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[求助] 求翻译，两段文章

1.MOST tracer studies necessitate the synthesis of isotopically labelled materials and the last few years have seen important developments in this branch of radiochemistry. It therefore seems appropriate to survey tJhe methods used for the synthesis of organic compounds labelled with isotopes of the more important elements, viz., hydrogen, carbon, nitrogen, oxygen, sulphur, phosphorus, and the halogens.
2.A neutral aqueous solution of cyanamide, or a solution made very slightly alkaline with ammonia, is evaporated a t reduced pressure to a concentration of a t least 20 per cent cyanamide. While the solution is still hot (70" C. or there-about), ammonia, either gaseous or in the form of aqua am-monia, is added in quantity sufficient to bring its concentra-tion within the range of 2.0 to 4.5 per cent. The tempera-ture is then raised as rapidly as possible until the reaction mixture boils vigorously, and the heating is continued until the cyanamide has been completely converted, as shown by a qualitative test with ammoniacal silver nitrate. The am-monia may be recovered and stored for use in subsequent batches or it may be found desirable to pass it directly into one or more converter units in series, before final recovery. The charge may be evaporated practically to dryness with-out loss or decomposition.

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