# sodium hydroxide vs potassium hydroxide



## Geo (Apr 5, 2012)

i have the opportunity to acquire both in aqueous solution very cheaply. i have a basic understanding of each one alone but im wondering how substituting one for another would work for refining. like as a reducing agent.


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## goldsilverpro (Apr 6, 2012)

Geo said:


> i have the opportunity to acquire both in aqueous solution very cheaply. i have a basic understanding of each one alone but im wondering how substituting one for another would work for refining. like as a reducing agent.



In most cases, they can be used interchangeably. In general, potassium chemicals are more expensive than sodium chemicals. The molecular weight of NaOH is about 40 and that of KOH is 56. Therefore, it would take 56/40 = 1.4 times, or 40% more weight of KOH to do the same job, for example to raise the pH of a solution.

I'm no chemist but I see no way you could use either as a reducing agent.


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## MysticColby (Apr 6, 2012)

How are they supplied? If they are both 1 molar, for example, then it would require the same volume of each to do the same work. GSP is right about the weight difference, but molarity already takes that into account. If it's supplied as 10%, for example, then you'll have to do math conversions to account for molecular weights.

reducing / oxidizing... I am not as fluent in this as I wish I was. Here's a copy/paste that could help work it out:
In an oxidation-reduction or redox reaction, there is an exchange of electrons between two reactants. The species that loses electrons is said to be oxidized. The species that gains electrons is said to be reduced. An example of a redox reaction occurs between hydrochloric acid and zinc metal, where the Zn atoms lose electrons and are oxidized to form Zn2+ ions:
Zn(s) → Zn2+(aq) + 2e-
The H+ ions of the HCl gain electrons and are reduced to H atoms, which combine to form H2 molecules:
2H+(aq) + 2e- → H2(g)
The overall equation for the reaction becomes:
Zn(s) + 2H+(aq) → Zn2+(aq) + H2(g) 

either way, NaOH and KOH should behave identically (for our purposes) in reactions. There is a small difference in their reactivity with some substances, but that shouldn't even be noticed here.


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## Palladium (Apr 6, 2012)

I think he may have meant to say metabisulfite. Only reducing agents i can think of he might have meant to say Potassium metabisulfite or Sodium metabisulfite ?

Potassium metabisulfite has a molar mass of 222.32 g/mole 
Sodium metabisulfite is 190.1 g/mole 

So you'll need to use about 17% more (by weight) of the potassium salt to deliver the same effective SO2 as the sodium salt.


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## goldsilverpro (Apr 6, 2012)

Liquid Caustic

If someone needs a lot of sodium hydroxide, the most convenient form is a 50% commercial solution of caustic soda (a less pure, technical grade sodium hydroxide). It is a fairly thick liquid that contains about 6.38 pounds of NaOH per gallon of solution. A common name for it is "Liquid Caustic." It comes in 55 gal drums, is reasonably priced, and everybody sells it. Here's the MSDS.
http://msds.fmc.com/msds/100000010035-msds_us-e.pdf 

One of the worst jobs in this business is to dissolve solid NaOH in water, especially in large quantities. It's damned dangerous. It generates a lot of heat when it dissolves. If you don't stir it continuously and/or, add too much at one time, it will build up hotspots and throw hot caustic in your face - sort of like adding concentrated sulfuric acid to water. Same result. It dissolves slower than you think. It can easily clump up and harden when it gets wet. Then, it can only dissolve from the outside of the clump.

Liquid Caustic solves much of the safety problem and saves a lot of time, since it's already dissolved. It will generate some heat when diluted and it can spit back if you pour a steady stream into the water without starting the stirring beforehand. Stir at all times - before and during and until it appears totally blended. If not blended, you will see a swirling motion in the solution. When blended, it will look like clear water.

If liquid caustic (or almost any strength of caustic) gets on you, it can burn you as bad as the strongest acid (sulfuric), so treat it with the same respect. Full face shields, gloves, and a lot of pre-thinking before you use it, are mandatory. Liquid caustic is 18.7 Molar. Concentrated sulfuric is 18.4 Molar. NaOH is the strongest common base and H2SO4 is the strongest common acid. 

