Abstract: This invention relates to a method for preparing radium-free standard solutions of radon-222-in-water of known concentration for use in the more accurate calibrating of liquid scintillation counters than obtainable by the use of radium-226 as standards for calibration. A radium-free radon-in-water standard of the type contemplated herein is defined as a known volume of deionized water with a known activity of radon gas without the presence of any radium activity. This new method provides for the rapid, accurate and inexpensive analysis of Radon-222 water samples by utilizing standards whose activity is derived from actual instrumental quantitative analysis as opposed to problematical mathematical derivation.

Abstract: A magnetic compass is illuminated by a light emitting diode. The compass is nclosed in a case made of a lightweight, plastic composite material. The light-emitting diode is energized by a low profile, nonmagnetic battery connected to the light emitting diode through a nonmagnetic microswitch operated on the exterior of the casing by a pushbutton. The compass has a compass rose with strips of phosphorescent material disposed thereon, a rotatable bezel with a strip of phosphorescent material thereon and a lid having a sighting slot therein traversed by a cross hair. Located at the bottom and top of the cross hair are additional strips of phosphorescent material so that the compass may be utilized in the dark. The phosphorescent material may be charged by ambient light and by light emitted by the light emitting diode.