# Fertilator & Pharmaceutical Grade Chemicals



## nasfish (Sep 26, 2005)

Hi,

I am not sure if this question have been asked before or not. Searching through the forum gives me various feedbacks...no direct answers

Questions:
1. Is Fertilator based on agricultural grade chemicals?
2. If so, how to make a solution of pharmaceutical grade chemicals using the the Fertilator?

FYI, I have KH2PO4, pharmaceutical grade PO4-Phosphate 69.8% and agricultural grade PO4-Phosphate 23.3%. I am making PO4 solution.

Please don't ask me why should I use the pharmaceutical grade chemicals..no other intentions here..

Thanks 

Regards


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## Tonka (Mar 20, 2004)

This is a very interesting question. The Fertilator must assume that all chemicals are 100% pure. There is no one specific "agricultural grade" assay. There are many or few, depending on the chemical and the supplier.


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## Squawkbert (Jan 3, 2007)

I'd be interested to know what the ag. grade stuff is cut with.


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## hoppycalif (Apr 7, 2005)

This is a very interesting question. I think we all have been assuming that if we buy KH2PO4, for example, we are getting a powder that is more than 90% KH2PO4. The question makes me wonder if that is really the case. A 10% error when calculating how much PO4 we are adding isn't relevant, but the much larger errors inherent in your question sure are. How do you find out what the purity of agricultural or pharmaceutical grade substances is? And, as Squawkbert asked, what are the impurities?


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## dennis (Mar 1, 2004)

If you're buying pharm. grade it will state somewhere its purity; which you obviously saw and know. The only way to be sure is to figure out the math based on your particular substance, and compare that to what Fertilator tells you.

Wait, ag grade PO4 is only 23.3% pure? Pharm grade only 69.8%?!!!!

That aside, lets pretend what you have is 69.8% pure. That means that 1gram of your substance actually contains 0.698 KH2PO4, or 698mg PO4.

The molecular weight of KH2PO4 is:
K=39.0983g/mol
H=1.0079*2=2.0158g/mol
P=30.9738g/mol
O=15.9995*4=63.998g/mol
Total= 136.09g/mol
PO4= 94.97

So PO4= 94.97/136.09=.698 or 69.8%...... what, thats exactly what they claim pharm grade is. So... I would assume (hopefully that does not make me an ass) that the 69.8% assay they claim is the actual PO4-Phosphate assay. That is all that really makes sense. Therefor, we can assume that your pharm grade KH2PO4 is basically pure, by aquarium standards at least.

Try this again, PO4 is 69.8% of KH2PO4 so 1 gram of KH2PO4 contains 0.698g of PO4. There are 1000mg in a gram so there are 698mg PO4 in 1 gram of KH2PO4. For ease of thought, if we add 1gram of KH2PO4 to 1liter of water, then we have 698mg/l.

Now what does the Fertilator give us for those numbers: 697.9mg/l PO4

Perfect!

So what does this mean for ag grade stuff? Assuming the same things as before, 1g of ag grade KH2PO4 has .233g, or 233mg/g PO4 sonce it is 23.3% PO4. That is a difference of a factor of 3 between ag grade and pharm grade. Therefor, in theory one would need to use 3 times as much ag grade as the Fertilator says, providing your numbers for ag grade is correct. I have no idea as to that.

Interesting....


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## MrSanders (Mar 5, 2006)

hmmmm... intresting stuff. So assuming that those numbers are correct for ag. grade chemicals (and again as dennis said, hope im not making an ass of my self for doing so) those of us using them would in theory be actually adding 1/3 the amount that we thought we were based on fertilator calculations.... thats a pretty big difference...

Anyone know what it is greg sells? and a way to know what the actual % of purity it has?


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## dennis (Mar 1, 2004)

Emailing Greg would be one way to go. He states that his chemicals are ag grade, so its not like he's trying to fleece us. The purity may be listed on the bags he gets. In truth, given the levels we tend to run in our aquariums for nutrients, it may make no difference in the end, especially with EI. Still, its an interesting thing to ponder or be aware of.

The Fertilator should assume 100% purity and is programed by molecular weights.


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## turbomkt (Mar 31, 2004)

The info on my Ag grade KH2PO4 doesn't measure PO4. The analysis shows as 0-51-33 which is:


> Available Phosphoric Acid (P2O5)......51%
> Soluble Potash (K20)......................33%
> 
> Derived from: Monopotassium Phosphate


I'm not sure how that changes when talking PO4.


