Abstract: A multi-color image forming apparatus is capable of decreasing the amount of ozone generation which occurs during the formation of a multi-color image. For this purpose, a charged latent image having a tri-level electric potential is formed on a positive charging photoconductor by a charging means and an exposing means. A first color toner having one of a positive polarity and a negative polarity is caused to adhere onto one of the charged latent images having the highest electric potential level at a first developing unit of the apparatus, and a second color toner having the other polarity is caused to adhere onto the other of charged latent images having the lowest electric potential at a second developing unit of the apparatus.

Abstract: An analyzer has a reaction disk for holding a plurality of reaction containers and a fluorophotometer for measuring fluorescence stemming from solutions in the containers. Most of the containers contain solid phases attached with antibodies but at least one container does not contain any solid phase. In normal operation of the analyzer, a test sample containing antigens and a latently fluorescent reagent such as an antibody labeled by an enzyme are added to a container containing a solid phase. In this container, a fluorescent substance is created through an enzyme reaction. Light is irradiated on the container and the fluorescence emitted from the fluorescent substance is measured. While measuring test samples, fluorescence stemming from a reference sample, such as quinine sulfate, is measured to produce values for the reference sample by which measured values for the test samples are corrected.