Abstract: Methods and apparatus for measuring electrical parameters of a test fluid are disclosed. The methods include maintaining the test fluid and a reference fluid at the same temperature and in thermal proximity to each other, equalizing the temperature of the test fluid and the reference fluid prior to the measuring step, measuring the electrical parameter of the test fluid and the reference fluid at substantially the same time, and standardizing the measurement to a predetermined temperature. The apparatus includes a heat exchanger for maintaining the flow of a primary heat exchange fluid in thermal proximity to the test fluid in the reference fluid, and a metal wall having one surface in contact with a measuring cell and another surface in contact with the flow of the primary heat exchange fluid whereby the measuring cell and the heat exchanger are separated thereby.

Abstract: A surface bolt adapted to be mounted on an inner or outer surface of a closure member, such as a door or window, the bolt being slidable in guides between positions into and out of engagement with a keeper. One of the guides is provided with means to receive the bow of a padlock in two positions, in one position to prevent unlocking of the bolt or, in the other position to prevent locking of the bolt. The bolt may have a recess extending across its outer surface, positioned and dimensioned to be engaged by one of the guides in the locking position of the bolt and to be resiliently and releasably held in such engaged position by a spring.