Baking soda PH?

[CyanoMagnet]

Hey guys (and Randy). I have some Arm & Hammer pure baking soda.

I put one teaspoon into a glass of poland spring water (8.4 ph or so) and the ph went down to 8.00.

I put another teaspoon into it and the ph went down to 7.89.

I put a third teaspoon into it and mixed and ph is now 7.84.

Putting a fourth teaspoon ph is same, 7.84

Now I did the same test with my tank water .

Original PH of the tank water is 8.21.

I put one teaspoon of the same baking soda and the PH went down to 7.49.

2nd teaspoon and 3rd teaspoons kept it exactly the same, at 7.49 ph..

I put 3 teaspoons of this stuff in my tank (dissolved ofcourse) and my tank PH went from 8.26 to 8.15 within 30 seconds (90 gallons of net water).

Do you think there is something wrong with the baking soda, my ph meter, or my tank?

Does anything seem odd to you here?

 

[goldenfamaliy]

baking soda will lower the ph, and baked baking soda will raise the ph. Randy has some good articles in the "reef chemistry articles" forum. start here and work your way down. Very good reading.
http://web.archive.org/web/20021127040526/http://www.advancedaquarist.com/issues/nov2002/chem.htm

 

[Randy Holmes-Farley]

Thanks, golden.

Does anything seem odd to you here?

Nope.

Raw baking soda (sodium bicarbonate) is a stronger acid in seawater than in fresh (for reason I'm happy to go into if you want), so the effects are different and can be opposite. It is one of the wonders of chemistry.

Raw baking soda will ALWAYS reduce the pH of normal seawater, at least initially until you possibly blow off the excess CO2 that it causes. This initial effect is pretty small, however. Baked baking soda ALWAYS causes a pH raising effect in normal seawater, because the CO2 is already baked off. This effect can be pretty large.

I detail the exact expected and measured pH effect in this article, as well as that of some other additives, like limewater and hydrochloric acid:

The Relationship Between Alkalinity and pH.
http://www.advancedaquarist.com/issues/may2002/chem.htm

 

[goneawayfarm]

Randy,

I read the article you referenced and have a question. In your table at the bottom referencing the ph changes over time. What was the change in alkalinity over the same periods of time? I apologize in advance if this should be obvious. I was thinking that if I mixed water change water well in advanced and "buffered" it heavily than the drastic swing in ph maybe eliminated but the positive changes in alkalinity would be retained.

 

[Randy Holmes-Farley]

[welcome]

The alkalinity would not change over that experiment. I did not measure it, but there is no mechanism for it to rise or fall in those test solutions, or in any storage container unless there is precipitation of calcium or magnesium carbonate taking place, in which case it may drop.

I'm not sure what you want to accomplish. Most salt mixes have plenty of alkalinity already in them, and I wouldn't typically want to drive it higher.

 

[goneawayfarm]

Thanks for the response. My goal is to get all of my parameters organized if you will, for the next couple of months before I add any corals or more demanding livestock. Therefore I wanted to "play" a little now with differnt ways to affect changes to my environments chemistry since I do not really have much to loose at this point. To that end currently my water parameters are dkh=6,Calcium=300 ppm based on titration of calcium with EDTA after the coprecipitation of magnesium and strontium, SG=1.024, ph=8.2 as mesured with a color test kit. So I am trying to increase Calcium and alkalinity without causing shifts in ph. I did a dose of Kalk a couple of weeks ago just to see the results and it seemed to effect the ph to a greater degree than ca or alk. I have done a 10% water change using Kent marine salt and it has a negligable effect on the Alk/Ca. I would like to see something that would increase my Alk to dKH of 8-9 and my Ca to 420 mg/l. with out swinging my ph.

 

[Randy Holmes-Farley]

Adding calcium chloride and unbaked baking soda should get you where you want to go with minimal pH effects, and as you noted, any excess CO2 can blow off from the system. .

 

[matthewscars]

my ph is normally 7.9 - 8.2. I dose one tablespoon of baking soda a day. I only notice a lowering of the PH for a few minutes. then everything is normal.

Ah well, i have good aeration i guess.

 

[Randy Holmes-Farley]

Yes, that is what I'd expect if you have strong aeration .

 

[CaptiveReefer03]

If I may chime in here I need some help as well. Today and over the last few days I have been trying to balance my water perams back up to par.
Currently my system is running as follows.

pH 8.0
Sal1.026
no2 0
no3 50-100 (water change in process of being made)
po4 0
nh4 0
Cal. 480
Mag 1450
alk 5.25
Kh 15.2
temp between 76-78*

my question is how can my alk and kh be so far out in left feild but my pH be normal? What can I do to reduce this and bring the system back to par in addation to the massive h2o change Im going to do in the am? I dont feed heavy my bio load is min. given my size of system and I filter and clean all the time, plz help as I really would like to start adding corals to the system but do not wish to kill them. Any help would be greatly appriciated and thank you again in advance.

 

[Billybeau1]

I would first be concerned with kh measurement error. This is most likely the cause unless you are dosing somthing you have not listed like pH buffers.

 

[Randy Holmes-Farley]

pH is driven by the alkalinity and the CO2 level in the water. If alkalinity is normal to high and pH is low, then CO2 is excessive.

i show that here:

Low pH: Causes and Cures
http://reefkeeping.com/issues/2004-09/rhf/index.htm

from it:


Figure 1. The relationship between alkalinity and pH for seawater equilibrated with air containing normal and elevated carbon dioxide levels. The green dot shows natural seawater equilibrated with normal air, and the curves reflect the result that would be obtained if the alkalinity were artificially raised or lowered.