Chemical composition of manganese nodules from GH80-1 cruise

67 samples of manganese nodules were obtained during the GH79-1 Cruise of R/V Hakurei Maru in the northern part of the Central Pacific Basin. All nodules were immersed in running water and then ion-free water. After air-dried, samples were ground to under 150 mesh. The ground samples were encased in small paper bags, dried at 20-25°C for 24 hours, and then kept in a desiccator. In most cases an analysis was done for mixed ground sample of two or three different size classes of nodules from each box corer or freefall grab. Mn, Fe, Ni, Cu, Co. Pb, and Zn were determined by atomic absorption spectrometry. Each sample of 0.1 g was decomposed with a mixture of 5 ml of hydrochloric acid and 5 ml of nitric acid in a covered 50 ml beaker on a boiling water bath for about 30 minutes. After cooling, the solution was filtered into a 100 ml calibrated flask and diluted to the mark with water. The atomic absorbance of each element in the sample solution was measured using an atomic absorption spectrometer using an air-acetylene flame.