Making KNO3

[taiwanluthiers]

I used the agricultural grade stuff... it is used to add potassium into the plant's nutrient. They are often mixed with some red crap that will need to be dissolved out. Surely they have them...

[Poindexter]

What about recrystalizing KNO3?

 

I started with 553 grams of agricultural grade KNO3 this am, Put it in a clean pan with just enough distilled water to disolve around 165dF, took it on up to 212dF, poured through a coffee filter (got a few pieces of bark retained) and let it cool in room temp air until I had a forest of needle like bright white crystals.

 

I noticed the crystals "started" growing when the water was still pretty hot, bloomed quite generously in a narrow temp range and then stopped growing more crystals at a cooler temp, so I poured of the liquid once the crystals stopped growing.

 

I poured off the remaining liquid, dried my crystals on a cookie sheet on the outdoor grill - and I got 168 grams of product,.

 

The bag says 97%, maybe 99.7% pure KNO3..

 

Where is the rest of my KNO3? (On the tomato plants now I guess, I did pour it out after watching the liquid another hour after the first decant.), and how can I get more of it out of solution next time?

 

I am off to get some more distilled water...

 

Eyeballing it I got maybe 16 grams tops (that's generous) of needle like crystals in the filter paper.

[Seymour]

You can get the water a good deal hotter with all that K+ and NO3- dissolved in there. The boiling point is raised substantially. Look up a KNO3 solubility curve to get the exact data, but I believe the difference in boiling points between plain water and saturated KNO3 solution is in the order of tens of degrees hotter.

 

And saturated at that high temperature will of course contain an appreciable amount more dissolved KNO3 per unit of water.

 

Secondly you can cool it further than room temp, by putting it in the fridge, and so long as your freezer is not too cold there too.

 

Thirdly you could grow crystals from the remaining brine through evaporation and wash them, but I'm in favor of the tomato food use.

 

Do you find the fertilizer stuff you have is much inferior to your recrystallized stuff in practical pyrotechnics?

[Poindexter]

Seymour, I don't know yet. Just home from a grocery run. It occurred to me that "some" KNO3 was still dissolved in the liquid. Also, I had forgotten about colligative properties, but whatever the temp was, i brought my goop to a boil.

 

At this point my first really good bright white batch of needle shaped crystals is in the ball mill with some carbon and some sulfur.

 

I am wondering about ongoing process though. If this batch (I am up to letter O) is particularly good for my purposes than I am going to have to refine the rest of my KNO3 as part of my process.

 

I am working from John Braddock's "Memoirs" (c1829) where he talks about bringing KNO3 to a boil in pure water to leave some impurities behind, and then pouring off the liquid after the KNO3 crystals form, leaving some impurities behind when the boiling liquid is filtered, and others behind in the cool liquid when it is poured off the KNO3 crystals.

 

I was no whiz at chemistry, I did well in High School, got I think a C in general introductory at University and then got a low F in organic.

 

The relevant passage, highly paraphrased, section 20 :

Muriate of Soda is less soluble in boiling water than KNO3 and will therefore be left behind on the filter paper when boiling solution poured through.

 

Each of nitrate of lime' date=' muriates of lime, soda and others are more soluble in cold water than 'nitre' (KNO3) and will be poured off with the cold liquid from the nitre crystals.[/quote']

 

Next i will go with a similar batch size, but put the poured off liquor loaded with "muriates of lime soda and others" back on the stove, add another 168grams of KNO3 to it and see how much I get out the second time around.

 

I caution against the use of an ice bath in this process. I got mostly white crystals, but with some brown gunk in them nearest the edge of the cooling pan.

 

How can I tell I have cycled the liquor enough/ too much and need to start fresh? Just color change in the crystals? Shape? odor?

 

And what the heck, just because I am curious, is a "muriate"?

[schroedinger]

Yeah with a saturated solution of KNO3 you will raise is the boiling point a lot.

And on top it`s quite easy to get an idea of that, it`s called ebulloscopie.

 

To determine this you need to solve this:

For Watter:

 

(100+X)°C = (0,51*(ammount of dissolved ion in mol)+100)°C

 

KNO3 weights 101,11 g/mol

at 100°C 2452g dissolve so we got:

 

2452g/(101.11 g/mol)= 24.25mol

 

KNO3 dissolves into the ion's K+ and NO3-, so every mole of KNO3 generates 2 moles of ion's (by splitting up once).

 

So we got 48.5 mol of ions in our solution.

 

From that follows:

 

(100+X)°C = (0,51*(48,5)+100)°C ---> X°C= 24.735°C or our new boiling point is 124.735°C (without thinking of the KNO3 which can dissolve more after heating over 100°C)

 

Assuming the solubility of KNO3 is raising like before (quite easy, theoretic nearing) we get the solution that 1206.5 g more KNO3 are going to dissolve, which would raise the boiling point again by 11.93 °C, allowing more KNO3 to dissolve until we get a equilibrium. Which should be around 150°C.

