The densltles of 1,2-butan.dlol, 1,3-butanedlol, 1,4-butan.dlol, and 2,3-butan.dlol were measured at atmospheric pressure and at temperatures ranging from 299 to 463 K wlth an accuracy of f0.2 % . VlsccOrlu.8 of the same butrrndldt were measured between 293 and 423 K wHh an edbn8I.d accuracy of f 1 % . The low-temperature results for both denelty and viscosity wore found to be In good agrwnent wHh data reported In the literature.
IntroductlonIn recent years, considerable attentlon has been paid to the design of absorption heat pumps and refrigeration equipment using a variety of working fluids. These working fluids include aqueous solutions of lithium bromide and mixtures of ammonia and butanediols (7). Since accurate values of thermophysical properHes are indispensable for reliable design, we have measured the densities, viscosities, and thermal conductivities of several systems of interest in absorption refrigeration over a wide range of temperatures (2-4). The thermophysicai properties of concentrated lithium bromide solutions were reported in our prevkus publications ( 3 , 4). The densitleg and viscosiis of 1,2-butanediol, 1 ,3-butanedlol, 1 A-butanediol, and 2,3-butanediol are reported in this work. Literature data on densities of butanediols are limited to ambient conditions, whereas viscosity data for these liquids were found to be virtually nonexistent. The purpose of this work was, therefore, to measure new data and to extend the available data on butanediois to higher temperatures.The study of the isomeric butanediois is also impottant from a fundamental point of view because it allows us to examine in detail the influence of the spacing of the OH groups on the thermophysicai properties of the butanediois.
Experlmental Sectlon
Mat&&.The liquid samples used in the present work were obtained from Aidrich Chemical Co., Inc., and were used without further purification. According to the supplier, the purities of the materials were 98% for l,Bbutanediol, better than 99% for 1,3-and l,Cbutanediols, and 99% for 2,3-butanedioi. In the case of 1,3-and 2,3-butanediols, which are hygroscopic, the water impurity was as low as C0.005 % .
DendtyMeaurremenfs . Densities were measured using a high-pressure pycnometer designed for pressures up to 10 MPa and temperatures up to 473 K. The principle of operation of this pycnometer and its complete description have been given in a previous paper (2). Only a brief outline and a few remarks about the measurements are given below.The high-pressure pycnometer consisted of a stainless steel cylinder and an isolation valve connected via steel capillary tubing to a high-pressure system. The pycnometer was placed into a fitted aluminum vessel with thick walls H i , in turn, was immersed in a constant-temperature bath containing silicone oil. This arrangement provided sufficient thermal contact, while avoiding the wetting of the outside surface of the pycnometer by the silicone oil. The pycnometer was filled with the fluid to 0021-9568/92/ l737-Q246$O3.00lO
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