Hi, I'd like to share an easy way to purify stump remover and fertilizer for nitrate dosing. Granted, one is probably better off just buying food grade KNO3 to begin with ;). I'm not sure if this has been posted before, but here we go.
The process we'll be using is called recrystallization. The solubility of most solids increases with temperature, and in the case of KNO3 it increases by quite a large amount. By saturating the solution at boiling temperatures and then cooling down to just above freezing most of the KNO3 will precipitate out and form crystal structures. Because our starting material is mostly KNO3 and that impurities are of fairly low proportion when we do this the impurities will remain in solution with a small amount of the KNO3.
Materials needed
Stump remover or fertilizer
3qt pot
Fine mesh sieve
Cheese cloth or flour sack towel
Heat proof bowl that will hold 2qt, I suggest pyrex or stainless steel.
Thermometer that reads above 212F
Procedure is as follows.
1. Add about 2lbs of the stump remover or fertilizer to a pot (stainless is best, try not to use bare aluminum) with about 2qts of RODI water. This amount of water is not terribly important as we will boil excess off.
2. Bring this mixture to a boil and stir it until almost all of the solids are dissolved. There will likely be a small amount of insoluble solids or sand and what not.
3. Boil the mixture until it reaches about 230F. You can just bring it to 212F but your will be slightly lower.
4. Pour the hot mixture slowly into through the sieve into the heat proof bowl. Try to leave as much of the solids in the pot. Be very cautious as this mixture is an extreme scalding hazard.
5. Allow mixture to cool to room temperature. KNO3 crystals will begin precipitating almost immediately and continue to grow as the mixture cools. After the mixture is about room temperature cover and place in the refrigerator over night. Also place some RODI water in the refrigerator.
6. Break the crystals off the sides of the bowl. Place the cloth over the sieve and pour the mixture through. Allow this to drain as much as you can. Gather the corners of the cloth and ring the crystals out. Next take the chilled RODI water and using as little as possible wash the crystals. Ring them out again. Repeat once.
7. Allow the crystals to dry. If you wish to dry them in the oven, make sure they are most of the way dried otherwise the solubility will greatly increase and turn them into a sticky mess.
The process we'll be using is called recrystallization. The solubility of most solids increases with temperature, and in the case of KNO3 it increases by quite a large amount. By saturating the solution at boiling temperatures and then cooling down to just above freezing most of the KNO3 will precipitate out and form crystal structures. Because our starting material is mostly KNO3 and that impurities are of fairly low proportion when we do this the impurities will remain in solution with a small amount of the KNO3.
Materials needed
Stump remover or fertilizer
3qt pot
Fine mesh sieve
Cheese cloth or flour sack towel
Heat proof bowl that will hold 2qt, I suggest pyrex or stainless steel.
Thermometer that reads above 212F
Procedure is as follows.
1. Add about 2lbs of the stump remover or fertilizer to a pot (stainless is best, try not to use bare aluminum) with about 2qts of RODI water. This amount of water is not terribly important as we will boil excess off.
2. Bring this mixture to a boil and stir it until almost all of the solids are dissolved. There will likely be a small amount of insoluble solids or sand and what not.
3. Boil the mixture until it reaches about 230F. You can just bring it to 212F but your will be slightly lower.
4. Pour the hot mixture slowly into through the sieve into the heat proof bowl. Try to leave as much of the solids in the pot. Be very cautious as this mixture is an extreme scalding hazard.
5. Allow mixture to cool to room temperature. KNO3 crystals will begin precipitating almost immediately and continue to grow as the mixture cools. After the mixture is about room temperature cover and place in the refrigerator over night. Also place some RODI water in the refrigerator.
6. Break the crystals off the sides of the bowl. Place the cloth over the sieve and pour the mixture through. Allow this to drain as much as you can. Gather the corners of the cloth and ring the crystals out. Next take the chilled RODI water and using as little as possible wash the crystals. Ring them out again. Repeat once.
7. Allow the crystals to dry. If you wish to dry them in the oven, make sure they are most of the way dried otherwise the solubility will greatly increase and turn them into a sticky mess.
