Abstract: A light returning target for a photometer. The light returning target comprises a ball lens, and a cradle. The cradle has a hemispherical receptacle in which the lens is intimately received. Preferably, the lens is formed of fused silica, the receptacle is polished sufficiently to reflect, more than it scatters, light, and at least the surface of the receptacle is formed of a material that absorbs, more than it reflects, light.

Abstract: A light returning target for a photometer. The light returning target comprises a ball lens, and a cradle. The cradle has a hemispherical receptacle in which the lens is intimately received. Preferably, the lens is formed of fused silica, the receptacle is polished sufficiently to reflect, more than it scatters, light, and at least the surface of the receptacle is formed of a material that absorbs, more than it reflects, light.

Abstract: An apparatus that conducts in situ analyses of fluids in real time is disclosed. The apparatus comprises bifurcated optic fibers, a pulsed light source, a light detector, a water-tight pressure case that houses the pulsed light source and the light detector, and a flow-through cell that receives one end of each bifurcated optic fiber. The flow-through cell may comprise a plurality of attached tube sections that define a volume which acts as a passageway for conducting fluids. One or more sections of the flow-through cell may be adapted to introduce a reagent into fluid flowing through the cell. Sections of the cell may contain potassium periodate and N,N-diethylaniline that are released into a fluid flowing through the passageway, enabling the spectrophotometer to analyze manganese (II) concentrations by monitoring the decrease in fluorescence accompanying the oxidation of DEA to 2 DEA'. The fluid may also be analyzed by measuring reflectance, absorption, turbidity, and fluorescence.