420 is opened and the pump 424 pumps and or urges a portion of the second sample from the second chamber 428 through the third flowline 406 and toward the sensor 432 the sensor 432 may be an optical density sensor that determines a second value of a parameter and or optical density value for the second sample with the optical densities of the first and second samples obtained the first valve 417 in the closed position and the fourth valve 430 directing fluid flow toward a mixer 435 the respective pistons 422 and 424 pump and or urge a portion of the first and second samples from the chambers 426 428 through the flowlines 404 406 and or 402 and toward the mixer 435 the pistons 422 and 424 may selectively and simultaneously pump the first and second samples at the same similar or different flowrates the mixer 435 may be an active and or passive mixer including a torturous flowpath that accelerates the rate at which the samples mix mixing the samples may cause asphaltenes to flocculate from the mixture in this example a filter 436 is positioned within the flowpath of the mixer 435 the filter 436 is configured to substantially prevent flocculated asphaltenes from flowing therethrough after the mixed fluids have passed through the filter 436 the mixed fluid samples are directed through and or adjacent to a second sensor 438 through a check valve 440 and back to the bypass flowline 408 the second sensor 438 may be an optical density sensor that determines a third value of a parameter and or optical density value of the mixed samples to determine if and or an amount of asphaltenes that may have flocculated when mixing the fluid samples.