pH Down - Acid is
formulated using food grade Phosphoric acid - pure plant nutrient
https://www.reddit.com/r/TheeHive/comments/g2w8fu
H3PO4 + KI -> HI reaction (hydriodic acid)
or Why not try the hypophosphorous (50%) and iodine to make HI......
3. React potassium iodide with ortho-phosphoric acid, recover HI(aq) and HI. The chemistry of phosphorous is complex. Observation indicates that the following are the major reactions:
1) KI + H3PO4(aq) + delta temp--> HI(aq)+ KH2PO4
2) KH2PO4 + KI + delta temp--> HI + K2HPO4
3) additional HI(aq) and HI is obtained throughout the dehydration of potassium phosphate salts and polymerization of same while reacting with potassium iodide at high temperature--400+?C
This method has the advantage of being safe and controllable and uses non watched ingredients. The process is similar to a simple distillation, and requires only the type of glassware normally owned by the clandestine chemist. For 10 liters/day of HI(aq), this method is ideal, requiring only a 22L RB flask and heating mantle. A 12L-10L RB flask /heating mantle will produce 5 liters/day; a 5L RB flask/heating mantle 2.5 liters/day, etc. The heating mantle is a key element in making HI(aq), oil and sand baths will not take the temperature high enough. The tweaker can use a 1L erlenmeyer with single 24/40 neck on a stirrer/hot plate combo and produce 300-400 cc in a couple of hours. (Percent recovery is a function of scale. At larger scales, more HI(aq) will be recovered mol/mol per KI. 92% recovery mol/mol at the 22L scale and larger, contrasted with only 75% at the 1L scale. Why this is true I can only speculate, but it is true nonetheless.)
Now, for the first time on the Hive, this easy method will be explained step-by-step.
GENERAL OVERVIEW:
Disregard everything that has appeared previously on the Hive regarding the reaction of KI and H3PO4. I used TFSE extensively while initially researching this procedure, and without exception, all previous information is unclear, misleading, and, in several cases, made-up bullshit. The HI FAQ on Rhodiumís page, as regards KI and H3PO4, is erroneous. But you can count on my write-up to tell you exactly how to make HI(aq) safely. No bullshit here.
Here is a general overview of the procedure, specifics to follow:
In general terms, you will be mixing KI powder with H3PO4 liquid in a stirred RB flask on a heating mantle rigged for atmospheric distillation. The RB flask will be equipped with an condenser for downward distillation, a receiver to recover HI(aq), and a second receiver/trap filled with dH2O in which to bubble and recover HI.
KI will be converted first into HI(aq), then into HI(aq) and HI as the reaction proceeds. Hydriodic acid will distill at 105 to 127?C. After the initial run of acid is produced and the contents of the reactor cooled, the dilute hydriodic acid will be redistilled to produce HI(aq). The dilute hydriodic acid from the redistillation that comes over at less than 127?C will be reused in subsequent reactions in the HI trap/receiver. No dilute acid should go to waste. Overall efficiency goes way up by recycling the dilute acid into the next batch.
If this procedure sounds complicated, itís not, and your good buddy Argox will shortly give you all the tips, short cuts, and safety considerations that you will need to successfully make HI(aq) the first time.
Making 10L of HI(aq) in a 22L reactor takes one full 24 hour day from start to finish. This includes setting up the glassware and dismantling and cleaning up for the next batch. You need to stay awake during the reaction. The reaction should not be left unattended for more than 10 minutes, the dynamics are continually changing as the reaction proceeds, suck back can be a concern, you need to stay on top of it. It takes the same amount of time in a [deleted], but if you have the resources and knowledge to set up at that scale, youíre a master, not a student, and need no further instruction from me.
The reaction is simple. However, there are two caveats.
Caveat One--there is a white crystalline precipitate left in the bottom of the flask after the reaction is over and everything has cooled--condensed phosphates. This residue is insoluble in hot water and non polar solvents. It must be physically scraped from the flask. (Not a difficult chore with a 1L or 2 L, but with a 3N 22L RB count on breaking at least one neck. On a larger scale the problem can be solved by investing in a [deleted] with a large center flange opening that will allow you to get your arm inside and scrape.
