pH Adjustment of Small Water Sample

[amlez]

I know I'm not Robinson Crusoe, but I don't have a great deal of confidence in my interpretation of my pH test results ( I use the Aussie CCL test kit which I believe is similar to the Taylors one used widely in the States?).
The colour scale ranges from yellowy/orange hue at the low end (6.8) , to pinky/red at the 'high' end (7.8).

Now, as much as I'd like to call 7.6, I'm thinking my pH sits in the 8+ range in reality.

Problem is, while I know it's more than 7.2, from 7.4 up on the colour scale, they all appear pink/purple?? to me, but none of them actually match the colour of my sample, which seems a much 'deeper' colour (I wish the colour scale went to 8/8.2 !!). When I say 'deeper' colour, it's a richer colour, but not necessarily pinker or redder?? (Hope I'm explaining myself properly here??).
I test the standard, and I see the 7.2 as it clearly has an orange tinge to it.

What I'd like to be able to do is test the water, get the same reading I always get (7.6 - 8.2 ??? somewhere), then incrementally add a small amount of acid & retest to see the gradual effect on the viewing tube scale - I'm sure this will help me understand which range my normal test sits in.

Does this sound feasible?? - and if so,
1/. How much acid ( I use Hydrochloric Acid) would I need to add to a 500ml (17floz?) sample to reduce pH by .1 or .2 ?? (I envisage using a pipette).
2/. As I don't particularly want to be playing around with dripping Hydrochloric Acid, would I get the same result using vinegar, lemon juice, or some other form of less 'nasty' acid??

Just by the by, I'm adding 500ml of HCL Acid weekly, and the pH reading doesn't ever seem to change (TA also sits fairly steadily in the 75-100 range)

 

[ajw22]

It may be easier to look into PH Meters

 

[mknauss]

Try using one less drop of reagent in your test. I find it makes color matching easier. Also use a white background in bright sun.

 

[amlez]

Try using one less drop of reagent in your test. I find it makes color matching easier. Also use a white background in bright sun.

Yeah - tried all the white background, cut-out on white cardboard, etc stuff - and it doesn't help much. The water sample color never seems to match any colors on the viewing tube chart (it's as if the the colours on the viewing tube are 'faded'). The CCL test says x2 drops of reagent - so you're saying just use 1 drop? (this may make sense as maybe the colour will be 'faded' also - but does using only 1 drop not effect the pH reading??)

I'd really like to pursue incremently lowering the pH value of test sample with some form of acid and see difference in test colours. Quick maths (with very dodgy parameters) tells me I'd need to use at least a 10litre sample with 1 drop of acid to reduce by around .2 ??) Might try this just for a giggle .....

 

[Brad_C]

I put 0.25L in 19,000L to drop the pH about 4 points. That's about .013ml in 1L. 1 drop is ~1/20ml so you need about 1/4 of a drop. That'd be ~1 drop in 4L for 4 points or ~1 drop in 8L for 2 points. So given it's all approximate your maths seems pretty good.

If you put 5ml of acid in 1L of water you'd then want about 1.3ml of that in your 1L of pool water to bump it up 2 points.
They are more manageable figures if you have a 1L bottle and a graduated pipette.

 

[amlez]

I put 0.25L in 19,000L to drop the pH about 4 points. That's about .013ml in 1L. 1 drop is ~1/20ml so you need about 1/4 of a drop. That'd be ~1 drop in 4L for 4 points or ~1 drop in 8L for 2 points. So given it's all approximate your maths seems pretty good.

If you put 5ml of acid in 1L of water you'd then want about 1.3ml of that in your 1L of pool water to bump it up 2 points.
They are more manageable figures if you have a 1L bottle and a graduated pipette.

Cheers Brad - I'll give that a crack.

Nice pool weather over your way ATM - hope it holds, I'm down in Perth in a few weeks and hope to get some quality Scarborough Beach days in ...... !!

 

[Brad_C]

3pm and it has just dipped below 40. Was forecast 35 today but got to 44 here. Just about to jump in the pool.

 

[ajw22]

3pm and it has just dipped below 40. Was forecast 35 today but got to 44 here. Just about to jump in the pool.

Some of us have to realize you are discussing temperatures in C not F.

 

[Brad_C]

Some of us have to realize you are discussing temperatures in C not F.

Yes, I forget that sometimes. A few years ago I spent a couple of weeks of winter in Minnesota. I like ours better.

In the middle of winter the pool gets down around 12C (54F), but it warms up again pretty quickly. Right now it's about 29C (84F), so on a 44C (111F) day it's just a nice temperature.

 

[lukeyluke]

Hi Amlez

Fellow Aussie here mate also with the CCL kit, which is fantastic. I bought an Apera PH20 pH meter off Amazon as a confirmation tool and have found it very useful. It also helps you to practice interpreting the colour scale.

I know I'm not Robinson Crusoe, but I don't have a great deal of confidence in my interpretation of my pH test results ( I use the Aussie CCL test kit which I believe is similar to the Taylors one used widely in the States?).
The colour scale ranges from yellowy/orange hue at the low end (6.8) , to pinky/red at the 'high' end (7.8).