Liquid caustic is the slickest thing on the planet. If there's some on the floor and you step on it, I guarantee you'll slide and possibly fall in it. Keep messes cleaned up, but it's best to arrange things so you won't get any on the floor to start with. If you even get weak NaOH on your fingers or gloves, it feels slick until it's washed off (same with cyanide), which sometimes takes a long time. When working with caustic, I used to keep a bucket of about 2% HCl, by volume, just to neutralize that awful slickness off my hands (or gloves) that is so hard to rinse off. The HCl will tell you where every little cut on your hand is, but it's easy to rinse off.


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## Geo (Apr 6, 2012)

the caustic soda is 50% and comes in a 1 gallon container for $3.00, and the potassium hydroxide is 10% in a 1 gallon container for $2.00. i have in mind using the sodium hydroxide to convert silver chloride to silver oxide and the potassium hydroxide to remove solder mask. theres at least 100 containers of each available. theres a clearance house here that stocks obscure chemical brands and a quick label check has yielded other chemicals.too many to remember.ill take a notebook and list some of the chems ive seen discussed on the forum and try to determine if its something i can use. they have about ten gallons of sulfamic acid, ive seen it discussed and i need to find out the uses for this stuff because its cheap.


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## Palladium (Apr 6, 2012)

Geo said:


> they have about ten gallons of sulfamic acid, ive seen it discussed and i need to find out the uses for this stuff because its cheap.



http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=12908&p=129091&hilit=sulfamic+acid#p129091


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## goldsilverpro (Apr 6, 2012)

Sounds like a great place, Geo. My kind of place. Who knows how many of those type companies around the US haven't been discovered yet? 

$.47 per pound for dissolved caustic is a great price. And it's already in one gallon containers, so you won't have to (dangerously) pump it out of a drum. If you've got a place to safely store it, I would stock up. Won't the cheaper caustic solution work as well as the KOH for solder masks?

Never, Never, Never get liquid caustic under your fingernails or in your eyes.

How much is the sulfamic and what strength is it?


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## Geo (Apr 6, 2012)

goldsilverpro said:


> How much is the sulfamic and what strength is it?



i didnt get the particulars on the label. the price is $5.00 a gallon. its all grouped together with the floor cleaning products though i assume a lot of it has nothing to do with floors or cleaning. 

the name of the place is "Mike's Merchandise" and its a closeout clearing house. they have a few locations here in the south.my wife likes it because they carry stuff like restaurant supplies (twenty pound single serve butter,sugar,salt,pepper and other commodities for a few dollars)

ill get a list of chemicals names and percentages tomorrow.

they have about 30 or so gallons of the green label muriatic acid for $2.50 a gallon. i really like the full flavor stuff but ill use this till its gone.


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## Geo (Apr 10, 2012)

i went to buy more chemicals at the closeout clearing house and happened to find something i really needed. they were marked $3.95 but i haggled them down to a buck fifty apiece if i bought ten at a time.



im still making list of all the chemicals. theres a gallon of ammonium thiosulfate for $7.00.is this a good buy? there may be more but i would have to dig it out of the pile.


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## Harold_V (Apr 11, 2012)

Geo said:


> i went to buy more chemicals at the closeout clearing house and happened to find something i really needed. they were marked $3.95 but i haggled them down to a buck fifty apiece if i bought ten at a time.


If I was in your shoes, I'd buy all they had. If nothing else, you could resell them to guys on the forum, even asking a modest profit. Everyone would benefit. That's one hell of a good deal. That's the size I used for inquarting and melting of my pure gold. Went through a large number of them over the years. 

Harold


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## Geo (Apr 11, 2012)

thanks Harold, ill return in the morning and see how many they have left. with a place like that you never know what they have tucked away in a corner.i could walk around in there for a whole day and still not see everything.


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