PREPARATION OF A CARRIER-FREE 113Sn SOURCE H. S O M M E R
11. Physikalisches Institut der Universitiit Heidelberg Received 14 March 1968
The laaSn, resulting from a (d,2n)-reaction of 1131n, was separated from the indium by means of fractional distillation. The specific activity of the l~aSn source is at least 180 Ci/g In. Electron spectroscopy requires very thin sources to keep inelastic electron scattering at a low degree. The 113Sn ' usually produced by irradiating tin with neutrons in a reactor, is not suited for electron spectroscopy because of the great amount of inactive tin, which can be separated from 113Sn only by a mass separator. In this case, ll3Sn results from a (d,2n)-reaction of l13In. About 200 mg of natural indium-(III)-oxide*, which contains 4.3% of 113In-oxide, were irradiated with deuterons for 14 h (current 2.8 #A). While being irradiated the indium-oxide was wrapped in Mo-foil (10#m) and cooled by water. The 1138n, produced by irradiation as described above, had an activity of 15#Ci. As a by-product of this irradiation we get - by a (d,p)-process - 114rain, which can be used as a tracer for the separation of the tin from the indium. The activity of the lx4~"In amounted to about 35 #Ci. The irradiated indium-oxide was dissolved in 5 ml HCI. By bubbling chlorine through the solution for 10 h, the indium was oxidized to indium-(III)-chloride and the tin to tin-(IV)-chloride. In this oxidation state tin can be separated from indium by fractional distillation of the chlorides because the boiling points of tin and indium differ considerably (SnC14, mp-36.2 ° C, bp-114.1 ° C; InCl 3, mp-586 ° C). The melting points of eventual complex compounds of tin are very low too ( H 2 [ S n C I 6 ] ' 6 H 2 0 , mp-19.2°C; S n C L ' 5 H 2 0 , mp-
may have been between 80 and ll0°C.) Tube II was cooled by an aluminium rod reaching into a dewar flask, which was filled with liquid nitrogen. The distillation lasted for 35 h. During that time the liquid nitrogen was refilled automatically. The distillate in tube II was redistilled for 25 h. Each distillation caused a loss of about 30% of the active ll3Sn. To the second distillate 0.2 ml H N O 3 and 0.1 ml HC1 were added t. This solution was evaporated in a hole (diameter 3 mm) on a small teflon plate to a volume of about 6 m m 3. With a special pipette this solution was put drop by drop on the foil of the source holder where it was evaporated to dryness. The source has a diameter of about 1.5 ram; its activity was 2.2#Ci. The source was covered with a thin foil of about 15 #g/cm 2 made out of polyvinylformal +. After the very first distillation it was impossible to detect with a NaI-scintillation counter any 7-radiation emitted by 114rain in the distillate. The statistical error of the measured 7-spectrum led, if compared to tin, to a depletion factor for indium of at least 1.6 x 10 3, which corresponds to a total depletion factor greater than
The fractionating still is shown in fig. 1. The filtrated solution first was almost completely evaporated in a small teflon tube. After the evacuation of the two teflon tubes I and II (fig. 1) with a water jet p u m p the tin(IV)-compounds were distilled from tube I into tube II while being heated with a 250 W infrared lamp. The distance between the lamp and tube I was about 4 cm. (The temperature of tube I could only be estimated and
* Purity 99.999~, supplied by Fa. Schuchardt GmbH, Mtinchen, Germany. t HNOa suprapur and HC1 suprapur supplied by Fa. E. Merk AG, Darmstadt, Germany. + Polyvinylformal FM, supplied by Fa. Farbwerke Hoechst AG, Frankfurt-(M)-Hoechst, Germany.
lo 2,0~r= Fig. 1. Fractionating still.
2.5 x 106. The impurity of the ~laSn-source, caused by indium, amounts therefore to less than 1.2x 10-Sg, which correspond to a specific activity of more than 180 Ci/g In. Further experiments which attempted to separate the active tin from indium by means of dithizone, cupferron or an ion exchanger did not lead to satisfactory results. My special thanks are due to Prof. O. Haxel for
continuously supporting this work. I am greatly indebted to Dr. G. Schatz and F. Schulz for irradiating the indium-oxide at the cyclotron laboratory of the Kernforschungszentrum Karlsruhe, Germany; also to Dr. K. Knauf for help with the preparation of the source. This work was financially supported by the Bundesministerium ftir wissenschaftliche Forschung, Germany.