RSVP International White Marble Mortar and Pestle

Q: Would this be a good choice to grind down things like sulfur and potassium nitrate?

i use mine to grind little pills into powder so i can put them in cmy cat's food and it is just great.it's heavy enough to be sturdy and not slide around. i'm very pleased with mine. good luck

Q: Is the pestle long enough to grip with the hand firmly while grinding and Not scrape the hand on the edge of the bowl?

I had no problem gripping the pestle while grinding. I'm a size small woman. The pestle measures 5 1/2" from tip to end, the depth of inside the bowl is about 2 1/2", the top of inside bowl measure 3 3/4" cross. This should give you some idea if it fits your hand. My problem with the set is that it doesn't grind pepper corn and garlic very well. See my other posting.

Q: I want to use this to mash avocado for my husband who can't swallow chunky things. Will it work for that?

It will work for that, but understand that this item is very small and shallow. At best, you would have to put very small pieces of avacado in this, each at a time, to mash it.