Abstract: A powder composition which is readily dispersible in a liquid such as water without clumping, comprises a powder the particles of which are uniformly coated with an effective amount of a surfactant, preferably Polysorbate-80, sufficient to enable the powder composition to readily disperse in the liquid. A process for making the powder composition that disperses readily in a liquid without clumping, comprises the step of continuously mixing a powder with an amount of a surfactant for a time sufficient to uniformly coat at least substantially all of the particles of the powder with the surfactant.

Abstract: A circular bar code includes first teeth directed radially inward from an outer ring and defining a radial position at which information is encoded and second teeth, tooth directed radially outward from an inner ring and opposing a corresponding one of the first teeth, wherein the information is encoded based on subdivisions of a gap between opposing first and second teeth. In one implementation, the circular bar code is printed on a disk coated with an antibiotic. The disk is used for determining the effectiveness of the antibiotic in killing bacteria, wherein the circular bar code provides identity and concentration information for the antibiotic.