Conditions were chosen for the batch processing of Athabasca bitumen such that approximately 8% of the feed was converted to solids under an atmosphere of nitrogen. When hydrogen or tetralin was used, the amount of solids formed was cut in half. The combination of hydrogen and tetralin decreased the amount of solids formed by one-half again. These conditions were used to study radical trapping reactions and hydrogen transfer under a variety of conditions using solids formation as a measure of reaction. None of the reagents used decreased solids formation significantly, and many increased the retrograde reaction. Correlations between solids formation (2-25% of feed) and yields and conversions showed that CCR conversion and sulfur conversion were not correlated with solids formation but nitrogen and vanadium conversions were. Most significant was the finding that losses (yields of gases) were constant for the 29 runs, at constant residuum conversion. Gases must be formed as a result of the initial thermally induced carbon-to-carbon bond breaking step in order for the yield to be independent of solids formation. Distillate yields decreased as solids formation increased.