The primary aim of this master thesis is to take a high pressure thermogravimetric analyser (HP-TGA) into operation. For that purpose, some parts of the HP-TGA had to be modernised or fully substituted. For instance, it was necessary to design and build a new moistening device for humidification of the operating gases. In a further step, the whole measuring and control system was renewed. The new user-friendly configuration, which is PC-based, enables a fully automatic running of experiments with defined conditions. After putting the HP-TGA into operation, a series of trials was carried out to test the applicability of that apparatus for scaling and reduction experiments under various conditions. The experimental results allow the definition of optimal operating conditions with regard to adequate flow rates of testing and purging gases, the appropriate sample weight and the best suited purging gas. Scaling experiments show that the HP-TGA is only conditionally suitable for this kind of experiments. The mass increase of the sample during scaling is too small to show a difference on the generated signal. The main results of the reduction experiments with hydrogen as reducing gas show that it is possible to detect the weight loss as a consequence of a reduction process. Accordingly, there results a good suitability for carrying out reduction experiments under various conditions on the HP-TGA.