Considering the results obtained in the preceding paper, the pyrrhotite, mesh of which is 28\u27\u27～32\u27\u27, was roasted at 700℃ using a baby rotary furnace, and from the roasting gases sulfuric acid was made by the contact process. Finally, the following results may be stated : - 1. As for our contact process for making sulfuric acid, the most favourable conditions are as follows : - (1) The sulfur dioxide concentration is 7～7.5%. (2) The temperature of catalyser is about 440℃. 2. The pyrrhotite cinders, which are obtained in roasting 75～120g. of ores (28\u27\u27～32\u27\u27) for 30～48 hours at 700℃ in a baby rotary furnace, contain residual sulfurs, which amount to 0.2～0.4%, and are sufficiently available for iron making
