PH control and ppms

J

JonCreighton

Well-Known Member
if i take a gallon of RO water and add a gram of nitric acid to it the ppms read basically 0 to 750ppm.

that means 4 grams into a gallon should b ~ 3,000 ppm

working w roughly 100 gallons cycling solution u would think adding 4 grams of nitric acid should increase the ppms of the cycling soultion by roughly 30ppms.

750 ppms * 4 grams = 3,000ppms/ 100 gallons = 30 ppms

this is not how the meter reads.... 4 grams will cause the ec to rise initially (few seconds) but settle back to the original number or maybe just slightly higher as it dissipates thru the system. probable need to add what the math says would be +50ppms to get the ppms up 10 on the meter.

anyone know whats going on here. i seem to having similar issues w sulfic.
 
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jondamon

jondamon

Well-Known Member
JonCreighton said:
if i take a gallon of RO water and add a gram of nitric acid to it the ppms read basically 0 to 750ppm.

that means 4 grams into a gallon should b ~ 3,000 ppm

working w roughly 100 gallons cycling solution u would think adding 4 grams of nitric acid should increase the ppms of the cycling soultion by roughly 30ppms.

750 ppms * 4 grams = 3,000ppms/ 100 gallons = 30 ppms

this is not how the meter reads.... 4 grams will cause the ec to rise initially (few seconds) but settle back to the original number or maybe just slightly higher as it dissipates thru the system. probable need to add what the math says would be +50ppms to get the ppms up 10 on the meter.

anyone know whats going on here. i seem to having similar issues w sulfic.
Click to expand...

RO water has no buffering capacity as it is pretty much void of any minerals.

if you are making a solution that can hold pH you need something there for the pH to stabilise with.

For example.

if you add 0.2EC of calmag to the RO water this gives it some buffering capacity.

then try your pH adjustment as you have been and see what happens.
 
J

JonCreighton

Well-Known Member
im more interested in ppm sums than buffering capacity.

buffering capacity is a different calculation that im not much interest in. i would prefer to hit my ppm targets for nitrogen and phosprus. then u can just add sulfric (within reason) to get to the ph u want to be at cuz sulfuric is kinda the liberal variable in hydroponics. 10-200ppms. so if im not where i want to be ph wise after iv hit my N and P targets ill use the battery acid to make up the difference and get down to 5.6 and just assume im no where near surpassing 200ppms S.

if u want to be at 160 ppm n and 50ppm P
your salt solution is 100ppm N so u would only want to add ~60ppm N from nitric acid
your salt sultion is 30ppm P so u would only want to add ~ 20ppm of ph down

Im confused why the conversion rates from 0ppm ro water recieving acid differ from 500ppm water recieving acid. they seems to have a different effect on ppm reading according to the bluelab meter i got. they are deffinatly not in porpotion atleast. i cant think of any percipatory factors as the acid is added slowly...

iv got 3,000 ppms of nitric acid in a 1 gallon bucket.... i pour the bucket into 100 gallon ccycling solution. math would say ur going to see a ppm increase of 30 ppms on the meter. This is not what happens. meter barley flinches. weird
 
jondamon

jondamon

Well-Known Member
JonCreighton said:
im more interested in ppm sums than buffering capacity.

buffering capacity is a different calculation that im not much interest in. i would prefer to hit my ppm targets for nitrogen and phosprus. then u can just add sulfric (within reason) to get to the ph u want to be at cuz sulfuric is kinda the liberal variable in hydroponics. 10-200ppms. so if im not where i want to be ph wise after iv hit my N and P targets ill use the battery acid to make up the difference and get down to 5.6 and just assume im no where near surpassing 200ppms S.

if u want to be at 160 ppm n and 50ppm P
your salt solution is 100ppm N so u would only want to add ~60ppm N from nitric acid
your salt sultion is 30ppm P so u would only want to add ~ 20ppm of ph down

Im confused why the conversion rates from 0ppm ro water recieving acid differ from 500ppm water recieving acid. they seems to have a different effect on ppm reading according to the bluelab meter i got. they are deffinatly not in porpotion atleast. i cant think of any percipatory factors as the acid is added slowly...

iv got 3,000 ppms of nitric acid in a 1 gallon bucket.... i pour the bucket into 100 gallon ccycling solution. math would say ur going to see a ppm increase of 30 ppms on the meter. This is not what happens. meter barley flinches. weird
Click to expand...
Right ok. At this point my honest answer is I don’t know lol.

but I think I know someone who can converse with you possibly on this topic.

@xtsho anything here that’s up your street?
 
xtsho

xtsho

Well-Known Member
jondamon said:
Right ok. At this point my honest answer is I don’t know lol.

but I think I know someone who can converse with you possibly on this topic.

@xtsho anything here that’s up your street?
Click to expand...
I'm not versed in this topic. I've never used RO water so I've never taken the time to understand it's properties.
 
J

JonCreighton

Well-Known Member
its weird.

there is math out there that would tell me how to get lets say 50 ppms of nitrogen from 67% nitric acid. i should do that math and see if it matches the testing numbers. idk how at the moment tho.

the way i do it is i get the fertalizer and i test its ppm in 1 gallon RO water to 1 gram fertalizer. if its 500 ppms ill just work the math backwards and get the NPK ppm percentages that way. it works fine for salt fertalizers. it doesnt seem to work with the ph control acids.
 
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