A novel pycnometer has been designed for density measurements at elevated temperatures (up to T = 473.15 K). The pycnometer consists of a stainless steel cell connected to a small-bore tube. The main feature of the design includes a bored-through expansion fitting, which allows the overflow due to thermal expansion from the cell (via the small-bore tube) to collect in a pressurized line. Densities were measured for pure 1-butanol, pure n-heptane, and for mixtures {x(b)CH(3)(CH2)OH + (1 - x(b))CH3(CH2)(5)CH3}, from T = 316.85 K to T = 458.15 K, at a pressure of 4.93 MPa. Excess volumes were calculated and reported for these mixtures. (C) 2003 Elsevier Ltd. All rights reserved.