Abstract: The invention relates to an ultrasonic resonator cell, comprising: a cell body having first and second opposite end faces forming at least one sample cavity extending between the end faces for receiving a sample to be investigated, a first electro-acoustical transducer wafer, a second electro-acoustical transducer wafer, a first end piece, a second end piece, and at least one fastener for applying axial pressure on the first and second end pieces for fastening the first and second electro-acoustical transducer wafers to the cell body on the respective end face of the cell body.

Abstract: The invention relates to a cell for measuring acoustical properties of a fluid sample comprising cell body having first and second opposite substantially flat end faces and forming at least one sample cavity for receiving a sample to be investigated and first and second electro-acoustical transducer wafers each having first and second main surfaces, said first main surface of said first and second transducers being positioned at said first and second end surfaces respectively, of said cell body. The invention proposes to provide at least one sealing means at one end face.

Abstract: A method of determining a phase separation concentration of a sample substance in a solution, comprises the steps of measuring values of a physical quantity of the solution containing the sample substance with at least one sample substance concentration lower then the phase separation concentration, wherein the physical quantity characterizes an interaction of the solution with sound waves, determining a concentration function representing a dependency of the physical quantity on the sample substance concentration lower then the phase separation concentration, and determining the phase separation concentration as a concentration value at which the concentration function equals a predetermined critical value of the physical quantity of the solution containing the sample substance in a saturated condition. Furthermore, a concentration determining device is described.

Abstract: The invention provides a method for determining optimal concentrations of additives which are capable to protect sensitive biomacromolecules, e.g. proteins or nucleic acids, against denaturation and aggregation in a solution comprising at least one species of a biomacromolecule and at least one species of a protective additive comprising: a) treating said solution with ultrasonic waves; and b) recording the value of one or more ultrasonic parameters, such as the ultrasonic velocity in said solution and/or the ultrasonic absorption of said solution. The above method allows to detect critical changes of the ultrasonic parameter dependent from the concentration of the protective additive and indicative of interactions or changes of interactions between additive and biomacromolecules and/or between different biomacromolecules and/or changes of the conformation of the biomacromolecules.