weak acids and bases. A BS in Chemistry taught me that.

What I am thinking about is a galvanic reaction facilitated by the stearic acid. The brass case and the bullet have different compositions and different galvanic potentials which would allow a reaction. The stearic acid could well be a viable "electrolyte" allowing the electrons to flow.

I have never made Felix lube with stearic acid. I have not personally had corrosion of brass due to any lubes. What I do know is that Gear made a batch of Felix lube with stearic acid instead of stearate and he had corrosion occur. Tells me that the stearic acid had effects on the brass that I am not interested in.

I have a jug of lab grade sodium stearate I use for my lube making so it is of no concern to me.

Moral of the story's that a similar sounding chemical may not give similar results. Be certain of what you are using.

[Linstrum]

Hi, btroj! I hear what you are saying about the stearic acid taking part in the corrosion, and my guess is that the catalytic properties of iron, iron oxides, copper, or copper II oxide might be involved in the stearic acid being oxidized in contact with them to make a water soluble electrolyte that may be an organic acid. Carboxylic acids like formic acid will corrode the heck out of brass and iron, especially when there is a source of electric current present. As you know, lead is pretty inert compared to copper, iron, and zinc; hence they will corrode in a galvanic reaction with lead as one pole. But to complicate that, boolit metal contains other stuff besides lead, and a few of the alloying constituents are highly reactive compared to the lead (tin is not). It is a real can of worms, for sure.

If you are getting into corrosion of cartridge brass, you are opening a whole can of worms because the zinc is amphoteric while the copper is not, but both form Werner coordination complex ions, and both properties can complicate the heck out of everything. Over-all they pretty much follow the basic rules of the Electromotive Series of the Elements, but all sorts of other side reactions also take place that are not directly governed by the voltage potentials of copper and zinc according to the standard Electromotive Series potentials.

70% Cu-30% Zn cartridge brass has some pretty interesting corrosion problems generated by its two metals in intimate contact with each other. The most common thing with it is what is called "plug de-zincification" where the brass is in contact with iron. Plug dezincification is most commonly seen in .30-06 cartridges stored for a long time in Garand en-bloc clips. It is not a simple galvanic reactions, zinc being amphoteric while copper is not, along with both forming Werner Coordination Complex ions are involved. But the end result is that both the zinc and copper get dissolved into solution by galvanic action but the copper immediately gets electroplated right back onto the surface of the brass, leaving a very bright shiny copper-plated spot around a deep pit or hole through the cartridge. Around the tell-tale shiny copper spots are deposits of white zinc hydroxide and carbonate, as well as apple green deposits of copper carbonate and copper hydroxide.

rl 1,142

[geargnasher]

I know that copper carbonate is "verdigris", but what about copper hydroxide? I'm trying to explain the green fuzz in my case necks, blue-green lube next to gas checks, and the bright orange, fine rust that formed in my gunbarrels with the stearic acid lube. We must also consider that the lube was exposed to the reaction of burning smokeless powder and the residue left exposed to air for weeks.

Gear

[Linstrum]

Verdigris is more than one compound, usually a mixture of copper carbonate and copper hydroxide that form from contact with air and rain water. Copper acetate is also called verdigris, but is traditionally made with acetic acid (vinegar). The green stuff on your cartridge necks is very likely a whole duxe mixture because of the great number of products it was exposed to from combustion of smokeless powder.

Orange powder is usually red lead oxide. Back when gasoline had tetraethyl lead in it, the red-orange deposits on the stem side of exhaust valves in engines was red lead oxide formed at high temperature. Welding steel that has lead solder on it gets orange from the lead oxide, back when I did wreck repair on cars I got into lead used to smooth sheet metal joints on car bodies when I gas welded new panels in. That was nothing but trouble because lead and iron make an alloy that is as strong as a potato chip. In gun barrels the orange powder red lead is from blow-by gas cutting the boolits using a very hot powder like Bullseye or the old WW1-WW2 Cordite the Brits used in the .303. That long ago outlawed enameled cast iron cookware from Italy, Spain, and Mexico with bright red-orange exteriors and gray interiors was colored with red lead oxide and killed countless people because tomatoes were cooked in it and the citric acid dissolved out the lead. Glad they quit making it.

rl 1,143