Caveat Two--the majority of HI(aq) is produced at a temperature above the melting point of Teflon. Teflon paddles will melt and make the phosphate residue even more impervious. Teflon stir bars will melt, revealing the magnet. But really, who cares? Donít sweat the Teflon. (After all, once that first hypothetical batch of HI(aq) goes out the hypothetical door, you can afford to buy a $20 sheet of Teflon and cut a dozen new paddles.) Glass-coated metal rods and blades are the answer for the perfectionist in the audience. Just keep in mind that no exposed metal can be anywhere near HI(aq). Drop one little drop on your heating mantle and watch it burn a hole through the aluminum housing on its way to China. COVER your heating mantle with foil--lots of it! Thatís my way of saying that freshly made HI(aq) is very, very corrosive. So donít even think of entering the lab without eye protection, a lab coat, and good rubber gloves. If two drops of HI(aq) can burn a serious indentation into a cast-iron lab stand base, imagine what a splash of acid will do to your skin, or worse, an eye.
Argox
(Hive Bee)
02-22-02 07:10
No 271994
Hydriodic Acid--Step by Step (Part 2)Write-Up
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PART TWO
STEP-BY-STEP INSTRUCTIONS
1. Obtain ingredients.
Ortho-phosphoric acid, (H3PO4) commonly called phosphoric acid, a thick clear syrupy liquid, can be purchased or ordered from the neighborhood hydroponics store. They sell it as ìpH Down.î Conversely you can order it from the chem supply. Donít respond with posts belly aching about how youíre too paranoid or too smart to buy from the chem supply, and need a write-up that is 100% over-the-counter at Wal-Mart. Argox is not the guy to bitch to about chemicals not being available at the corner Circle K. He recently tried to help in that regard and only received grief for his effort. Finding chems is what separates the men from the boys, the serious from the dilettantes. Back to subject. Buy 75% technical grade phosphoric acid--this works best. Phosphoric acid is non watched and OTC. Itís in everything, even Coca-Cola. Next to sulfuric acid, phosphoric is the most common acid on the planet. You can find it on the shelf at the hydroponics store. DO NOT listen to all those posts about how you can get phosphoric acid at Home Depot or the flooring company. That is bullshit. [A personal aside--I think bees should receive a rating, like on e-bay. Except it would be a bullshit rating. The more bullshit you post, the more negative the rating.] The phosphoric acid sold for cleaning tile is only 15-25% acid, the rest is water, surfactants, soap, and stuff that will fuck up the reaction. Make sure you buy 75% technical grade H3PO4. It is strictly OTC, so no bitching. One gallon on the store shelf retails for $us20--be sure and read the label--some ìpH Downî is nitric acid--you want the label to say ìphosphoric acid.î A 5 gallon pail can be ordered from a hydroponics store for $us65.
Potassium iodide, a heavy white crystalline powder, can be bought at the chem supply. It is non watched and non controlled. You can buy it on-line. Technical grade is OK, but most supply houses only stock the USP grade. The higher price for USP grade in the global scheme of things is insignificant, buy whatever is easiest to obtain. USP KI can be purchased for $us36/kg. There is a boom in KI these days, because of the terrorism scare, take advantage of the general panic and buy a lot if it now, you will absolutely go unnoticed. 1.3 kg of KI will yield one liter of HI(aq) at 94% efficiency (very large scale), so order accordingly, before the WOD reads this post and adds KI to the ìList.î
2. Test ingredients.
Determine the concentration of H3PO4 by boiling it. Below is a chart of boiling points for different concentrations of H3PO4. You want yours to boil at 135?. That will indicate 75% acid. If your sample boils at a lesser temperature, donít despair, boil all your acid until it reaches 135? (and then make sure to get 75% next time). You can boil phosphoric acid in an open beaker on the hot plate. The fumes are non-toxic and non-corrosive--they smell like Sprite (because phosphoric acid is used to give soft drinks that citric flavor). H3PO4 is generally unreactive at room temperature--have no fear about mixing room temperature H3PO4 and KI in the RB flask. Nothing will happen. At room temperature, H3PO4 and KI will not react.
