Ml converted to mg or mg converted to ml

Ml converted to mg or mg converted to ml   (06/03/2015, 12:41 PM)

I'm trying to figure out how to measure a powder which is Boron to liquid which I think is the ml I'm doing this in my kitchen and using teaspoon so how many teaspoons of powder does it take to make 100 ml of liquid ? Can you help me? Anna