Abstract: A curtain wall (12) used to divide the shaft in a shaft construction (10) is made of panels (26) in the shapes of parallelograms. Side edges (28 and 30) of the panels (26) are received in channels (18 and 20) in the peripheral wall (16) of the shaft construction. These side edges are parallel to each other, and the perpendicular projections of each side edge are substantially non-overlapping with the other side edge. The result is that the panels can be lowered lengthwise into place and then rotated into the proper orientation. The panels can therefore be lowered through smaller openings than rectangular panels can, and they do not have to be lowered by "chivvying," as rectangular panels do.

Abstract: A chemically integrating dosimeter for measuring gases, composed of a dual membrane system and an internal electrolyte solution. The outer membrane is a gas permeation rate controlling membrane. The inner membrane is a microporous hydrophobic protective membrane interposed between the electrolyte solution and the outer membrane. The dosimeter makes accurate determinations of time integrated exposures to various gases in the atmosphere and can be conveniently used by workers in industrial environments over a wide range of field conditions.

Abstract: An improved flow independent method for electrochemical monitoring of a sample stream for the total concentration of a series of ionic species of the form X.sup.-n, H.sub.m X.sup.-n+m where n varies from 1 to m and X.sup.-n is an anion selected from the group consisting of fluoride ion, F.sup.-, and sulfide ion S.sup.-2. The pH of the sample stream is adjusted to a value below the pk.sub.a of the neutral most protonated species of the series. A first electrode sensitive to the activity of X.sup.-n is placed in the adjusted stream. The electric potential developed thereby is measured. A second electrode sensitive to the activity of hydrogen ion H.sup.+ is also placed in the adjusted stream. The electric potential developed thereby is also measured. The potential difference between the first and second electrode is a measure of the total concentration of the series X.sup.-n, H.sub.m X.sup.-n+m.

Abstract: In a potentiometric system for measuring low levels of ion activity, a method of adjusting the pH in a sample stream by the passive addition of low molecular weight acid or base reagent, without dilution of the sample stream, and without introduction of any interfering, reactive or test ions into the sample stream. A membrane is provided, permeable to the acid or base reagent used to adjust sample stream pH, and impermeable to ionic species. The membrane is placed between a reagent reservoir and the sample stream. Constant flow of the sample stream by the membrane maintains the reagent partial pressure differential between the reservoir and the stream, causing diffusion of reagent through the membrane into said stream.

Abstract: An electrode preferentially sensitive to the activity of zinc ions Zn.sup.+2 in solution. A liquid organic phase containing an appropriate liquid ion exchanger and solvent is combined with means for containing the liquid organic phase as an interface between the organic phase and the solution. Electrical contact with the liquid organic phase at a fixed potential is provided. Zinc ion activity is measured using a standard calomel electrode as a reference, from which the zinc ion concentration is determined.

Abstract: An electrode sensitive to halide ion X.sup.- in solution, the ion-sensitive portion being an imporous membrane of a solid amalgam, such as gold and mercury, in combination with a finely divided salt of mercurous and halide ion X.sup.-, e.g. of the form Hg.sub.2 Cl.sub.2.

Abstract: An improved electrochemical reference electrode for use in potentiometric determinations of species in solution. The body of the electrode is composed of a material substantially permeable to liquid water whose exterior surface, excepting a comparatively small area, is covered by a membrane through which water may pass only by diffusion and which is also ion impermeable. The small area which is not covered forms an opening through the membrane to the body. The body contains a saturated salt slurry. When the electrode is immersed in an aqueous sample solution, water diffuses through the membrane and is transported in bulk across the body. Upon entry into the slurry, the water dissolves the solid salt in the slurry to produce an electrolyte which in turn flows outward through the small area of the body which is not covered by the membrane, whereby a liquid junction is provided between the electrolyte and the sample solution.

Abstract: In a potentiometric system for measuring low levels of ion activity, a method of adjusting the pH in a sample stream by the passive addition of low molecular weight acid or base reagent, without dilution of the sample stream, and without introduction of any interfering, reactive or test ions into the sample stream. A membrane is provided, permeable to the acid or base reagent used to adjust sample stream pH, and impermeable to ionic species. The membrane is placed between a reagent reservoir and the sample stream. Constant flow of the sample stream by the membrane maintains the reagent partial pressure differential between the reservoir and the stream, causing diffusion of reagent through the membrane into said stream.

Abstract: A dual biased magnetic transducer capable of sensing magnetically recorded data on a magnetic medium without any relative velocity between the transducer and the medium. The transducer includes a third DC bias field for aiding the DC field created by the data on the medium for substantially shifting the level in the AC carrier, thereby producing a computer compatible intelligible signal.