An in-depth analysis of some methodical aspects of applying pseudo-adiabatic calorimetry

•Analysis of sample and bomb uniformity in adiabatic experiment.•Analysis of sample-bomb equilibrium in adiabatic experiment.•Peculiarities of thermal inertia variability when small samples are used.•Effect of the uncertainty of the sample state at the onset on data interpretation.•Novel method for taking into account data of the thermal initiation period of adiabatic experiment. The Accelerating Rate Calorimeter (ARC) - the first representative of the family of pseudo-adiabatic calorimeters - was designed for assessing reactive hazards of chemical processes. Over time the ARC and similar instruments have found much wider applications such as testing of reactive substances, study of reaction kinetics, design of the emergency relief systems. In all these cases precise knowledge about the current state of the sample is required. There are numerous publications regarding the methodical aspects of pseudo-adiabatic calorimetry but many problems are still waiting for the solution. The aim of this paper is to consider in detail the following serious problems: non-uniformity of the system "sample + bomb"; absence of equilibrium between sample and bomb; variability of thermal inertia; uncertainty of the state of reacting system at the onset. The results presented here demonstrate that in many cases the basic assumptions used for interpretation of adiabatic data can be violated and due attention should be paid to the conditions of an experiment that allow it to remain within the applicability limits of the method.