Now, as much as I'd like to call 7.6, I'm thinking my pH sits in the 8+ range in reality.

Problem is, while I know it's more than 7.2, from 7.4 up on the colour scale, they all appear pink/purple?? to me, but none of them actually match the colour of my sample, which seems a much 'deeper' colour (I wish the colour scale went to 8/8.2 !!). When I say 'deeper' colour, it's a richer colour, but not necessarily pinker or redder?? (Hope I'm explaining myself properly here??).
I test the standard, and I see the 7.2 as it clearly has an orange tinge to it.

What I'd like to be able to do is test the water, get the same reading I always get (7.6 - 8.2 ??? somewhere), then incrementally add a small amount of acid & retest to see the gradual effect on the viewing tube scale - I'm sure this will help me understand which range my normal test sits in.

Does this sound feasible?? - and if so,
1/. How much acid ( I use Hydrochloric Acid) would I need to add to a 500ml (17floz?) sample to reduce pH by .1 or .2 ?? (I envisage using a pipette).
2/. As I don't particularly want to be playing around with dripping Hydrochloric Acid, would I get the same result using vinegar, lemon juice, or some other form of less 'nasty' acid??

Just by the by, I'm adding 500ml of HCL Acid weekly, and the pH reading doesn't ever seem to change (TA also sits fairly steadily in the 75-100 range)

 

[wogster]

I know I'm not Robinson Crusoe, but I don't have a great deal of confidence in my interpretation of my pH test results ( I use the Aussie CCL test kit which I believe is similar to the Taylors one used widely in the States?).
The colour scale ranges from yellowy/orange hue at the low end (6.8) , to pinky/red at the 'high' end (7.8).

Now, as much as I'd like to call 7.6, I'm thinking my pH sits in the 8+ range in reality.

Problem is, while I know it's more than 7.2, from 7.4 up on the colour scale, they all appear pink/purple?? to me, but none of them actually match the colour of my sample, which seems a much 'deeper' colour (I wish the colour scale went to 8/8.2 !!). When I say 'deeper' colour, it's a richer colour, but not necessarily pinker or redder?? (Hope I'm explaining myself properly here??).
I test the standard, and I see the 7.2 as it clearly has an orange tinge to it.

What I'd like to be able to do is test the water, get the same reading I always get (7.6 - 8.2 ??? somewhere), then incrementally add a small amount of acid & retest to see the gradual effect on the viewing tube scale - I'm sure this will help me understand which range my normal test sits in.

Does this sound feasible?? - and if so,
1/. How much acid ( I use Hydrochloric Acid) would I need to add to a 500ml (17floz?) sample to reduce pH by .1 or .2 ?? (I envisage using a pipette).
2/. As I don't particularly want to be playing around with dripping Hydrochloric Acid, would I get the same result using vinegar, lemon juice, or some other form of less 'nasty' acid??

Just by the by, I'm adding 500ml of HCL Acid weekly, and the pH reading doesn't ever seem to change (TA also sits fairly steadily in the 75-100 range)

I think your really looking for the Acid demand test , in the Taylor kits there is an acid demand (CR005 or CR006) , if your measure is 8 or 8+, you can add drops until it matches what you want, and then based on the drop count you need so much acid, based on chart in the manual. You can also use pool math, if your count is 8+, then assume it is 8, aim for 7.4 put in the appropriate amount, wait a couple of hours, with the pump running, and test again, repeat this process until you get 7.2 to 7.8. Also, make sure another test isn't messing things up. If your FC is 10+ then your PH will read 8+ no matter what it actually is.

Realize that the recommended TA, by the pool business, is high, because it causes the pH to go up, and then you need to buy more buffer to keep the TA higher, and then more acid to keep the pH lower, which also lowers the TA. For a non-commercial (personal) pool, you may find a TA closer to 50 works better for you. As for adding acid, it depends on the strength of the acid, this can be expressed as Degrees Baume or as a percentage. Obviously 31.25% (20 Baume ) acid will require a lot less then a weak acid like Vinegar (4%)

 

[AUSpool]

Geday amlez,
What you need is a bottle of the Aussie Gold test solution 3 from a pool shop or Clark Rubber. It’s their acid demand reagent, a very dilute sulfuric acid. If you add it to your treated pH solution (sample + CCL pH indicator) drop wise you will slowly bring down the pH of the solution and go through the range of colours. If you add a grain or two of sodium hydroxide (NaOH, drain cleaner) you will bring you treated pH solution to the top of the range before adding the acid demand solution and ensure you go through the entire range of colours.

The CCL comparator is not exactly the same as the Taylor. I have the Taylor, CCL and BlueDevil and prefer the BlueDevil. The BlueDevil and Aussie Gold comparator colours are in a see through window that more closely matches the sample. If you go out and get the Aussie Gold solution for a bit more I would get there 4in1 kit that includes the pH comparator that is identical to my BlueDevil. It also comes with TA, CH and the acid demand reagent. I would use the CCL pH indicator solution (4-5drops) in the Aussie Gold pH comparator and use the CCL TA and CH tests.

pH comparators, BlueDevil on the left with the OTO chlorine cut off and the Taylor on the right with the CYA cut off. I use the Blue devil pH and the Taylor CYA comparators.