The invention relates to a device for producing corrosive, acidic phosphate melts. The device comprises a gas-tight reactor (1) which is erected horizontally or vertically and which can be heated inductively or using carbon heating elements. Said device is configured for receiving liquid and/or solid starting materials, whereby the reactor wall consists of a granite external wall (24) and an inner glass-carbon layer (22). The invention also relates to a device for producing the phosphate melts.