An improved device and method for liquid storage and analysis. The device comprises a receptacle defining a U-shaped compartment for a first open-ended branch and a second closed branch. A reaction zone in which the liquid will react with a reagent during analysis is located at the bight interconnecting the branches. The opening in the first branch constitutes a liquid inlet. A wall portion of the second branch spaced from the reaction zone is of self-sealing material which is punctured to release gas from the compartment and to aspirate liquid into the first branch. The material subsequently forms a fluid-tight seal. A wall portion of the body adjacent the reaction zone is made of light-permeable material so that the reaction or the result of the reaction can be optically analyzed. A plurality of such compartments can be provided with a chamber interconnecting the extreme ends of the second branches. A common wall portion of self-sealing material can then be provided for some or all of the compartments.

A method for photometrically measuring a reaction process at a darkened measuring station which contains a sample having an unknown quantity of a substance which acts as a reaction partner with a reagent. The sample is provided with a first reagent which acts as a reaction partner with a reaction partner present in the sample. A first photometric measurement of the sample is taken at the darkened measuring station to measure the reaction process between the first reagent and the reaction partner in the sample, and this first measurement is used for computation. At least one additional reagent which differs from the first reagent and which constitutes a further reaction partner is added to the sample at the darkened measuring station after the first photometric measurement. A photometric measurement of the sample is conducted after the addition of each additional reagent and during the course of a reaction between reaction partners then present. The unknown quantity of the substance in the sample is determined from all the measured values. The first reagent can be added to the sample prior to transferring the sample to the darkened measuring station or can be added to the sample at the darkened measuring station.

A probe for remote spectrometric measurements of fluid samples having a hollow probe body with a sliding reflective plug therein and a lens at one end, ports for admitting and expelling the fluid sample and a means for moving the reflector so that reference measurement can be made with the reflector in a first position near the lens and a sample measurement can be made with the reflector away from the lens and the fluid sample between the reflector and the lens. Comparison of the two measurements will yield the composition of the fluid sample. The probe is preferably used for remote measurements and light is carried to and from the probe via fiber optic cables.