Science and research. Studies of non-coking coals. V.F. Parry, supervising engineer of the Golden, Colorado field station of the U.S. Bureau of Mines is "sighting a coke bubble." This procedure is used to determine if a given coke has changed its properties or it is similar to another coke. One gram of powdered coal is heated at 820 degrees centigrade for two and a half minutes. The resulting "bubble" is then compared with a standard chart to determine its characteristics, as revealed by the shape it has assumed. This research is part of a project to find ways of improving the quality of coke from western coal. Sourced from the Library of Congress.