Digital density meter, precision

The use of a precision digital density meter as supplied by Mettler Instruments (Anton Paar, Ag.) appeared attractive. Few references on using density measurements to follow polymerization or other reactions appear in the literature. Poehlein and Dougherty (2) mentioned, without elaboration, the occasional use of y-ray density meters to measure conversion for control purposes in continuous emulsion polymerization. Braun and Disselhoff (3) utilized an instrument by Anton Paar, Ag. but only in a very limited fashion. More recently Rentsch and Schultz(4) also utilized an instrument by Anton Paar, Ag. for the continuous density measurement of the cationic polymerization of 1,3,6,9-tetraoxacycloundecane. Ray(5) has used a newer model Paar digital density meter to monitor emulsion polymerization in a continuous stirred tank reactor train. Trathnigg(6, 7) quite recently considered the solution polymerization of styrene in tetrahydrofuran and discusses the effect of mixing on the reliability of the conversion data calculated. Two other references by Russian authors(8,9) are known citing kinetic measurements by the density method but their procedures do not fulfill the above stated requirements. 

The development of digital density meters (manufactured by the Anton Paar Co., Graz, Austria) has provided convenience and speed of performance, as well as versatility and high precision of measurement. The method used in these devices is based on the determination of the resonance frequency of an electronically excited mechanical oscillator. The oscillator consists of a hollow U-shaped glass tube of precisely defined volume into which the samples are injected by 1-ml syringes. A minimum of about 0.7 cm of the sample of exactly known concentration (about 5 - 20 mg cm ) is required. 

The density of microemulsions and solvents was measured with a Paar digital precision density meter DMA 60 with an external measuring cell DMA 602 (Anton Paar, Austria). An ultrathermostat controlled the temperature at 25.00°C 0.01°C. The accuracy of density measurements was within 5x 10" kg dm". ... 

Density and specific volume of mesophases are measured under atmospheric pressure with pycnometers [17-22], dilatometers [16, 23-25] (e.g., differential scanning dilatometers, DSD [26-31]), with a buoyancy method [32], and with a vibrating device, known as a digital precision density meter system, or densitometer (Anton Paar K.G.) [33-38], Devices for high-pressure measurements of specific volumes have been described by Kuss [39,40] and Ddrrer et al. [41], but were also mentioned earlier [42], More recently, a device for simultaneous... 

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