I have to confess that chemistry is my weak point, so I need the help of the chemically inclined. I hope the following isn't too confusing, but MY HEAD HURTS!!!
My Brewcraft Acid Test Kit has almost run out of Sodium Hydroxide (NaOH) 0.2N solution and the kit isn't available here any more. There is plenty of phenolphathlein indicator left (and I guess that indicator from the pool shop is the same if I need more). My plan is to make up some more NaOH solution using high grade NaOH beads from a reputable source since I can't find small quantities of NaOH solution (i.e. 2g NaOH in 250ml of distilled water, 4g in 500 ml, etc) . So far so good!
However, Jolicoeur suggests a simplified TA test using smaller test quantities to get more tests from the kit (see his book P182... using 2.68ml of juice, 3 drops of indicator and the number of mls of 0.2M NaOH x5 = g/L of malic acid).
Andrew Lea has a method using 0.1M NaOH with 6.7ml of juice and number of mls of NaOH to get g/L of malic acid.
I can't quite get my head around the difference between the 0.1M and 0.2M concentrations, and if it is important (probably is!). The Brewmaster Test Kit uses 15ml of sample (adjusted to 13.4 ml to convert from Tartaric Acid to Malic Acid equivalent as suggested by Jolicoeur), and this is 2 x the quantity sample suggested by Lea using 0.1M NaOH. I can see that there must be some consistency between the several methods given that 5x and 0.2 probably normalise them, but I can't figure it out.
So, can anyone who knows about this stuff tell me what is the best way to go, or if the methods all produce the same result. I am not too fussed about TA except it is good to know where it is in the range 5g/L - 7g/L. Unfortunately (for me) I have simply been doing the TA test on a "monkey see, monkey do" or "taste" basis and probably should understand it a bit better.
Thanks for any help.
My Brewcraft Acid Test Kit has almost run out of Sodium Hydroxide (NaOH) 0.2N solution and the kit isn't available here any more. There is plenty of phenolphathlein indicator left (and I guess that indicator from the pool shop is the same if I need more). My plan is to make up some more NaOH solution using high grade NaOH beads from a reputable source since I can't find small quantities of NaOH solution (i.e. 2g NaOH in 250ml of distilled water, 4g in 500 ml, etc) . So far so good!
However, Jolicoeur suggests a simplified TA test using smaller test quantities to get more tests from the kit (see his book P182... using 2.68ml of juice, 3 drops of indicator and the number of mls of 0.2M NaOH x5 = g/L of malic acid).
Andrew Lea has a method using 0.1M NaOH with 6.7ml of juice and number of mls of NaOH to get g/L of malic acid.
I can't quite get my head around the difference between the 0.1M and 0.2M concentrations, and if it is important (probably is!). The Brewmaster Test Kit uses 15ml of sample (adjusted to 13.4 ml to convert from Tartaric Acid to Malic Acid equivalent as suggested by Jolicoeur), and this is 2 x the quantity sample suggested by Lea using 0.1M NaOH. I can see that there must be some consistency between the several methods given that 5x and 0.2 probably normalise them, but I can't figure it out.
So, can anyone who knows about this stuff tell me what is the best way to go, or if the methods all produce the same result. I am not too fussed about TA except it is good to know where it is in the range 5g/L - 7g/L. Unfortunately (for me) I have simply been doing the TA test on a "monkey see, monkey do" or "taste" basis and probably should understand it a bit better.
Thanks for any help.