Cant get PH above 12.5 with sodium hydroxide.

[slipee]

Has anyone else had this problem?? Im using diggers 99% Sodium Hydroxide. mixing at 25 grams per 250 mls, gives a PH of 12.5. Anything stronger drops the PH to 11 or so... My PH gauge is fine and calibrating correctly...Ive also double checked with PH papers.. Can any body help me with this problem, as diggers sodium hydroxide is the only 99% stuff i can find... Cheers

 

[quantumbrujo]

The problem is you PH meter.go see the post Posted: Sun Aug 12, 2007 12:51 am Post subject: -------------------------------------------------------------------------------- To get a PH meter that is super accurate you would have to spend all kinds of money.Maybe your water is just slightly acidic for it not to read 7. did you try it with tap water or bottled spring water or distilled water?don't worry too much about the .3.when you acidify anything between 2 and 3 is good,and when you basify just pour in the base slowly while mixing till the solution gets all black and then add about ten% more to make sure you're up near 13.4.I used to use my PH meter,but the last couple of time I just go by the"let's watch it turn black and add a little more" technique and I'm yielding 1% from my rootbark.Is your PH meter "the Checker" the little red one?One thing that happens with those is that after a few uses they fuck-up and you will be adding your base and the PH will show rising till about 12 - 12 .7,then even if you continue to add NaOH all of a sudden you see it reading lower and no matter how much base you add it stays around 12.then you decide to check the PH of Potassium Hydroxide and you get a 14 reading.go figure _________________ I tried to say no to drugs but they wouldn't listen The difference between theory and practice is much smaller in theory than it is in practice

 

[slipee]

cheers quantumbrujo, my gauge is a hanna PH-EC-TDS meter. Its not cheap, retails around $450. i am sure it works correctly as i use it regularly for, um, other activitys. its also calibrated with PH calibration solution.. I havent used it to read such high PH readings before, I will check it against my mates gauge... For ya, watch it turn black, method do you use around 50g/500ml for your base solution?? Thanks again for your advice..

 

[quantumbrujo]

What I do is,in a seperate HDPE Botltle I prepare a saturated NaOH solution.In other word i just put lye till no more will dissolve.Then I mix it well before.Then very slowly pour some in my rootbark soup.By the way start off with ice cold water cause as the NaOH dissolves it gets extremely HOT. At first the soup gets gray,keep adding very little at a time while constantly stirring not to get PH spikes.Just after it gone grey you will see it all turn Black.When it's all black just add a little more of your NaOH solution just to make sure you are up there near 13.4.If you toutch this black liquid it should feel slippery almost like dish soap.rinse with lots of cold water immediately though..Now getting back to your PH meter.just for fun try reading KOH (PH plus from a hydroponic shop) I bet you will get a 14 reading.