The Chinese test om march 18, 1972 spread a large amount of hot particles. The variations in activity and nuclide composition with size and colour is studied with the help of reversal autoradiography combined with y-spectrometry. Especially masschain 95 was found to vary highly with colour, colourless particles having the highest content. The average B-activity of the particles in the range 0.7 - 3.5 um is 0.19 Bq/um3. Studies of the fractionation show how active nuclides are incorporated in the hot particles (they contain e.g. 80% of the totally released amount of mass-chain 95 but only 2% of mass-chain 103/Ru/). The inactive content of the fire ball is estimated to 13 kg construction material (iron and/or aluminum) per kt explosion power.