An automatic chemical analyzer utilizes reagents supplied in reagent bottles. The reagent bottles are labeled on their bottom surfaces with an identification label bearing a machine-readable identification code. The automatic chemical analyzer includes a reagent tray having a plurality of tray apertures therein which receive coded reagent bottles and which expose the bottom surface of each bottle for optical viewing of the machine-readable identification code. The analyzer further includes optical scanner means positioned below the reagent tray for reading the machine-readable identification code on the bottom surfaces of reagent bottles within the tray apertures. The tray apertures are selectively located over the optical scanner means so that the analyzer can identify the reagent bottle and the contents thereof.
The identification label has a spaced pair of position reference dots defining and orienting a label area. A plurality of bit fields surround the position reference dots, their positions being defined by the position reference dots. Each bit field maps to a single bit of a multi-bit binary bottle identification code. Bit dots are printed in selected bit fields to define the binary value of each bit of the multi-bit binary identification code.