Hi,
I've tried before extracting DMT successfully using Cybs' Hybrid ATB 'Salt', now I'm planning to try DMT again and want to extract only 100mg DMT because I don't want to waste my bark, so my question is how much vinegar and salt/lye to use ? I read that you can't multiply the ingredients for big quantity of bark but what for small quantity?

That's a kind of refreshing question

Scaling down is probably safer than scaling up in terms of how the arithmetic works out. You will have to be utterly methodical in your working process because any losses will be of greater significance. All equipment needs to be smaller to minimise losses through surface adhesion, and the amount of DMT held up in the naphtha post freeze precipitation will also be more significant if you use anything but the minimum necessary amount.

Adding water to the bark will likely also require your special attention because you are dealing with a situation where there is an interplay between surface area and volume and these do not scale in the same way. I suspect you may have to add a little more water than the mathematically scaled amount in order to achieve a workable consistency.

Why are you extracting such a tiny amount of bark? If you have even 25g available I'd suggest you use that amount - it will give a far more favorable balance between effort and reward.