you can measure the density of plastic using an instrument called electronic densimeter. this densimeter give you the density measurements very easily and fast. below is few models of this instrument.
http://www.worldtesters.com/Tester_Meters/Densimeters.htm
specific gravity test
An aerometer is an instrument used to measure the mass and density of gases.
ocotypergram
a viscometer is used to determine viscosity(density) of a liquid.
Post-menopause unless there's a reason to do it sooner.
this is an instrument in the laboratory that is used to clean various kinds of test tubes.
Plectrum
Piano
opacimeter
Spirometer
That sounds like density centrifugation...So, a centrifuge?
A bone density test employs x-rays to measure the amount of calcium and other bone minerals are retained with the bone segment. A bone density test is used to diagnose osteoporosis.