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## nasfish (Sep 26, 2005)

Hi guys, 

Getting interesting, thank you..

I am waiting for a reply from the guy supplying/selling this chemicals about how did he know the purity of agricultural or pharmaceutical grade chemicals is..

Anyway I am still got no idea to make my PO4 stock solotion..lol..but the guy just told me something like this..

1. KH2PO4 Pharmaceutical grade PO4-Phosphate 69.8% 
7 gram in 500ml RO water solution will give you 0.49ppm for each 1ml
solution in 20L water. 

2. KH2PO4 Agricultural grade PO4-Phosphate 23.3% 
21 gram in 500ml RO water solution will give you 0.49ppm for each 1ml
solution in 20L water. 

I am not sure if this is correct..but using the Fertilator, I get a correct answer for KH2PO4 pharmaceutical grade PO4-Phosphate 69.8%...

I do not know what this mean, but I am getting confused here..have been using agricultural grade chemicals for years..

Regards


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## nasfish (Sep 26, 2005)

Found an old post here while searching the forum, maybe can tell what are the impurities can be..

Regards


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## dennis (Mar 1, 2004)

Nasfish, he is saying to use 3 times as much ag grade. This makes sense from the numbers if it is based on actual %PO4 in the substance.

How he figures it:
7grams= 7000mg*.698= 4886mg of PO4 are added to 500ml H2O. Se, 1 ml of that is 4886/500= 9.772mg of PO4. If you add that to 20 liters, 9.772/20= 0.4886mg/l of PO4. mg/l and ppm is the same thing. This is what the Fertilator does for you, giving you an answer in PO4 you are adding.

Mike, I will have to look up how they measure that. In order to standardize fertilizers, the US requires that all compounds be listed _as if_ they were supplied by the same thing. P is always measured in terms of P2O5, K as K2O, etc. This is similar to how we measure Gh of water as CaCO3 when only some, or maybe even none, of the hardness actually comes from that source. I need to look back through my Soils notes to find how to convert it.


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## nasfish (Sep 26, 2005)

Thank you dennis, I never good at math, but you are making it easier..

So it is true then, the Fertilator is assuming 100% purity?..

Regards


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## dennis (Mar 1, 2004)

Ok, using mol mass again... P2O5 is 44% P elemental, your 51% is 51*.44=22.44% actual P elemental by weight. Compare that to pure KH2PO4 which is (30.97/136.09)*100= 22.8% P elemental by weight. That is a difference of only 0.4% so nothing I would worry about.

To consider %P in terms of PO4, we just learned that pure KH2PO4 is 69.8% PO4 and pure KH2PO4 is 22.8% P 69.8/22.8= 3.06 SO if we use 3.06 as a conversion factor and test that against our pure KH2PO4 with 22.8% P elemental, 22.8*3.06= 69.8% as PO4. So, you ag grade stuff at 22.44%P*3.06= 68.7% as PO4.

What you have Mike is pretty pure. I am actually surprised at that purity for ag grade! I wonder if I am doing something wrong?


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## turbomkt (Mar 31, 2004)

I have no idea if you're doing anything wrong. It's been 15 years since I took chemistry in college, so I'm not in the mood to relearn a whole lot of stuff atm.


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## dennis (Mar 1, 2004)

Reading though Nasfish's link, I do want to remind about something.... I am more than willing to email Greg Watson to see if he can read the assay from the bags he uses. I don't want this to turn into a "what are you people trying to sell us" thing. Also, I assume nasfish is not getting ferts from Greg Watson but I know many who read this may be so I wan to re-itterate, he lists directly on his site that what he sells is ag grade. My curiousity regarding the purity is simply for my own obsessive tendencies and has nothing to do with thinking that ag grade is bad. My biggest question is simply so I can make exact doses if I so choose, not because I think these chemicals are dangerous for their impurity.


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## nasfish (Sep 26, 2005)

No, I am not getting ferts from Greg Watson, I am from the other part of the world hehehhe...I also stated earlier in my first post, no other intentions. Just want to know how to make my PO4 stock solution using two different grade of chemicals..using the Fertilator..

One thing though the guy actually says it is horticulture grade, is it the same as agriculture grade?. Pardon for my english..lol..not good at it..

