Usually the supplied concentration is too great and requires dilution with high purity water to make a working solution. In microscopy for a given application the number of particles used, regardless of size, needs to be fairly uniform. Specific gravity of spheres is 1.05. The solution contains an antibacterial agent. Twelve different particle sizes are available singly or as three sets of four sizes.
Lids are colour coded within each set to help avoid cross contamination.
Sizes are nominal and the actual size is indicated on the vial. This test specimen is made on a holey carbon film which has been shadowed with gold and a coating of graphitised carbon particles. Particles protruding over the edge of a hole are best for testing TEM high resolution performance. The evaporated gold forms small poly-crystalline islands and within these islands lattice fringes can be resolved. This specimen is also used to measure contamination rates in the electron microscope by noting the deposition rate of carbon within the holes of the gold film.