Changing salt, the new salt is 1.5dkh higher than my old salt, if I were to start running my tank at the higher alk would the ph boost from 7dkh to 8.5 be significant or marginal at best? Thanks.
Alk increase affect on ph?
- Thread starter Reef.
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About 0.08 pH units if everything else is the same.
@Randy Holmes-Farley How do you make that calc? Based on my equations with indoor CO2 at 600, I get 0.06 change.
You calculation is likely more accurate if you use something like equation 2 from this article:
Chemistry And The Aquarium: The Relationship Between Alkalinity And pH
Randy answers many questions in this complex relationship.
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I just used the first term from eq 2 and ignored the second one for this estimate.
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I'm using the CO2Sys model written in Python.You calculation is likely more accurate if you use something like equation 2 from this article:
Chemistry And The Aquarium: The Relationship Between Alkalinity And pH
Randy answers many questions in this complex relationship.
I just used the first term from eq 2 and ignored the second one for this estimate. The bigger the pH change, the more error in my estimate. Thought of differently, term 1 makes the pH and alk linearly related, but as can be seen from the graph, the line actually curves due to the second term, making my estimate an overestimate.
Ok. I was concerned that my calculations has been off...now I feel better.Then I expect yours is the more accurate number.
OK, you inspired me to download an xl version of Co2sys.
Using a pCO2 of 400 and 25 deg C, I got a pH difference of 0.0704
Using a pCO2 of 600 and 25 deg C I got a pH difference of 0.0731
So I'm now not sure why you got a slightly different value. Maybe your program uses different constants or makes different assumptions.
Using a pCO2 of 400 and 25 deg C, I got a pH difference of 0.0704
Using a pCO2 of 600 and 25 deg C I got a pH difference of 0.0731
So I'm now not sure why you got a slightly different value. Maybe your program uses different constants or makes different assumptions.
par1type = 1 # The first parameter supplied is of type "1", which means "alkalinity"; type "4" which means Seawater partial pressure of CO2; 8" which means "Aqueous CO2""; "9", which is "Dry mole fraction of CO2""
alk = 8.5
par1 = alk*1000*0.36 # value of the first parameter
print("Tank measured Alk =", alk, "dKH (", par1, ")")
[HASH=74894]#par1[/HASH] = 1500
[HASH=23882]#print([/HASH]"Tank target CO2 =", par1, "matm ")
par2type = 9 # The second parameter supplied is of type "3", which means "pH"; type "4" which means Seawater partial pressure of CO2; 8" which means "Aqueous CO2""; "9", which is "Dry mole fraction of CO2""
# par2 = 7.73 # value of the second parameter
# print("Tank measured pH =", par2, "NBS")
par2 = 600
print("Air CO2 =", par2, "ppm")
sal = 35 # Salinity of the sample
tempin = 25 # Temperature at input conditions
tempout = 25 # Temperature at output conditions
presin = 0 # Pressure at input conditions
presout = 0 # Pressure at output conditions
sil = 50 # Concentration of silicate in the sample (in umol/kg)
po4 = 2 # Concentration of phosphate in the sample (in umol/kg)
pHscale = 4 # pH scale at which the input pH is reported ("1" means "Total Scale") ("3" means Free Scale)("4" means NBS)
k1k2c = 4 # Choice of H2CO3 and HCO3- dissociation constants K1 and K2 ("4" means "Mehrbach refit")
kso4c = 1 # Choice of HSO4- dissociation constants KSO4 ("1" means "Dickson")
I'm curious if @Randy Holmes-Farley can see why we get slightly different answers...
I don’t see an obvious difference, but I didn’t look into the actual values of the various constants used.
I’ll post the link I used if you want to compare it.
I’ll post the link I used if you want to compare it.
Sure...that would be great.
I’ll post it in the AM when I’m on my computer.
Sound good.
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