H3PO4
Concentration Boiling point
% by weight ?C
0 100
5 100.1
10 100.2
20 100.8
30 101.8
50 108
75 135
85 158
100 261
105 >300
115 >500
3. Mix ingredients
The mol/mol ratio of KI to H3PO4(100% basis) that works best, according to EXPERIENCE, is about 1:1.2. Here is how that is calculated:
1 mole KI = 166 grams
1 mole H3PO4 (100% basis)= 98 grams = 131 grams of 75% H3PO4
1 X 166 = 166
1.2 X 131 = 157
157/166 = 0.946
Therefore, for every ten grams of KI, add 9.5 grams of 75% H3PO4. Nobody will get mad, if you just add equal parts (weight/weight--w/w) KI and H3PO4. Now you understand how I arrived at this simple formula. Although it sounds almost flippant to say add equal parts by weight KI and 75% H3PO4, truth be told this formula was obtained after lots of trial and error. Adding more acid will not increase yield, but you can try it, nothing bad will happen.
As soon as I post this, three or four of the usual suspects will follow up with posts saying that Iím full of shit and that what you really need to do is add water so that all the HI will have enough water to come over at 57%. See, if you figure 1 mole of KI has 137 grams of iodine and with the one proton donated by the phosphoric acid that makes 138 grams of HI, so 138 grams of HI would need 104 grams of water to make 57% HI(aq). Follow me? These arm-chair chemists will then tell you that the equal w/w 75% H3PO4 to KI only adds about 42 grams of water, therefore they will say to add 62 grams of distilled water in addition to the phosphoric acid for every mole of KI. Donít listen to them. Iím heading them off at the pass right now. The reaction just doesnít work that way. (How do I know? I thought of adding more water from the git-go and tried it. Iíve also experimented with every concentration of phosphoric acid from 50% to 105%.) If you add more water, you will only generate a shit load of dilute acid, which must be distilled off before the real acid is made. See, what the arm-chair chemists donít know because they havenít actually done this, is that most of the HI(aq) comes over AFTER all the water from the 75% H3PO4 has distilled off. The bulk of the HI(aq) is formed from the dehydration of 105% H3PO4 at high temperature, a process typical of the complex chemistry of phosphates. The H3PO4 actually polymerizes into long-chain ìcondensedî phosphates and gives off water and donates a proton in the process. This is the water and hydrogen that make most of the HI(aq). And those long-chain polymers are what stick to the bottom of your flask like stink on a pig. And even if Iím somehow wrong on the theory, in practice I am right on target.
Now that you know how much to add, just dump the two ingredients into an appropriately sized flask. Nothing will happen at room temperature. There is no fizzing or effervescence during the entire reaction, so you can fill the flask fairly full. But no more than 60% for a RB, less for an erlenmeyer. But you already know that, right, because you have at least rudimentary lab skills, right? There will be a period of some massive bumping at a larger scale once the water boils off and the polymerization begins, even with agitation, so if you are faint of heart, fill the flask only 30%. At 1L, 3L and 5L bumping is not a problem. The bumping is nerve-wracking at the 22L scale. At [deleted] scale the bumping will make you jump out of your fucking skin. Agitation helps but doesnít eliminate bumping altogether, so if you get scared easy, add less ingredients. Itís really a function of balls versus greed. If you have the pelotas, then load that sucker up, ícause itís a full 24 hours whether you make a little or a lot. If the doors come down, the charges will be the same, as well, so I say go for it.
4. React ingredients
UNDER A FUME HOOD, heat and stir the ingredients--itís that simple. At 65? an obvious reaction will take place. The clear solution will turn dark brown. This is hydriodic acid being formed. Keep the heat on high, donít let off. The solution will begin to boil at 105?C and a small amount of milky white distillate will come over into the receiver.
