At the Garpenberg concentrator the separation of copper and lead minerals is performed with flotation. The method flotation uses the minerals surface properties to separate different minerals. By forming slurry, stirring it and blowing air into the slurry a separation is possible. The copper- minerals that are more hydrophobic to their nature will follow the bubbles to the surface of the slurry and form a froth. The froth is removed and with it the copper-minerals. To further the separation, different reagents like collectors or depressants can be added. Collectors render the surface of the mineral more hydrophobic and more inclined to attach to the bubbles. Dichromate is a depressant with the mission to depress the lead in the flotation. The dichromate attaches to the lead-minerals and render them more hydrophilic. The more hydrophilic the lead-minerals are the better the separation. Dichromate performs excellent in the separation but it is a highly toxic substance that is also carcinogenic. Needless to say a safer and less toxic depressant would be preferred. The object of this master thesis was to investigate the depressant dextrin's effect on the separation, and if it would be possible to replace dichromate with dextrin. The dextrin investigation started with design of experiments with the help of the program MODDE. The designed experiment was executed in the proper order and the result from the experiment was analyzed with both MODDE and Excel. A reference experiment with dichromate was also performed in order to be able to compare with the results from dextrin experiments. The results from the investigation compared with the reference experiment gave indications that dextrin may replace dichromate at least in the case of batch laboratory scale flotation.