1. Sized products of the lead concentrate are briquetted, polished and analized statistically under the microscope. Mineral composition, and "free" and "locked" relationships of each mineral have been determined. From the result obtained, it has been concluded that to improve the grade of the lead concentrate it is necessary. to depress the "free" sphalerite and pyrite more effectively, because these minerals are in part flótated unduly in the lead circuit as "free" grains, not locked with galena. To improve the recovery, it is advisable to avoid overgrinding which increases the loss in grains of slime size.
2. Distribution of the silver in each base metal sulphide has been determined by dithizon. The most important silver carrier is galena, and some of the galena grains which are more argentiferous than others include minute specks of silver sulphoantimonide such as pyrargyrite and polybasite. Sphalerite and pyrite are also argentiferous, so it is impossible to concentrate all the silver by improving the lead concentrate from which silver is recovered.