Regards


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## dennis (Mar 1, 2004)

It would most likely be the same thing, just a translation error. While here we tend to think of agriculture as farming and horticulture as growing pretty things, it is highly unlikely that one would be different than another


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## hoppycalif (Apr 7, 2005)

dennis said:


> Ok, using mol mass again... P2O5 is 44% P elemental, your 51% is 51*.44=22.44% actual P elemental by weight. Compare that to pure KH2PO4 which is (30.97/136.09)*100= 22.8% P elemental by weight. That is a difference of only 0.4% so nothing I would worry about.
> 
> To consider %P in terms of PO4, we just learned that pure KH2PO4 is 69.8% PO4 and pure KH2PO4 is 22.8% P 69.8/22.8= 3.06 SO if we use 3.06 as a conversion factor and test that against our pure KH2PO4 with 22.8% P elemental, 22.8*3.06= 69.8% as PO4. So, you ag grade stuff at 22.44%P*3.06= 68.7% as PO4.
> 
> What you have Mike is pretty pure. I am actually surprised at that purity for ag grade! I wonder if I am doing something wrong?


Dennis, my head is swimming with all of those calculations, but aren't you saying the two percentages, 23% and 69%, or whatever they were, are apples and oranges? One is percent of PO4 and the other is percent of P? As I said, I am confused. But, I think we are eventually going to arrive at the conclusion that agricultural grade KH2PO4 is in the ballpark of 90% pure, vs. nearer to 100% pure for chemistry lab stuff. If I am right, I don't see a reason for me to be concerned at all - my measurements of ferts is about +/- 33% anyway.


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## dennis (Mar 1, 2004)

That is sort of what I am saying. What Mike posted seems very pure. What nasfish is posting is not very pure at all, by a factor of 3. 

If I have done the math correct, Mike's is 68.7% PO4 or 98.7% pure. Nasfish has been told that his ag grade stuff is 23.3%PO4 or 33.4% pure. Big difference there, though that difference leads me to believe there is an error somewhere, either in my math or nasfish's supplier. Maybe the fact the nasfish is in Malaysia makes a difference but I do not know. Here, ag grade can be any number of different things and Mike may be lucky to get it as monopotassium phosphate rather than rock phosphate or some other random mix of P sources.


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## nasfish (Sep 26, 2005)

Hi,

I am still waiting a reply from my "not going to be" supplier, on the KH2PO4, to verify the purity of his chemicals.. Luckily I am in the process of buying it though lol...previously I got it from somewhere else..works fine for me..

So actually how many grade of agricultural fertilizers are out there? Just wondering :?

Regards


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## dennis (Mar 1, 2004)

It is hard to say how many different grades there are. This may also vary some by country, I do not know. I would be interested to know what your "supplier" says and if his response is typical for Malaysia.

It would seem that in the US things are a little more standard but I am not sure of that either. One thing I do know, (and this does not really help you much nasfish but I think there may be others following this thread who would benefit so please excuse the brief hijack) I checked the labels on the potassium nitrate and monopotassium phosphate the Greg Watson sells. While they are ag grade, the purity is high enough to make no difference. The labels, which are required in the US by law, indicate that both of those substances have a purity of 97-99%, as did the stuff Mike posted about. This does not cover every product sold in the US, but the stuff the Greg has at this time is very high quality.


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## hoppycalif (Apr 7, 2005)

I think KH2PO4 and KNO3, like Greg sells, are intended for hydroponic growers, not for regular agricultural use. Regular agricultural fertilizers are almost always diluted, but there is no reason for hydroponic ferts to be diluted.


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## dennis (Mar 1, 2004)

That I don't know. You'd have to ask Greg. All I know is the labels read exactly like the example Mike posted, though all fert in the US, regardless of its intended use must display concentrations in that fashion. Regardless of what they are for, his stuff is, for our purposes, pure enough.


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## nasfish (Sep 26, 2005)

Hi,

I am so sorry if this thread making some people uncomfortable. I wish I could buy dry ferts from Greg too!!!..

I am still waiting for a reply. :heh: It is a weekend anyway since this thread started..maybe today or tommorow, I will get the response..

Anyway, I think the guy is making a mistake, maybe 23.3% is the percentage of P in KH2PO4 while 69.8% is the percentage of PO4 in KH2PO4. I am not sure though. I think, most of the agriculture chemicals in this country, Malaysia, are imported. So, there should be no difference. 

Regards


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## BryceM (Nov 6, 2005)

I think the explanation here is probably a simple one. Most likely it's one of labeling (P vs PO4 as expained above). Rest assured that what we've all been using is just fine. Nasfish, many of the chemicals we have in the US come from Asia and South America - probalby a lot closer to you than to us.

