Selected minor element chemical analyses of manganese nodules and crusts from the Indian Ocean

Ferromanganese nodules and encrustations have been analysed for selected minor elements (mainly Cd, Cr and Ti) by atomic absorption spectrophotometry. The preparation of ferromanganese-oxide samples for analysis varied according to the nature of the samples. Those covered by adhering sediment were washed clean with de-ionised water and left to dry but in some cases this treatment was not necessary. Where possible, 10 to 15 g. of sample was taken for crushing. Preliminary dessication procedure was required for ferromanganese-oxide samples, because of their tendency to absorb atmospheric moisture when in a finely divided state. After 2 ml. of 6M HCL had been added to the beakers, they were placed on a hotplate and heated gently for about 2 hours to breakdown the Mn oxides prior to the addition of the main reagents. All the elements investigated were analysed in all samples by atomic absorption spectrophotometry using a Perkin Elmer 403 spectrophotometer.