The paper presents a thermodynamic analysis of the removal of an inert gas from the tank using the vapor of liquefied petroleum gas cargo (called cargo tank gassing-up operation). For this purpose a thermodynamic model was created which considers two extreme cases of this process. The first is ‘piston pushing’ of inert gas using liquefied petroleum gas vapour. The second case is the complete mixing of both gases and removal the mixture from the tank to the atmosphere until desired concentration or amount of liquefied petroleum gas cargo in the tank is reached. On the example of nitrogen as inert gas and ethylene as a cargo, by thermodynamic analysis an attempt was made to determine the technical parameters of the process, i.e., pressure in the tank, temperature, time at which the operation would be carried out in an optimal way, minimizing the loss of cargo used for gassingup. Calculations made it possible to determine the amount of ethylene used to complete the operation and its loss incurred as a result of total mixing of both gases.

The paper is a thermodynamics analysis of the removal of any inert gas from the tank using the vapors of any liquefied petroleum gas cargo (called cargo tank gassing-up operation). For this purpose, a thermodynamic model was created which considers two boundary cases of this process. The first is a ‘piston pushing’ of inert gas using liquefied petroleum gas vapour. The second case is complete mixing of both gases and removal the mixture from the tank to the atmosphere until desired concentration or amount of liquefied petroleum gas cargo in the tank is reached. Calculations make it possible to determine the amount of a gas used to complete the operation and its loss incurred as a result of total mixing of both gases.

Correspondence was an essential form of communication in the world of the humanities in the 1960s and 1970s. The letters exchanged between Józef Andrzej Gierowski and Jacek Staszewski exemplify the scholars’ discussion of Saxon times. This collection is at the same time a reflection of the main currents of research on political history and cultural history of the 18th century. Simultaneously, it is a testimony to the struggle of historians with the black legend of the reign of August II and August III.
The article presents the nature of these conversations and the topics discussed by the scholars: an exchange of views on resources in European archives, the reigns of August II and August III, a discussion of the Enlightenment, reviews of subsequent monographs and doctoral theses prepared at seminars in Kraków and Toruń. The correspondence between the two scholars is evidence not only of a shared passion, an interest in the Saxon era, neglected for many decades and marked by a black legend, but also of an intellectual exchange between the two humanists, which in time developed into a friendship.