Abstract: A method of obtaining small representative solid-phase samples from a large solid-phase sample. Solid-phase material is optionally separated from any liquid-phase that may be present and is mixed. A portion of the mixed solid-phase particulate sample is selected which provides an intermediate size representative sample. After adding liquid diluent to the intermediate particulate sample in a vessel, the suspension is agitated to promote separation of small particles as may be adhering to large particles to obtain a homogeneous suspension. Agitating is preferably carried out using a magnetic stirring bar. Fractions of this homogeneous suspension are then obtained by aspirating using a pipette and transferred to test tubes which will constitute small, truly representative solid-phase particulate samples from which replicate testing can be confidently performed.

Abstract: A method for compensating toxicity test data for the measured toxicity of a reference sample by the steps of:a. obtaining toxic response data for a plurality of concentrations of at least two different test samples, including reagent controls having zero sample concentration for each sample;b. defining the sample having the smallest toxic response at high concentrations as the reference sample;c. computing the toxic response of the test sample relative to that for the reference sample for at least two concentrations in accordance with the equation:relative gamma=.GAMMA..sub.R =(L.sub.SC /L.sub.SX)(L.sub.RX /L.sub.RC)-1, where L.sub.SC =light output of the test sample control (i.e. for X=0),L.sub.SX =light output of the test sample for concentration X,L.sub.RX =light output of the reference sample for concentration X,L.sub.RC =light output of the reference sample control (i.e. for X=0); andd. generating a dose-response curve of concentration versus relative .GAMMA.

Abstract: A temperature control apparatus for controlling the temperature of a plurality of cuvettes consisting of an annular sealed chamber containing a refrigerant, means fixed to the sealed chamber for receiving the sample cuvettes, a heater in thermal contact with the sealed chamber, and a temperature sensor in thermal contact with the sealed chamber. The sealed chamber may include a plurality of thermally conductive posts fixed to the chamber, the spacing between adjacent ones of the posts being adapted to receive the sample cuvettes.

Abstract: An apparatus and method for indicating the temperature of the environment into which a reaction vessel may be placed is provided by a container holding a thermally efficient fluid. The container has an identical external configuration substantially identical to the reaction vessel and is adapted to be positioned within the environment in place of the reaction vessel. A temperature sensor in thermal communication with the thermally efficient fluid provides an electrical parameter indicating the temperature of such fluid and thus the environment of the reaction vessel.

Abstract: A sample holder and shutter assembly for photometers is disclosed in which a stationary sample chamber body is mounted in close proximity to a photosensitive device. A light path is provided from the sample chamber to the photosensitive device and shutter means is provided for selectively interrupting and opening the light path between the photosensitive device and the sample chamber without moving the sample chamber. Heat exchange means including a heat pump and a heat reservoir are provided for maintaining a desired temperature in the sample chamber. The sample chamber body is thermally connected to said heat pump and is preferably thermally isolated from the means mounting it. In one embodiment, the heat pump and heat reservoir are flexibly connected.

Abstract: A heat exchanger comprising:(a) a housing having an interior surface;(b) a thermally conductive member in intimate contact with the housing;(c) a thermally conductive element coaxially disposed in said housing and having an inner and an outer surface and in thermal communication with the member, wherein the inner surface of the element defines a first fluid passage, and wherein the interior surface of the housing and the outer surface of the element are in spaced relationship thereby defining a second fluid passage, the first and second fluid passages being in fluid communication;(d) a first port for maintaining the first fluid passage in fluid communication with a first external fluid;(e) a second port for maintaining the second fluid passage in fluid communication with a second external fluid; and(f) means for regulating the member's temperature; wherein heat is transferred between the member and the element via solid conduction.