Considering the vibrating system with spring constant k, the following relation can be established:

With

a simple relationship, T² ∼ ρ, is obtained. This dependence is recorded electronically and stored on an internal data carrier. The data can subsequently be made available to the experimenter using various output devices.

The U-shaped tube is made of borosilicate glass (Duran 50), which is resistant to almost all aggressive substances. The material has another fundamentally important property: its density does not change within the temperature range from 10 °C to 55 °C, so the measurement volume remains constant. The commercial instrument also has its own temperature control and can be calibrated using an internal reference. Problems specific to the nitromethane–pentanol system are discussed in Section 4.8.

4.8 Measurement Procedures for the Nitromethane–Pentanol System

This section briefly describes how the nitromethane–pentanol system was handled in conjunction with the measuring instruments. The instruments used and the modifications made to them are presented in sequence.

1. General

For all measurements in this work, the critical mixture had to be introduced into the measuring chambers while in the single-phase state. Several apparatus-specific solutions are certainly possible. One method that proved highly effective was to use a hot-air gun. By creating a suitably warm environment around the filling tubes and pre-thermostating the apparatus well above the demixing temperature, filling could be carried out without difficulty. All vessels and equipment used must be thoroughly clean. The solution must also enter the measuring cells without contamination by air bubbles. For the resonators, filling must be performed as quickly as possible, but also slowly enough to ensure proper wetting of the transducers despite possible cooling.

Original mathematical notation is preserved in the extracted image assets.