DEMINERALISATA TERHADAP Cu, Mn DAN Na DENGAN MENGGUNAKAN ANALISA PENGAKTIPAN NETRON. Traces of Cu, Mn and Na had been determined in tap, distilled, doubl y distilled and demineral ised water using the neutron activation anal ysis technique. Both the water sample and the standard are irradiated in a Reactor with a flux of ± 1012n/em 2/sec. for 4 hours and after adding a Cu-Carrier and HCI, Cu is precipitated as CuS by H2S. Mn is precipitated together with the Mn carrier as Mn02 by oxidation with KCI03, of the filtrate from the Cu precipitation. Na is counted in the filtrate from the Mn precipita tion. The radioactivity of each of these elements is analyzed using a single channel gamma scintillation with a solid 21/2 x 21/2 inc, Nal (Thallium activated) crystal which serves as the detector. The double distilled water from a pyrex glass stil, prepared with the addition of KMnO4 and NaOH with the purpose to free pyrogens, shows to contain Mn and Na which are relatively high. There is possibility that these traces of metals are distilled over. The Na content of distilled water, stored in bottles of ordinary alkali glass is rather high which might be due to the leaching of the. bottle. The Cu content of distilled water, from a copper stil is relatively high which is thought to be due to dissolution especially of the copper condenser. TAN BIAUW SOEN, POEY SENG BOUW dan DJALI AHIMSA *) Laboratorium Rodiophormacy, Pusat Reektor Atom Bandung. Penyelidikon ini dibantu dengan grant dari DURENAS.