water PH

[papheteer]

7 is fine.

What is the normality (or molarity) or your acid? Drops is a pretty meaningless unit without either knowing the stock concentration or the final P concentration in your irrigation water. You probably should try to hold final P to 1-5 ppm.

There's probably a good aquarium test kit available for that. I use Hach tests at work and the P test is a simple powder pillow with an indicator that turns shades of blue based on concentration.

You are right. All i know is the phosphoric acid i use is 85%. I will try and look for a test kit. Thanks again.

 

[papheteer]

Searched online and found out that 85% phosphoric acid is 51% phosphorus. I used Ray's ppm calculator and it says i need .01 tsp/gallon of the phosphoric acid to give me 3 ppm of P. Now to figure out how many drops in an ml. Sorry for my primitive math.

 

[Ray]

Had you scrolled a bit farther down my "Free Info" page from the calculator links, you'd see the one for conversion factors, telling you that a milliliter is 15.42 standard water drops.

 

[papheteer]

Thanks, Ray. I did see that. But i assumed that every dropper and liquids are different so i tried to measure. Used a 1/8 tsp measuring spoon and took 22 drops from the eye dropper that i use to fill it up.

 

[papheteer]

So if my math is right, it would take 2 drops (from my dropper) of phosphoric acid per gallon of water to achieve 3 ppm P.

 

[ALToronto]

Thanks, Ray. I did see that. But i assumed that every dropper and liquids are different so i tried to measure. Used a 1/8 tsp measuring spoon and took 22 drops from the eye dropper that i use to fill it up.

That doesn't sound right. Are you sure it was 1/8 tsp? Even 1/8 tbsp would take less than 22 drops. I can see acetone or even pure alcohol having really tiny drops compared to water, but 85% phosphoric acid should be heavier than water, hence more surface tension and bigger drops. Are you letting each drop form and fall under its own weight?

 

[Stone]

For the kelp, is it ok to use it every watering?

Kelpac recommends no more than every 10 days so the plant can complete its root initiation and start its growth cycle. Every 2 weeks is probably fine.

 

[papheteer]

That doesn't sound right. Are you sure it was 1/8 tsp? Even 1/8 tbsp would take less than 22 drops. I can see acetone or even pure alcohol having really tiny drops compared to water, but 85% phosphoric acid should be heavier than water, hence more surface tension and bigger drops. Are you letting each drop form and fall under its own weight?

Yup i used a 1/8 tsp. I also used an eye dropper. I did let each drop form.

 

[Rick]

But i assumed that every dropper and liquids are different so i tried to measure.

The only thing that really dictates the size of a drop is the viscosity of the fluid (not the dropper configuration).
For something the viscosity of water its 20 drops per ml.

Phosphoric acid is a little more syrupy, so I can see 15 drops per ml

 

[Rick]

Yup i used a 1/8 tsp. I also used an eye dropper. I did let each drop form.

A full tsp is 5 ml hence a 1/8 tsp should be 0.625ml (and 12-13 drops of water)

When I used your 0.01ml of acid/gal I came out with just shy of 1 drop/gal to get that 3 ppm

 

[papheteer]

A full tsp is 5 ml hence a 1/8 tsp should be 0.625ml (and 12-13 drops of water)

When I used your 0.01ml of acid/gal I came out with just shy of 1 drop/gal to get that 3 ppm

I did try again today. Used a plastic pipette and it took about 12 drops of phosphoric acid to fill 1/8 tsp. Then I tried my dropper again (an empty eye drops bottle) and the drops are somewhat smaller and it took 23 drops to fill 1/8 tsp.

 

[Rick]

I did try again today. Used a plastic pipette and it took about 12 drops of phosphoric acid to fill 1/8 tsp. Then I tried my dropper again (an empty eye drops bottle) and the drops are somewhat smaller and it took 23 drops to fill 1/8 tsp.

Weird Maybe the eye dropper is forcing the drops to fall before full gravity base drop formation.

I'd use the plastic pipette in this case since its closer to convention.

 

[Trithor]

I would imagine that it is not only surface tension that plays a roll under these circumstances, but the 'cohesive' forces between the tip of the dropper and the fluid being dropped. My memory of physics and chem at varsity tells me that should not be true, but my gut tells me that there should be an influence.