Abstract
Six kinds of Japanese coals-Taiheiyo (77.8%C), Bibai (81.1%C), Akabira (83.4%C), Yubari (86.2%C), Hashima (87.2%C) and Nishikawachi (89. 8%C) were heat treated at the temperatures from 600 to 900°C and the yields of products, proximate and ultimate analyses including helium densities of the heat treated coals were investigated.