After you cross a pool of toxic sludge, you reach Test Chamber 09.

Move the Cube

The particle field is between you and the red button, so you can't take the cube through it. You also can't shoot through it to make a portal in the blue room. To get past this, create a portal in this first part of the chamber that you can put the cube through, making it end up on the platform near the orange portal. Then, walk through the particle field, create a blue portal, and pick up the cube from the platform. Go into the elevator to reach Test Chamber 10.