SILVER 297 



Silver 110'" (270 days) Beta 0.087, 0.53, 2.12, 2.86 Gamma 0.116-1. 51(; 



Cat. No. Sp. Act. Form Cost ( 



Ag-llO-I 5 mc/g AgNO.-i $33/22 nu- 



Ag-llO-P 100-300 mc/g AgNO,-, $l/mc 



Mica W. hit. C. Scint. C. 



2.2 X lO-i 8 X 10-5 4 X 10-* 



Critical Org. 

 Liver 



Intake Levels. It has been estimated that the daily intake of silver in 

 foods amounts to 0.06 to 0.08 mg, and as much as 0.3 and 0.9 ppm have 

 been found in wheat flour and bran, respectively. The biological interest 

 is primarily in the therapeutic use of radioactive silver colloids and the 

 possibilities of detection of abscesses and tumors (Ag-1). 



Radioassay. Preparation Ag-llO-P will probably be preferred when 

 there are no objections to the long half-life. The energies are such that 

 routine beta or gamma counting presents no difficulties. Ag^^ has the 

 advantages of higher specific activity and a shorter half-life. However, 

 there are the disadvantages of radiocontaminants and the fact that pure 

 beta emitters are not usually satisfactory for therapeutic purposes. The 

 Pd^"*^ contribution can be eliminated by decay before the counting of the 

 samples. 



Chemistry. Biological samples may be either wet- or dry-ashed with- 

 out any particular precautions. Silver may be estimated chemically by 

 various colorimetric methods including the use of dithizone. 



Typical Methods. Silver colloids were prepared with Ag'" and paren- 

 terally administered to mice in amounts of 10"' to 10** counts/min (Ag-2). 

 Tissues were dry-ashed at 625 to 650°C, and the ash dissolved in concen- 

 trated HNO3. With samples of low activity and salt content, the HNO3 

 solution was decanted into a seamless tin counting cup, the bottom of 

 which had been layered with concentrated NH4OH to prevent corrosion. 

 With other tissues such as liver and bone, the decantations were made 

 into volumetric flasks, care being taken to keep the solution acid. After 

 mixing, 1- to 3-ml aliquots were taken and transferred to counting cups 

 layered with NH4OH. Transfers from the ashing vessel were made (luan- 