My understanding of the manufacture and sale of dry chemicals is that for our purposes the grade makes almost no difference. ACS grade is the highest, followed by reagent grade, lab grade, pure, technical, and finally agricultural grade. For all but the last one or two, purity is on the order of 99% or higher.

I'm certain that the "agricultural grade" KNO3 and KH2PO4 used by us in our tanks is no worse than 90 or 95% pure. Most likely it's on the order of 98% which seems to be usual for technical grade. These aren't the most difficult chemicals to produce on a large scale. There aren't any additional savings to be had to go looking for chemicals with lower purity either.

Next time you look at your bag of ferts take a close look. Most of it is probalby in the form of very uniform crystals. There's always a few flakes of random debris but the actual quantitiy of this is very small.


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## Rex Grigg (Jan 22, 2004)

And this whole discussion is a bucket of hogwash.

Agricultural grade in most all nutrients is 99% pure. Or even 99.9% in many cases. Pharmaceutical grade is going to be 99.999% pure. And those extra nines cost you a ton of money.

Pay no attention to the stupid government required labels on bags of fertilizers. They actually mean nothing and a lot depending on how you look at it. They mean nothing about the "grade" or "purity" of the product. But mean a lot when it comes to telling someone who knows how much of a certain ion the product will deliver to the soil.

It's the old FUD (fear, uncertainty and doubt) syndrome. People run around talking about impurities yet never give any concrete proof. Talk is cheap.


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## dennis (Mar 1, 2004)

Rex, why are you bashing this? A guy in Malaysia was providing numbers that seems very different than we would see. I was trying to use this post to help him and also to reassure people here in the US that they have nothing to worry about. I was trying to staunch you FUD by showing that the US ag grade stuff is as pure as you say. No one is saying anything about impurities here except that there are not really any in the US.


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## Squawkbert (Jan 3, 2007)

Rex Grigg said:


> And this whole discussion is a bucket of hogwash.
> 
> Agricultural grade in most all nutrients is 99% pure. Or even 99.9% in many cases. Pharmaceutical grade is going to be 99.999% pure. And those extra nines cost you a ton of money.
> 
> ...


I agree and was about to post the same idea. If it's a dry ~white powder, it's at least 95% (if not 99+%) pure. Lab grade chemicals are purified further because having a couple of 1/10ths of something else in a lab buffer can ruin someone's day, depending on the application. Purification to lab grade frequently means multiple recrystallization setps, each of which typically lowers your yield (you have to throw out about 10 good for every bad).

Plants are not as picky, so ferts are <ACS grade in most cases. This means they're priced in the $/100# bag range instead of the $/gram range.

The discrepency has to be a function of reporting one compound in terms of equivalents of another (PO4 in terms of P2O5, for example). If someone not so lazy as me wants to take the time, I suggest that they compare the formula weight ratios of PO4 vs 1/2 the formula weight of P2O5. The difference is probably there (I don't know why I was thinking it might have been cut unless I thought it may have been a poorly labeled all-in one fert w/ K, N, and P).


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## nasfish (Sep 26, 2005)

Firstly, I am sorry if this whole discussion is a bucket of hogwash as Rex put it. But through this discussion, I found out and learned that :

1. The Fertilator is assuming 100% purity and is programmed by molecular weights. Thank you, dennis.
2. Whatever grades are, the different is insignificant for our purposes. The impurities do not matter. No proof.
3. To calculate manually, how many ppm of PO4 if I were to add certain amount of KH2PO4 without using the fertilator. And I never good at math. Thank you again, dennis.
4. Not to trust entirely when someone come up with a different numbers. That is what I am doing, to find out the truth.
5. Use and continue to use what works for you before. So, I am back to the original source of fertilizer.
6. Lastly, when talking about fertilization, people tend to get a bit emotional ..hahahaha...


Thank you to all, esp. dennis, have been a great help. I got what I am looking for. As someone said, the only dummy questions are those that are not asked. No fun to be here too...being here means, got problems to solve. 

End of story.


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## hoppycalif (Apr 7, 2005)

nasfish, this was a very interesting discussion, even if it did end up with the conclusion that we don't have a problem buying dry fertilizers. I think it is a good idea to discuss basics like this every few months. How else will we get to rethink our assumptions?

One last comment: occasionally someone will ask about using fertilizer from their garden shop - one that has numbers like 10-10-8 on the side of the package. I hope we all realize that none of this discussion was about that kind of fertilizer. We were only discussing "pure" chemicals, not "fertilizer" sold for terrrestrial plants.


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## dennis (Mar 1, 2004)

Your welcome nasfish.


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