T H. NORKIS
l7Ol.
74
[CONTRIBUTION FROM THE CHEMISTRY DEPARTMEN1 O F OREGON STATE COLLEGE]
A Gas-Sample Counting Method for Soft (?-Emitters1 RY
‘r. 11. N O R R I 5
A simple, rapid and accurate gas countiug method for soft 6-emitters iuch volves the use of a sample holder independent of the G-?I1 counter.
In the course of work in this Laboratory with S”-labeled sulfur dioxide, it has been convenient to develop a method for gas counting in order to avoid the labor of preparing solid counting specinieus. The method, which would be equally applicable to C14 counting (say as carbon dioxide), appears to have certain original merits as compared with other r e p ~ r t e d ~gas , ~ counting techniques for soft $emitters and is therefore being reported here. ;\part from its expeditiousness, gas counting is probably capable of yielding greater precision than solid-sample counting. As has been pointed out by Freedman and Hume4 precision results cannot normally be obtained from the counting of 0emitters in solid form, because of irreproducibility of self-scattering and self-absorption effects. this
6 capillary
cork wax
Fig. 1.-Gas
sample holder filling assembly
(1) Published with the approval of the OregonState College Monographs Committee, Research Paper X o . 192, Department of Chemistry, School of Science. (2) J. T . Kummer, Xucleonirs, 3, KO. 1, 27 (1948). (3) F. Bonner and J. Turlievich, Trirs J O C K K A L , 1 3 , 561 (1981). ( 4 ) A . J. Frrrdmati a n d D T l i i i n i r , ~YrirJj(-tire t o exactly 740 nim. In these operations room temtxrature has been maintained a t 27 i 1’; corrections could, however, be applied as necessary for temperature variation. After filling, B and C are closed and the gas not thus isolated is disposed of into the vacuum system prior t o removal of the assembly a t joint E. Then, in a hood, C is opened arid the sample holder, A, removed from its cover. For counting, the sample holder is placed over an inverted end~vindoxvcounter, the holder and counter windows being very close together. The counter (Tracerlab TGC-2, window 1.7 n i g . j c i u , ~ is ) iiiounted within a female ground joint t o ( ‘ i i < i i r
