ran at about 125C for 6 hours and virtually nothing reacted.
You need to be at least 120C inside the flask, IMHO.
I ran phos acid for my first try and failed to react the excess iodine at the bottom of the flask
If the I2 sat on the bottom from the start and would not convert to HI, your phosphorous acid may have already oxidized to phosphoric acid. Or you may have a faulty thermometer. Around 87C, the phosphorous acid and I2 WILL react. It will react energetically at that temp. If you reached that temp and still had a dark iodine layer in the flask, your phos acid is not good. If your phos acid is good, you didn't reach that temperature in the flask.
The flask temperature will be lower than the temperature of the oil bath-- depending on the size of the flask, the depth of immersion, the size of the condenser and the temperature of the coolant for the condenser. You likely did not get the contents of the flask hot enough. If you are certain that you did, your phos acid is suspect.
Meths: Can anyone comment on the use of phos acid extracted from foliar solutions in cooks
Read these threads
Post 456171 (https://www.thevespiary.org/talk/index.php?topic=8316.msg45617100#msg45617100)
(halfkast: "Extracting H3PO3 from phosphite foliar solutions", Stimulants)
Post 476161 (missing)
(suss: "KCl a serious problem in HI/E reactions?", Stimulants)
In summary, you need to minimise unnecessary heat during the foliar extraction procedure. It is assumed that the clear/white waxy solid is a 50/50 mix of H3PO3/H3PO4. For this reason, simply double the ammount required for the reaction and it reacts like a treat.
PM if u need more info 8)
Whats the difference between phos acid and hypo? Is one preffered over the other? for what reasons? etc etc
Hypo, Phos Acid and RP ALL react with I2 to produce HI. The difference is in the rate at which they produce and REGENERATE the HI (to complete the reduction).
Generally, hypo cooks are fastest, taking <3hrs. Phos acid are longer at <12hrs. Lastly, rP LWR's take about 24hrs or more. All produce great product; the choice is solely dependant on which of the three is easiest for you to obtain. Post reaction workup is the same except for the filtering of the RP...
Scottydog:
>>In the phos acid synth the check point is right around 3.5 to 4.5 hrs
>>After 6 hrs, at an oilbath temp of 127C or 142C (doesn't matter) the rxn solution will just recondense down the sides of the flask, with no further conversion of iodine to HI and no further recycling whatsoever
Swix has also noted that 'dead point'; but later on at the 6hr mark. He assumes it is because reaction rate is proportionate to temperature and the concentration of reactants. No two Bees will get these factors the same; so the important thing is to recognise the 'dead point' and proceed from there. Mind you, it wont hurt the reaction to let it reflux for those extra hours ('cept for the electricity bill :-[ ).
add KI or NaI at the outset
Ratios?
Would replacing some or all of RXN H20 with 7% tincture of Iodine work?