READ THIS PART--ITíS IMPORTANT. This initial white distillate and the gas bubbles that are generated at this initial stage of the reaction are poisonous. (OK. OK. Hydriodic acid is hardly something you want to drink for breakfast either, but this white distillate is REALLY poisonous, even compared to HI(aq).) You must remove this white milky distillate once the first drops of yellow or brown acid start to come over. So begin the reaction with a small RB flask as a receiver, say 100 to 250 cc. Collect the initial white distillate and stopper it. DO NOT BREATHE this stuff, Iíll explain what it is in a minute. If you do this reaction on a small scale, the white distillate may only be a few drops, get rid of it anyway. On a large scale, it is enough to kill you. You will have a second receiver filled with dH2O to recover HI. However, at the beginning, substitute it for a small flask filled with dilute NaOH solution or the dilute aqua ammonia (ìclear ammoniaî) that you can buy at the grocery store. Why? Because the first distillate and the initial gas contain H2S (the same hydrogen sulfide that I mentioned being deadly poison at the beginning of this long-winded tome). My guess is that since phosphoric acid is often made from the reaction of sulfuric acid on phosphate rock, trace amounts of sulfur remain in the phosphoric acid. HI is a powerful reducing agent (thatís why the ---- guys need it), so there is a redox between HI and any sulfides. (2HI + MeS + delta temp -->H2S + I2 + Me?. And since H2S is less soluble and more volatile than HI, it comes over first.) This is something else the arm-chair chemists wonít warn you against, but count on Argox to keep you safe, if you pay attention. Like I said, the tweaker with the 1L wonít notice anything, but the bee loading up a 22L could end up very sick, if my advice is not followed. Anyway, add any base, preferably NaOH or ammonia to the white distillate under a fume hood before you toss it out and as long as the initial bubbles are taken up in NaOH solution or ammonia solution, and that solution is also poured down the sink, you will never even know that Argox just saved you from a hospital trip or at least from having to suck on your oxygen bottle for an hour or so. (The arm-chair guys will say that HI smells like H2S and that Iím just confusing one with the other--they are wrong--you can get a good nasal dose of HI fumes and apart from the pain, nothing will happen to you. Get a good dose of H2S and you are going to be unconscious in a few minutes. Initially your teeth will tingle, everything will spin, and as you collapse to your knees, you will realize that this is it, you are going to die. If youíre lucky, like me, youíll wake up in the emergency room puking sodium thiosulfate (oh yeah, thatís cyanide poisoning, for which an antidote exists--if you breath H2S, youíre shit outta luck--thereís no antidote). Anyway I digress: HI smells rotten, but pales in comparison to the deadly stench of H2S.
After getting rid of the initial milky white distillate and taking up the initial bubbles in a dilute base and throwing both away, connect your two regular receivers. This is an atmospheric distillation, so relax. Just keep the heat on high and the overhead or magnetic stirring going. On a smaller scale, stirring is not necessary. For bees with big equipment who lust after the perfect yield, stir.
The reaction is not over when all the brown acid has boiled out of the reactor, it has just begun. Keep the heat on high and watch in amazement as more and more and more acid keeps forming in the condenser. Donít worry about the thermometer at the still head going above 127?C, it is still HI(aq) coming over, just the temp inside the reactor is getting HOT. At 400?C both HI(aq) and HI will come over. Lots of HI at a larger scale, so be prepared for it. About 10% of the total acid production will be in the form of HI that must be collected in the water trap/receiver. HI is exceedingly soluble in water and the dissolution is exothermic, so stirring is not absolutely necessary, but cooling is. More than 10% of the total acid comes over as HI, but most of it is being absorbed by the liquid in the receiver catching the distillate. That is why you keep the dilute acid in the receiver even after the 57% acid comes over. If you remove the initial dilute acid and then collect the 127?C boiling fraction (HI(aq)) as a separate fraction, then to your dismay, you will have loads of HI coming over that must be caught in water. And then you will find that the hydriodic acid in the receiver is incredibly concentrated-- 70% not 57%. The 70% acid gives off so much fumes that handling it is a challenge. So just let ALL the acid collect in the same receiver flask, make sure your receiver is big enough, and you wonít have to deal with much actual HI gas.
{If you donít have a clue about how to set up a for atmospheric distillation with a still head and condenser and water traps and such, and donít know about RBs and heating mantles, and how to control suck-back, and if none of what you are reading makes much sense, and especially if you donít have a good fume cabinet--PLEASE donít try this. There are less dramatic ways to kill yourself than producing a shitload of HI(aq) and spilling it.}
The reaction is over when no more HI(aq) or HI is produced. The reaction is over when no more acid drips into the receiver and/or suck-back begins to be a real problem in the water trap (suck-back with HI is violent--the most violent of any gas Argox has ever worked with, make SURE you have an empty trap to catch suck back). The remaining contents of the reactor will look like white taffy. The dilute acid in the receiver will look dark brown. The dilute acid in the water trap will be a clear brownish yellow. Once no more acid comes over, you can turn off the heat, take off the water trap, and allow the glassware to cool--slowly. Keep in mind that your glassware is at 400+?C, so donít even think about handling it or taking it out of the mantle or off of the hotplate--the thermal shock will crack the flask instantly. Since you know Argox doesnít make this shit up (unlike others, nameless for now), this means that he found out the hard way about thermal shock and cracking glassware, and is saving you a lot of grief with these words of wisdom.
