snaxforgandhi
On a mission...apparently
- Joined
- Jul 24, 2009
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THIS IS MEANT AS A COMPANION POST TO TATER'S EXCELLENT "Make Your Own pH Down For Pennies!"* POST. IT INVOLVES PROCURING SULFURIC ACID FROM AUTO PARTS STORES AND IS A POSSIBLE SAFETY ISSUE. *URL="http://www.marijuanapassion.com/forum/showthread.php?t=37804
{{{READ THIS FIRST!!! Added 10/18/2009 @ 01:59: Hey, something wasn't sitting right with me after I wrote this post, kept nagging at me. I took a closer look at Tater's formula - and I'm really sorry Tater, not trying to be a jerk - but it's wrong*. I'm assuming that he got his figures from a well known recipe because his numbers were exactly the same; 50ml of sulfuric solution to 950ml of distilled water = a ratio of 1:19 H2SO4 solution to H2O and has been the standard formula for a common sulfuric acid based homemade hydroponics pH down for ever. He was right on the money there. Where he went sideways was his assumption that the concentration of the sulfuric acid solution to be mixed was what he called "pure" H2SO4, which would actually be "concentrated" as I have already layed out in the following post. However, this formula actually assumes that you're starting with 33% solution. If you mix this formula using concentrated 97% H2SO4 you will end up with a nearly 5% solution. This is more than twice the intended concentration for this formula, which will result in a 1.65% solution if 33% H2SO4 is used. This may seem like a small difference, but due to the exponential nature of ionic dispersion (H+) in a non-buffered solution it'll pack a wayyyy bigger punch! It'll work but it's much more touchy and at 5% it's also much more hazardous to handle. Think of it like this: The area of a 9 inch circle is more than twice the area of a 6 inch circle, even though it's only 1/3 larger in diameter. There's nowhere near enuf room to explain all this, just trust me. Sulfuric is what is known as a strong acid, meaning dispersion of hydrogen ions (H+) in solution is 100%, and as H2SO4 gives up 2 protons to HCI's 1, it has twice the molarity per given mass, and makes for a touchier solution that's more sensitive to little changes than most commercial solutions.
Here's the simple version:
Mix 50ml of 33% sulfuric solution (read this post to learn how to determine what you bought) to 950ml of distilled water for 1 liter of a 1.65% pH down solution (50x0.33=16.5=10^3x0.0165=1.65%)
or,
Mix 70ml of 33% solution to 890ml of distilled water for 1 U.S. quart of 2.4% solution (70x0.33=23.1=960x0.024=2.4%).
To use the 1.65% solution mix approx. 5ml(1tsp)/liter for a drop of 1 pH point, and to use the 2.4% mix approx. 15ml(1Tbs)/gal. for a drop of 1 pH point. THIS IS APPROXIMATE and to a greater extent than commercial pH down will depend on the TDS/EC and degree to which your water source/nutrient solution is naturally buffered (remember, everything is a bit touchier with a sufuric pH down) You'll have to experiment to find the perfect ratio for you, and though sufuric acid solutions are a little more sensitive, it's totally worth it for how much $$$ you can save. Tater was right on the money there!
All I have corrected is Tater's numbers in relation to the molarity of the sulfuric acid source. Please follow everything else he says in terms of mix order, caution, etc.. Read on to learn how to know what you're buying so you can start with the right stuff. Love peeps! }}}
Greeting Earthlings!
Fairly new to the forum, but I've been producing pH up/down for years (among other interesting forays into organic chemistry). First: I got nothin' but love for Tater!! I'm totally, unequivocally and thoroughly onboard with your independent initiative Tater. Believe that. Also, I have zero use for the "You'll put your eye out!" crowd myself. (I'm a big boy and they even let me use the grown-up knives at dinner!)
I offer the following humbly and purely in the spirit and belief that knowledge is the greatest tool and most powerful weapon in the world. We are all capable of many things (including handling strong acids and bases) but we need solid instruction.
All I want to do is clear up a couple things.
1. YES!! Sulfuric acid makes a dynamite down agent and you can totally make your own at home! BUT, your statement that sulfuric acid is commonly known as "battery acid" isn't quite accurate - at least as far as auto parts stores go - and could be, at the least, a practical problem and, at worst, a safety issue. The culprit here is confusion and I want to avoid it is all.
So...
Not So Important...
Some automotive and motorcycle parts stores do indeed sell concentrated sulphuric acid (calling it "battery" acid 'cuz that what it's used for in this industry), which is generally 97% or 98% pure. However, 100% "pure" H2SO4 is not sold because sulfuric acid loses sulfur trioxide (SO3) at boiling point, reducing concentration to a little better than 98%. So, the words pure and concentrated mean specific things in chemistry, and it can REALLY matter sometimes.
