Hi all. Been playing, and decided to see if I could make some peroxalic acid, seeing as it appeared that no-one had tried it (I used TFSE as thoroughly as I could...)
OK, first of all. Tried to tan some hides a while back (miserable, SMELLY failure...), but it meant that I had half a container of lab grade oxalic acid lying around. Couldn't get my hands on any H2O2, but read that Sodium Percarbonate would work as a substitute. So, I took a couple of spoonfulls of oxalic, added a fair heap of 27% Sodium percarbonate washing powder (the rest, I assume, would be sodium carbonate and a little soap powder, judging from all the bubbles!). Add water, the whole thing goes crazy. Gas was evolved (not a huge amount, and stupidly I didn't even do a basic flame test to see what it was! Next time! I would, however, guess that it would be CO2). There were no indicators of what happened, so I added about 1mL of 30% HCl. The solution went almost instantly a light yellow-green colour, and stayed that way. I seem to remember reading somewhere that a peracid has a yellow tinge (or am I deluded?), so I took this as a promising sign (did the acid act as a catalyst - peroxalic acid should form rapidly, faster then performic, but would HCl help?), as I have never made or used a peracid of any type before and thus didnt really know what to look for. Either that, I thought, or it could be chlorine being oxidised by the peroxide. I tested this by mixing up some of the washing powder in water and adding a heap of HCl - the solution went a darker green but cleared up reasonably quickly. Also, CO2 (I assume - flame test) was evolved (from HCl + Na2CO3?) in large enough amounts. I was unable to do further testing, but I think this bears further investigation. Oxalic acid has a pKa about 1 less than Formic (which is in turn 1 less than acetic. And no, I cant remember exact values off the top of my head). This could lead to incresed yield, or at least decreased reaction time, if used as in a buffered performic...