Analytical Method for Determination of Long-Life Carbon C14

Abstract

417nig. of arsenic metal precipltate. soy0 complete for a precipitate heavier than j mg. per sq. and is equal to 22% for a precipitate of about 2 mg. per $9 rm Self-absorption is more than F. Pyrex-quartz graded seal C. Silvered portion of flask H. High-vacuum pressure stopcocks I . Ion trap (very coarse silvered fritted disk and silvered glass tube) J . K. Fiber-repelling post L. Gold-plated quartz fiber M. Electroscope charge button A'. Portion of flask coated with colloidal graphite (Aquadas) 0. Thin coat of ceresin wax P. Brass adapter P '. Brass straps 0.95 inch (4 in all) P". Brass colldr provided with screw for cinching straps Q. Rubber-stoppered hole 0.375 inch, in brass adapter (4 in all) R. Lauritzen electroscope frame R'. Electroscope tube containing objective, scale, and eyepiece S. To vacuum system T. To mercury vapor pump Ion collecting wire (3-mil tungsten)

Analytical Application of Radiochemical Techniques

“…The preparation and purification of tracers to be used in later experimentation often require that no additional nonradioactive isotopes of the radioelement be introduced in the purification and conversion steps. Many procedures for the preparation of high specific activity (radioactivity per unit weight) organic compounds have been published (21,28,40,70,75,78,91,95,96). The preparation of labeled inorganic compounds is simpler, since a greater number of quantitative and often single-step reactions are available.…”

A Comparison of Two Methods for Correcting for Self-Absorption of Beta Particles, Using Sulfur35.

“…where E is the maximum energy of the beta particles. The constant b in equation 1 may have values from 4 to 10 depending upon the shape and energy of the beta spectrum, the type of detector, and the counting geometry (9,10,14,20). For sulfur35, which has a maximum energy of 169 k.e.v.…”

“…For sulfur35, which has a maximum energy of 169 k.e.v. (2), the value of R is 35.3 mg./cm.2 By plotting a curve for a given sample material, the value of b may be calculated by use of equation 1. The true activity A T, that is, the activity that a given sample would exhibit if it were of zero thickness, may be related to the observed activity A0 by the following relation (9,10,14,20):…”

“…These operations are illustrated in figure 2. Many measurements have been made and treated using the first method (1, 3, 4, 5, 6, 7, 8, 9, 10,11,13,15,16,17,18,19,20,21,22,23). Somewhat fewer treatments by the graphical procedure have appeared in the literature.…”

Simple Centrifugal Filtration Assembly for Preparation of Solid Samples for Radioassay

“…The use of centrifugal filtration not only permits the easy handling of many samples at once (up to 16 samples in a conventional centrifuge equipped with a 16-place head), but also speeds operation in those cases where suction filtration (4) would normally be very slow (as when calcium oxalate is precipitated from serum which has not previously been deproteinized). At the same time it minimizes the danger of losing some precipitate in siphoning off the supernate, as may easily occur in existing centrifugal devices.…”