Much More Important...
Automotive and motorcycle parts houses also carry a product called "battery acid," or "battery fluid," which is a premixed - and sometimes buffered - solution of 33% (4.2 molar) sulpfuric acid in solution with distilled water. Also, it has been my experience that a parts store will carry either one (97%) or the other (33%), but not both. NOTE: 99% OF THE PEOPLE WHO WORK AT THESE STORES DON'T KNOW THE DIFFERENCE AND IT ISN'T USUALLY REFERENCED ON THE PACKAGING!!!
Both the concentrated and premixed come in boxes with the big scary NFA panel and huge warnings with pictograms showing acid burns to human flesh and reactive metals. Neither typically indicate the concentration anywhere on the packaging. Figures 1-5 are examples of both concentrated 97% sulfuric and premixed 33% solution. Can you tell the difference?
The reason this is important is because the 1st post in this thread is calling out specific ratios (50ml H2SO4/950ml distilled water) that assume a concentrated sulfuric acid component of 97% purity. *((THESE NUMBERS ARE WRONG! READ ADDENDUM ABOVE!!)) Obviously it will not produce the same final product if what you're calling concentrated acid is, in fact, only 33% pure. Conversely, if you bought 33% solution one time, mixed it until it worked, then got some "battery" acid at another store and it turned out to be 97% and you mix it to the same ratios you're gonna totally zap your 'nutes and/or roots, and just might fry your hands in the process.
HOW TO TELL THE DIFFERENCE SINCE RETAIL CONTAINERS RARELY SPECIFY CONCENTRATION: First, don't ask the counter help; often people will answer questions that they are not qualified to answer in an effort to be helpful. This is especially true of retail clerks whose job it is to "help" the customer. It's well-meant but not very reliable.
So here's the deal: Concentrated sulfuric will have instructions in the box on how to create a solution by mixing with distilled water. Premixed "battery acid/fluid" will instruct the customer to add it as-is to the battery cells.
So...
One is "battery" acid, meaning: "Acid that is to be mixed with water and then added to a lead/acid battery,"
The other is "battery acid/fluid," meaning: "The already mixed stuff that is ready to go into your battery right out of the bottle/pouch/bag."
Again, I only mention any of this 'cuz I want everyone to have success and safety in all their growing endeavors, and that's what MP is all about, right? Love peeps!
~Snax (He Who Lurks)
{{{READ THIS FIRST!!! Added 10/18/2009 @ 01:59: Hey, something wasn't sitting right with me after I wrote this post, kept nagging at me. I took a closer look at Tater's formula - and I'm really sorry Tater, not trying to be a jerk - but it's wrong*. I'm assuming that he got his figures from a well known recipe because his numbers were exactly the same; 50ml of sulfuric solution to 950ml of distilled water = a ratio of 1:19 H2SO4 solution to H2O and has been the standard formula for a common sulfuric acid based homemade hydroponics pH down for ever. He was right on the money there. Where he went sideways was his assumption that the concentration of the sulfuric acid solution to be mixed was what he called "pure" H2SO4, which would actually be "concentrated" as I have already layed out in the following post. However, this formula actually assumes that you're starting with 33% solution. If you mix this formula using concentrated 97% H2SO4 you will end up with a nearly 5% solution. This is more than twice the intended concentration for this formula, which will result in a 1.65% solution if 33% H2SO4 is used. This may seem like a small difference, but due to the exponential nature of ionic dispersion (H+) in a non-buffered solution it'll pack a wayyyy bigger punch! It'll work but it's much more touchy and at 5% it's also much more hazardous to handle. Think of it like this: The area of a 9 inch circle is more than twice the area of a 6 inch circle, even though it's only 1/3 larger in diameter. There's nowhere near enuf room to explain all this, just trust me. Sulfuric is what is known as a strong acid, meaning dispersion of hydrogen ions (H+) in solution is 100%, and as H2SO4 gives up 2 protons to HCI's 1, it has twice the molarity per given mass, and makes for a touchier solution that's more sensitive to little changes than most commercial solutions.
Here's the simple version:
Mix 50ml of 33% sulfuric solution (read this post to learn how to determine what you bought) to 950ml of distilled water for 1 liter of a 1.65% pH down solution (50x0.33=16.5=10^3x0.0165=1.65%)
or,
Mix 70ml of 33% solution to 890ml of distilled water for 1 U.S. quart of 2.4% solution (70x0.33=23.1=960x0.024=2.4%).
