Chemical analysis method using reaction container

For use in measuring the extent or rate of optical density change produced by a reaction a rigid or semi-rigid disposable reaction container is disclosed of the type comprising a windowed reaction chamber adapted for the transmission of light therethrough and an auxiliary chamber that is separated from the reaction chamber except for an opening which is small enough to prevent substantial diffusion or movement of liquid from one chamber to the other when under static conditions but through which a solution of a reagent in the auxiliary chamber may be forced so as to enter the reaction chamber and commingle with a solution of another reagent and thereby trigger a reaction, improvements comprising the provision in a receptacle having side walls, end walls and a bottom wall of a projection which extends a substantial distance upwardly from the bottom wall so as to separate the lower part of the receptacle into two portions adapted to separate liquid in one of said portions from the other portion in combination with a cover having a downwardly depending divider which terminates in closely adjacent spaced relation to said projection, said projection and said divider separating said receptacle into a reaction chamber and an auxiliary chamber separated from each other except for the opening or passage that is provided by said closely spaced relation between said projection and the lower end of said divider. The parts preferably are dimensioned and arranged so that said opening is in the form of a passage of substantial length and is positioned so that nearly all of a solution in the auxiliary chamber may be forced therethrough into the reaction chamber. The receptacle preferably is in the form of one molded piece and, as said, the cover is sealed in place with a lyophilized reagent in at least one of the chambers. Preferably the aforesaid passage is of such restricted cross-section as to prevent gravitational flow of aqueous liquid from one of said chambers to the other when the level of liquid in said chamber is substantially above the uppermost portion of said passage and is substantially above the level of any liquid in the other chamber while being large enough to permit, responsive to applied pressure, the forcing of aqueous liquid through said passage so as to be injected into the other chamber and thereby become commingled with liquid in the other chamber.