It is a cheleting agent given intravenous for blocked arteries. I got mine from Trailhead Supply in Utah. First heard about it on the MV list. If I can find the original article I'll post a link, it was from a magazine on wind generators and solar systems.
The instructions I had called for draining the old electrolite and inverting the battery( I used saw horses) and flushing the sediment out of the cells until the water is completely clear. For the 6TLs I dissolved a tablespoon of EDTA in hot distilled water and poured it in each cell, then finished filling the cell with hot distilled water to the top of the plates. The first Battery I did( the one in the M51A2) I let sit for a week. Then drained and flushed again and refilled with new electrolite(obtained from a farm supply store. It recovered and I'm still using it four years later with no problems.
The second one was the one in the forklift that had been sitting for several years. I did basically the same thing except I let it sit for about 30 days. After I refilled it with new electrolite I disolved about a teaspoon of EDTA in 30 MLs of distilled water and added it to each cell. Woltage came back at 9 volts on one and 4.5 volts on the other. I completely discharged them and recharged a couple of times hoping to get them to recover, but no luck. Wound up buying new ones.
If I remember correctly I bought the original bottle of EDTA(1 LB) from Trailhead Supply about 5 years ago for $16. Enough to do my two batteries and probably enough to do one more I think.
I takes around a gallon of Electrolite to fill 2 6TLs (around $10 at a farm supply).
Appart from the danger of working with sulpheric acid and labor I figured it was worth a try against the cost of new batteries. I was told by my battery supplier there was no way it would work, but then they have a vested interest in saying that.
That's my sad tale, try it or not it's up to you.