 

If you wan`t this to be aqurate you will need to measure the real boiling point and solve this:

 

(((measured temperatur)-100)/0,51)0,5)*101.11g = (Dissolved grams of KNO3 at you actual Temperatur).

 

 

 

@Poindexter:

 

Where is your KNO3, at 20°C still 317 g of KNO3 are dissolved per litre of Watter, so that nearly the ammount your missing now.

 

To get more out, boil you solution, if there is NaCl inside, it will crystallise out before the KNO3 crystallises, but for real if you know your KNO3 is 99%+ why do you wan`t to purify further? There is no reason for that, only thing that would be interesting could be to dissolve everything and filter out non dissolving stuff (if you got any), and then evaporate all Water. Cleaning KNO3 is quite hard by recrystallisation if you allready got low impurities, or you will lose a lot of your KNO3

[Poindexter]

@Poindexter:

 

To get more out, boil you solution, if there is NaCl inside, it will crystallise out before the KNO3 crystallises, but for real if you know your KNO3 is 99%+ why do you wan`t to purify further? There is no reason for that, only thing that would be interesting could be to dissolve everything and filter out non dissolving stuff (if you got any), and then evaporate all Water. Cleaning KNO3 is quite hard by recrystallisation if you allready got low impurities, or you will lose a lot of your KNO3

 

Honestly sir, i am after two things. My wife loves pyrotechnics, but I am an avid shooter. I have switched to BP cartridges for both my sidearm and meat rifle, but matching 1870s velocities over the chronograph with actual bullets has proven to be quite a challenge. Whether it will be harder to find modern smokeless powder for my gee-whiz meat rifle or crack the secrets to matching 1870s BP for my 45-70 remains to be seen.

 

With all 4 kids in college I probably won't need a moose in the freezer every year anymore pretty soon. But a caribou every year and a moose every third year or so is pretty likely. I got brass, lead and primers to last a life time. I need gunpowder type BP sized FF as good as that made in 1866; caribou season opens in 35 days and I can see the bottom of my freezer.

 

For batch N I combined all my -20+30 mesh from batches F-M, tumbled them alone for a bit in the mill and then added 3

grams of graphite to 77grams of BP. My sd (standard deviation) over the chronograph dropped a bunch, almost 75%, but I gave away almost 100fps in muzzle velocity too. I was seeing about 600fps muzzle with 230gr bullets out of 45 Colt where I was averaging about 700fps muzzle unglazed and Hodgdon 777 (also FFg size) was giving me 930fps average with an enviable sd.

 

So I am looking at the whole thing again with Braddock open. By his description my home made birch charcoal is somewhere between good and excellent, flat black to jet black, too soft to scratch polished copper, makes the "tink tink" noise of fine china, golden. And airfloat can't be shipped air, one of our distinguished members already offered, then found out he couldn't legally ship it to me in Alaska.

 

So I am milling batch O now with recrystallized KNO3. I will re-calibrate my pump with a new plunger before I press O. Apparently overpressing even to 1.750 can cost 200 yards of range when firing a 10 inch cannon.

 

If that doesn't work I'll look at separating the 10% clay from my 90% pure S.

 

One way or another I am putting a caribou in the freezer tout suite.

[Poindexter]

Went at it again this evening. I started fresh with about 750ml distilled water and 500 grams agricultural KNO3. First pass I got out out about 150g KNO3 crystals. I recycled the liquid, heated it, added about 200g KNO3 and got out about 200g KNO3 crystals.

 

I recycled the liquid again, add KNO3 to saturation at the boiling point again and stopped. I got back maybe 100g of crystals, but there was an accumulating brown something that I fed to the lawn. The brown stuff passes through a paper coffee filter at the boil, but coalesces and sinks long before the KNO3 crystals appear. It looks very much like the "hot break" proteins those who home brew beer are familiar with, mostly albumin, only definitely brown.

 

On the third pass once I decanted the liquor off my crystals I poured some distilled water into the crystalization basin and was able to rinse the brown crud out from under my KNO3. If I had enough containers I suppose I could have kept going, ie not poured the brown crud into my nearly saturated KNO3 solution, but I was done for today. Or rather, now I am. Good night.

[schroedinger]

Maybe it could help you, if you start of with powder made by the precipation method, and throw this into your mill. If you would do so, you should get a powder with all ball mill properties and propably also better integrated KNO3, as this would be integrated into the charcoal itself.

[WSM]

And what the heck, just because I am curious, is a "muriate"?

 

A muriate is a salt of muriatic acid, also known as hydrochloric acid.

 

A muriate is a chloride.

 

WSM

Edited August 20, 2013 by WSM