5. Redistill HI(aq)
There are two ways of telling if your acid is 57%:
1) Weigh it in a graduated cylinder--the density of 57% acid is 1.7. 500 cc will weigh 850 grams, exactly. Anything less is not 57%.
2) Boil it. 57% hydriodic acid boils at 125-127?C.
(OK. OK. Get back on your chair. I was just kidding to see if you were awake. A little black humor--of course you donít fucking boil it, it will corrode everything in your lab including your lungs, just weigh it.)
Probably none of the initial acid collected in either of the receivers is going to be 57%. Weigh it to find out. If its density is less than 1.7, then you must redistill. No sweat. There is a short cut that makes this a snap.
The redistillation is a straitforward atmospheric distillation. No gas will be generated. As soon as the acid boils and starts coming over you must watch the thermometer at the still head. As soon as it reaches 125?, change receivers. Everything that comes over from that point forward is 57% HI(aq). The very last drop will distill out of the boiling flask. No residue will be left, it all boils. In fact, after you have done this distillation once, you will quickly figure out the obvious short cut--collect the fraction that comes over at less than 127?, and then turn off the heat and everything left in your boiling flask is 57% HI(aq), no need to distill it--itís already pure. Just allow it to cool before you package it up.
6. Hypothetical considerations
What follows is the only speculative part of this write-up. You might call this Argoxí version of made-up bullshit. However, even my bullshit should be instructive.
How might the public view hypothetical shop-made HI(aq)? (It depends on their intelligence, of course.) See, acid made by the method I have just detailed is dirty brown. This is due to trace amounts of HI being oxidized to I2 as it comes over in the condenser (4HI + O2 = 2I2 + 2H2O) and from impurities in the tech grade KI. The brown color is insignificant, and does not interfere with the potency of shop-made acid. Commercial HI(aq) contains a reducing agent as a stabilizer, usually hypophosphorous acid, and is clear yellow. In the hypothetical case you use this write-up for other than purely theoretical considerations, at some point the topic of off color might arise. But, again, speaking hypothetically, I would recommend that you educate rather than stabilize. Unstabilized shop-made HI(aq) will work just as well as the store-bought variety in a hypothetical userís hypothetical application. The difference is purely cosmetic. The way to convert dirty brown acid into clear yellow acid is to add red phosphorous and heat it. But hey! Wait a minute! Isnít that what a hypothetical user might be doing anyway? Adding RP and heating it? Explain this to whomever, hypothetically. Give whoever a demonstration in a test tube. Convince them. Hypothetically.
Once the hypothetical user overcomes his or her initial reluctance, donít be surprised with the heavy pounding on the door late one night--no, itís not the cops, it might be that hypothetical person begging for more hypothetical acid. The word might hypothetically spread to others, and the all-request line become incessant. Of course, I really wouldnít know anything about any of this...itís all just hypothetical. I am making it up, OK.
As for packaging, hypothetically pour acid into amber glass bottles, or better yet, the red .....oh shit, since this is all hypothetical, I wouldnít want to be hypothetically linked to a certain bottle...hell, if you are intelligent enough to make acid, you can figure out in what to put it. Remember--one liter of HI(aq) weighs exactly 1,700 grams. In the hypothetical case the hypothetical user goes into a production frenzy and needs volume, think black HDPE jerrycans.
HI(aq) must be protected against light and always stored in a cool (temperature and otherwise cool) area AWAY from people. I wouldnít freeze it, but since Iíve never frozen any, I couldnít really say what might happen. The acid will slowly degrade over time, but no big deal. Without a stabilizing agent, HI will slowly revert to I2. But like I said, no problem: the hypothetical userís hypothetical application will solve that hypothetical problem.
With your native intelligence, youíll figure out all sorts of other shortcuts and useful procedures in the off-chance you actually paid attention and hypothetically decide to make a little hypothetical acid.
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