I bought MSM thru Kirkmans (I should own stock in the place!) They suggest 1/4 teaspoon 2 times per day for an adult. So, I give him 1/4 teaspoon devived by two so he gets 1/8 teaspoon.
I put it in soda (sprite) and he has no trouble drinking it. It does seems to stabilize the mood from the sulfer drops after chelation is over. I don't give it to him while he is chelating.