To use the 1.65% solution mix approx. 5ml(1tsp)/liter for a drop of 1 pH point, and to use the 2.4% mix approx. 15ml(1Tbs)/gal. for a drop of 1 pH point. THIS IS APPROXIMATE and to a greater extent than commercial pH down will depend on the TDS/EC and degree to which your water source/nutrient solution is naturally buffered (remember, everything is a bit touchier with a sufuric pH down) You'll have to experiment to find the perfect ratio for you, and though sufuric acid solutions are a little more sensitive, it's totally worth it for how much $$$ you can save. Tater was right on the money there!
All I have corrected is Tater's numbers in relation to the molarity of the sulfuric acid source. Please follow everything else he says in terms of mix order, caution, etc.. Read on to learn how to know what you're buying so you can start with the right stuff. Love peeps! }}}
Tater said:...A jug of sulfuric acid (also known as battery acid)...
Tater said:.... 5 bucks got me 1.5 liters of pure sulfuric acid....
Greeting Earthlings!
Fairly new to the forum, but I've been producing pH up/down for years (among other interesting forays into organic chemistry). First: I got nothin' but love for Tater!! I'm totally, unequivocally and thoroughly onboard with your independent initiative Tater. Believe that. Also, I have zero use for the "You'll put your eye out!" crowd myself. (I'm a big boy and they even let me use the grown-up knives at dinner!)
I offer the following humbly and purely in the spirit and belief that knowledge is the greatest tool and most powerful weapon in the world. We are all capable of many things (including handling strong acids and bases) but we need solid instruction.
All I want to do is clear up a couple things.
1. YES!! Sulfuric acid makes a dynamite down agent and you can totally make your own at home! BUT, your statement that sulfuric acid is commonly known as "battery acid" isn't quite accurate - at least as far as auto parts stores go - and could be, at the least, a practical problem and, at worst, a safety issue. The culprit here is confusion and I want to avoid it is all.
So...
Not So Important...
Some automotive and motorcycle parts stores do indeed sell concentrated sulphuric acid (calling it "battery" acid 'cuz that what it's used for in this industry), which is generally 97% or 98% pure. However, 100% "pure" H2SO4 is not sold because sulfuric acid loses sulfur trioxide (SO3) at boiling point, reducing concentration to a little better than 98%. So, the words pure and concentrated mean specific things in chemistry, and it can REALLY matter sometimes.
Much More Important...
Automotive and motorcycle parts houses also carry a product called "battery acid," or "battery fluid," which is a premixed - and sometimes buffered - solution of 33% (4.2 molar) sulpfuric acid in solution with distilled water. Also, it has been my experience that a parts store will carry either one (97%) or the other (33%), but not both. NOTE: 99% OF THE PEOPLE WHO WORK AT THESE STORES DON'T KNOW THE DIFFERENCE AND IT ISN'T USUALLY REFERENCED ON THE PACKAGING!!!
Both the concentrated and premixed come in boxes with the big scary NFA panel and huge warnings with pictograms showing acid burns to human flesh and reactive metals. Neither typically indicate the concentration anywhere on the packaging. Figures 1-5 are examples of both concentrated 97% sulfuric and premixed 33% solution. Can you tell the difference?
The reason this is important is because the 1st post in this thread is calling out specific ratios (50ml H2SO4/950ml distilled water) that assume a concentrated sulfuric acid component of 97% purity. *((THESE NUMBERS ARE WRONG! READ ADDENDUM ABOVE!!)) Obviously it will not produce the same final product if what you're calling concentrated acid is, in fact, only 33% pure. Conversely, if you bought 33% solution one time, mixed it until it worked, then got some "battery" acid at another store and it turned out to be 97% and you mix it to the same ratios you're gonna totally zap your 'nutes and/or roots, and just might fry your hands in the process.
HOW TO TELL THE DIFFERENCE SINCE RETAIL CONTAINERS RARELY SPECIFY CONCENTRATION: First, don't ask the counter help; often people will answer questions that they are not qualified to answer in an effort to be helpful. This is especially true of retail clerks whose job it is to "help" the customer. It's well-meant but not very reliable.
So here's the deal: Concentrated sulfuric will have instructions in the box on how to create a solution by mixing with distilled water. Premixed "battery acid/fluid" will instruct the customer to add it as-is to the battery cells.
So...
One is "battery" acid, meaning: "Acid that is to be mixed with water and then added to a lead/acid battery,"
The other is "battery acid/fluid," meaning: "The already mixed stuff that is ready to go into your battery right out of the bottle/pouch/bag."
Again, I only mention any of this 'cuz I want everyone to have success and safety in all their growing endeavors, and that's what MP is all about, right? Love peeps!
~Snax (He Who Lurks)