Abstract: Interfacial phenomena are observed employing an electronically compensated vacuum micro-balance for weighing the specimen mixture under observation. The gas pressure in the vacuum micro-balance is determined by means of a buoyancy element. During the weighing operation the weights of the specimen and of the buoyancy element and also the temperature of the specimen are determined at intervals of 0.1 to 60 seconds. The measured values thus obtained are supplied to converters whereby they are converted into initial values which are computer-readable. The measured values thus converted are stored intermediately in a computer, successive values being compared with one another until 2 to 50 successive values of the weight of the specimen differ from one another by less than 50.gamma. 1 .gamma. means 10.sup.-6 g. The result of this latter specimen weight comparison, together with the values of the gas pressure and of the temperature, is printed out by a printer connected to the computer.