23 mL, 150 °C, 1200 psig
This is the original acid digestion vessel introduced by Parr in 1969 to provide a PTFE lined metal vessel of simple design and minimum cost that can be used safely for routine sample preparation purposes. Its wide acceptance over the intervening years has proved it to be an excellent design for general digestion procedures in which temperatures and pressures are held below 150 °C and 1200 psig. It can be used occasionally above 150 °C, but at elevated temperatures it becomes increasingly difficult to maintain a tight seal.
This vessel does not have a safety blow-off disc, but it is designed so that the bottom plate will shear out and release the charge if the vessel pressure should exceed 7000 psig. This ‘weak link’ design, while effective in preventing a lateral burst which might injure a bystander, is not an adequate substitute for a safety blow-off disc as provided in other Parr designs. For this reason, the 4745 Vessel is not recommended for experimental procedures in which explosive pressures may be generated.