Help with Palintest chloride test

[smeestu]

Hi all im trying to confirm the Salt level in my pool getting a red light on the swg unit a emaux 45g/ph which this error light means not enogh salt /check cell .The unit is not very old been having this problem on and off since i bought it and have blindly added salt untill the light went out .We did have some really heavy rain 2 days ago and the pool over flow was runing over night .I bought a palintest Chloride tester to take the guess work out of it but unfortunatlly the instructions that came with it said use a 2ml sample top up with distilled water to 50ml then add tablets untill it goes from yellow to brown which is pretty straight forward but it tests in 500ppm increments . The spare tablets i bought came with paper saying you can test 100ppm using a striaght 10ml sample but obviously im not going to be able to disolve 40+ tablets in 10 ml sample so i need to up the scale a bit can any point me in the right direction . Living in Thailand i am very limited with what i can use .Thought the swg would be a major bonus running the pool but its been a pain in the arse so far . im concerned it might be running too low as it doesnt seem to be generating the chlorine it is supposed to

 

[Patrick_B]

Hey smeestu,

Sorry you're having salt cell problems, and it's always tougher advising you being where you are with the limited options. Please understand I'm just double checking by asking this, but are you sure those multipliers are correct for the reduced sample sizes? If so, I would try duplicating the larger sample size test again a couple of times to get as close as you can. Salt cells can be a bit of a pain with erroneous readouts on salt levels as you are painfully aware. Just to cover another base, are you sure it isn't due to heavy load on the pool? I ask because I remember times where many, many people are swimming in there sometimes. Lastly, is there any chance you can order, or find another chloride test or salt only test strips? Sorry,must trying to think of all possible options to help you.

 

[chem geek]

I presume you have the Palintest SP 622 salt test. With their instructions, you would use around 6 tablets for getting to 3000 ppm. The test is a titration test that adds silver to produce silver chloride until the chloride gets used up at which point the silver reacts with the potassium chromate dye to form the red/brown colored silver chromate product. The test is done between a pH of 7 and 10 because below a pH of 7 chromic acid is formed so there is less silver chromate formed while above a pH of 10 brown silver hydroxide forms so interferes with the visual endpoint of the test.

Whether or not you dilute the initial 10 ml water sample to 50 ml will not change the number of tablets you would use -- you would end up with exactly the same result. This is true for most of the titration tests -- diluting the sample with distilled water does not change the result.

In order to get to 100 ppm resolution per tablet, you need to use a larger undiluted water sample. That means a straight 50 ml sample of water (not 10 ml). You will now have 5 times the amount of chloride and will use 5 times as many tablets so 3000 ppm would use around 30 tablets, but each tablet would represent 100 ppm salt. You should have no problem dissolving the larger number of tablets in the larger sample size since it's proportionally the same as your 6 tablets in 10 ml.

 

[smeestu]

I presume you have the Palintest SP 622 salt test. With their instructions, you would use around 6 tablets for getting to 3000 ppm. The test is a titration test that adds silver to produce silver chloride until the chloride gets used up at which point the silver reacts with the potassium chromate dye to form the red/brown colored silver chromate product. The test is done between a pH of 7 and 10 because below a pH of 7 chromic acid is formed so there is less silver chromate formed while above a pH of 10 brown silver hydroxide forms so interferes with the visual endpoint of the test.

Whether or not you dilute the initial 10 ml water sample to 50 ml will not change the number of tablets you would use -- you would end up with exactly the same result. This is true for most of the titration tests -- diluting the sample with distilled water does not change the result.

In order to get to 100 ppm resolution per tablet, you need to use a larger undiluted water sample. That means a straight 50 ml sample of water (not 10 ml). You will now have 5 times the amount of chloride and will use 5 times as many tablets so 3000 ppm would use around 30 tablets, but each tablet would represent 100 ppm salt. You should have no problem dissolving the larger number of tablets in the larger sample size since it's proportionally the same as your 6 tablets in 10 ml.

Thanks for both replies i will go and test now with your recomendations I made a mistake in the first post as in the test kit said 2ml diluted to 50ml give you a 500ppm resulution sorry for the confusion i caused The ph is fine rock steady at 7.6 since i put the swg in for some reason the ph stays between 7.6-7.7 for months at a time as soon as it goes to 7.8 i drop it down again . The test is as you say the sample starts off at a yellow colour and clearly changes to a brownish colour.Here is a copy of the instructions that came with the extra tablets if photos arent allowed here is a dropbox link Dropbox - 2015-07-21 11.04.59.jpg. Once again thanks for all the help here ive learnt so much over the last year or so from this site

- - - Updated - - -

Just as a foot note the orginal test kit doesnt say anything about multipling the result by 1.64 when diluting the 2ml sample with 48ml of distilled water .This is only written on the extra tablet paperwork

 

[chem geek]

The salt level that people usually refer to for saltwater chlorine generators is in ppm sodium chloride units so yes you would multiply the result by 1.64.

 

[smeestu]

The salt level that people usually refer to for saltwater chlorine generators is in ppm sodium chloride units so yes you would multiply the result by 1.64.

Thanks for the reply again so just to be "idiot proof" if i take the 10ml sample as on the instructions that come with the tablets shown above and dilute to 50ml so i can disolve maybe 40 tablets ( my swg recomends 4000-4200ppm) i will get the required result in 100pmm when multple by 1.64

 

[chem geek]

They say to subtract 1 from the number of tablets you add. This is because of a small bias in the test. So for 4000 ppm it will take around 4000/100/1.64 + 1 = 25 or 26 tablets. So if a 10 ml sample (diluted to whatever reasonable amount you want, so 50 ml is fine) were to take 27 tablets, then this is (27-1)*100*1.64 = 4264 ppm salt.

 

[smeestu]

They say to subtract 1 from the number of tablets you add. This is because of a small bias in the test. So for 4000 ppm it will take around 4000/100/1.64 + 1 = 25 or 26 tablets. So if a 10 ml sample (diluted to whatever reasonable amount you want, so 50 ml is fine) were to take 27 tablets, then this is (27-1)*100*1.64 = 4264 ppm salt.

Thanks again just done the test as above and at 23 tablets changed colour 24 a bit darker 25 no change so i know now for sure that the salt is too low dont know at what point the low salt light comes on but i will take it up to 4200 now maybe it will help the swg make more chlorine . Anyways with your help i have a starting place
if i go with 24 -1 =23x100x1.64= 3772 i have been using salt from some local salt flats about 15km away so off to get some more bags looking at pool math 1 more 40kg bag should do it then ill chck it once a month hopefully that should be ok though we are just into the monsoon season here now

 

[Patrick_B]

Good deal!

Will this be your first monsoon time with the pool smeestu? I'm guessing with monsoons, your pool will change a little Chemistry wise. :joker:

 

[smeestu]

Good deal!

Will this be your first monsoon time with the pool smeestu? I'm guessing with monsoons, your pool will change a little Chemistry wise. :joker:

I was here last year and the pool turned into a swamp i had no idea what i was doing and listening to the wrong information from the "experts" which was trichlor alum vacum thriclor alum vacum .This year i think ill get some more trichlor powder in a atempt to keep the CYA up a bit as everything gets diluted down as i dont think the swg will keep up unless i run it for really long periods of time which will cost too much but i do feel a bit more confident this year as i think i have a basic understanding now thanks to TFP