Tony, the only contaminate that would adversely affect the bio using methoxide dried with cement or CaO would be calcuim soap. This will only be present if some cement/CaO fines have found their way into the methoxide added to the oil.

The reduction in glycerol volume is an indication that less soap has been produced. If glycerol is cracked with conc sulphuric the top FFA layer formed is an indication of the original soap content of the glycerol, which is on average in the order of 35% by volume. Do this test with glycerol from dry oil and methoxide ex the imisides drying method and the FFA layer is virtually non existant.