1 ml = 1cc both are a measure of volume
1 mg = 1000 mcg both are a measure of weight
Every given compound is different with its weight/volume ratio. For example, 1 ml of pure gold will weight more than 1 ml of water - the same is true for AAS.
For example, 1 ml of EQ is 1.18 grams
By attempting to convert mcg to ml you are converting apples to oranges - it doesn't work that way.
As a general rule (this is a very rough estimate) 1ml = 1g, but if you are planning on playing with substances that are toxic or harmful you cannot use this general rule (for example clen MUST be dosed out in mcg's, if you make a mistake and hit 1g of it you will be in the hospital)
If you are trying to make a conversion with 40mcg per 1ml do this (I will use clen as an example):
1) Get a vial:
2) fill it with 10ml of the liquid you want to use as a base (BA or whatever).
3) mark where the 10ml level is
4) pour out the liquid
5) pour in 10 dosages of the clen (400mcg)
6) pour in the fluid until it is at the 10ml level you marked
The solution is now 40mcg per ml.
Also realize the solid will displace the liquid. If you go straight with 10ml of liquid and then throw in the powder it will be less than 40mcg per ml.