To convert 200 mg to mL, you need to know the density of the substance you are measuring. The formula for converting milligrams (mg) to milliliters (mL) is:
mL = mg / density (mg/mL)
For example, if the density of the substance is 1 mg/mL, then 200 mg would be equal to 200 mL. However, if the density is different, the conversion will vary. Always check the density of the specific substance to get an accurate conversion.