Problems with Mel Frank's ppm calculations

[JesseGreenman]

I was recently trying to introduce a new nute compound into my hydro system, and was calculating amounts needed. Anyway, I started with amu's in the Periodic Table to source weight info to arrive at my ppm results, and when I compared my results to Mel Frank's in 'Marijuana Grower's Insider Guide' they were way off.

For example, in the book, for potassium nitrate (KNO3), he suggests 0.044 oz./100 gallons = 1 ppm of potassium (K)

When I do my math, I get 0.0344 oz. KNO3/100 gallons = 1 ppm K

I got to this number assuming he was dealing with US gallons, so I tried using Imperial gallons, and while still off (0.4146 oz. KNO3/100 Imp. Gals. = 1 ppm K), it was much closer, as it was when it came to the nitrate (N) numbers.

So I isolated the coefficient needed to arrive at his number for K, and it was 4.824 liters for the 'gallon'.

Here's the weird thing: when I plugged this co-efficient to other nutrient compounds he lists in the book, and made my own calculations starting at the Periodic Table, both our numbers jive perfectly.

WTF???


Update: I found that the 4.824 factor didn't work on other compounds... back to the drawing board.

Are there any actual chemists on this site? Any help would be mucho appreciado... thanks...

 

[LEDBud]

Use a ppm meter

 

[JesseGreenman]

Use a ppm meter

OK, again, Mel Frank, in his book, gives a certain mix ratio to achieve certain ppm levels in the nutrient solution.

According to actual atomic weight of nutrient elements involved however, the amounts given by Frank to achieve the required ppm levels is wrong.

So, are his mixing recipe values wrong?


Or are his table of recommended ppm of nutrient in solution wrong?

 

[LEDBud]

You need to invest in a cheap ppm meter or a good one your choice

I will add and forget about trying to do it by atomic weight as stated on the periodic table.

But don't let me stop you from wasting your time cross examining books to mathematic formulas that no one in today's age of meters cares about.

My suggestion is to use a ppm meter to accomplish the correct ppm , if you want compare its readings to mel franks book.

I myself find the idea of using a meager as it gets 1 ppm as useless.

Maybe Mel mixed up the numbers ... He is a pot head or maybe you read or wrote it wrong.


Something is fishy with the 1 ppm you see people usually use a all nutrients combined 800 or 1400 ppm varying to their style.

1 ppm is NEVER used for a nutrients strength never

Ever

This forum has much up to date info on it , My first grow book 30 years ago was Mels growers handbook I have since learned 100x more information from the web and plenty on this site

quick edit

 

[Spitz]

Chem Engr here... I'll point you in the direction if you want to go there, but I must ask why? You could run all the math in the world but the accuracy of your scale, variance of volume H2O with temperature and ability to measure, and impurities in your starting material would give far, far, far more error than just grabbing a $7 PH pen. Humor me... wtf would you want to put yourself through this for? There is no factor that works for more than one compound. PPM is just milligrams of solvent/liter of water. 1mg of KNO3 in 1 Liter of water is 1 ppm of KNO3. Just remember you have 1 part K for every part of NO3. You'll have to break it down by molecular weight to find out your share of k in total by mass. Pretty good stoner chemistry question, but geesh. Just buy a pen.. lol

Sorry, your post made me smile. Well, I read your OP 4 times and still am not sure what your question is. If it is "what is the coefficient", the answer is "it's different for every compound based on molecular weight of each element in the compound". Good luck with this one!


Edit. after 3 years of Organic Chemistry, it turns out I have no idea what "organic" is. I think it's just a sticker, but I'm still searching

 

[JesseGreenman]

Spitz:

The question is, how did Frank arrive at his values in his mixing ratio tables, which are apparently incorrect? (According to my calcs., that is.) He uses non-metric values (just says gallons and ounces) yet when broken down using metric, the numbers don't jive. So what's wrong here, his coefficients, or the recommended nutrition levels themselves?

In short I am trying to get to the bottom of this discrepancy.

Now, you find humor in my OP, fine. But let me ask you, what would a ph meter have to do with dissolved solids in a solution, other than the acid/base levels introduced? Also, you ARE just joking about not knowing what "organic" is, right?

 

[Spitz]

K=39
N=14
O=16 (x3 =48)

Total mass=101
39/101 = 0.386

As mentioned, 1ppm = 1mg of solute per Liter of water. Dissolve 1mg of KNO3 in 1L of water and you have .39ppm of potassium.

If you need help with basic conversions, just ask again. Sorry, I didn't want to offend the OP.

 

[Spitz]

Spitz:

The question is, how did Frank arrive at his values in his mixing ratio tables, which are apparently incorrect? (According to my calcs., that is.) He uses non-metric values (just says gallons and ounces) yet when broken down using metric, the numbers don't jive. So what's wrong here, his coefficients, or the recommended nutrition levels themselves?

In short I am trying to get to the bottom of this discrepancy.

Now, you find humor in my OP, fine. But let me ask you, what would a ph meter have to do with dissolved solids in a solution, other than the acid/base levels introduced? Also, you ARE just joking about not knowing what "organic" is, right?

I'm not kidding about organic at all. One can have two identical substances and one is organic while one is not. Again, I believe it's a sticker/stamp that can be purchased. As for how Frank arrived at his answer, you need to have Frank answer that. I don't own the book you are referring to. PM me a picture of the page and I can check his work if you want. If you want me to find a specific concentration, just ask and I can do it.

I asked why you are trying to figure this out. Contrary to what Kellen thinks, I was quite interested in what you were really trying to do. I doubt you're just trying to prove some author wrong. There is something deeper I suspect and the only thing I can think of is a commercial type application (big commercial application). A PH pen is obviously not going to tell you anything regarding ppm. A salinity pen is what you're after.

 

[Saibot]

I get the frustration on both sides. It's the analytical mind/practical mind thing. They don't really play well together, do they.