The bulk density of a soil with portion density of 2.65 g/cc and pore space 40% would be

Bulk density is an indicator of soil compaction. It is calculated as the dry weight of soil divided by its volume. It is expressed in grams per cubic centimeter.
Portion density = 2.65 g/cc
Pore space = 40%
Putting on the formula.
$$\eqalign{ & {\text{Pore space }}\% = 100 - \left( {\frac{{{\text{bulk density}}}}{{{\text{portion density}}}}} \right) \times 100 \cr & 40 = 100 - \left( {\frac{{{\text{B}}{\text{.D}}}}{{2.65}}} \right) \times 100 \cr} $$
Solving this,
Bulk density = 1.59 g/cc