A simple high capacity freeze-drier for histochemical use

Summary A new freeze-drier for histochemical use is described. It uses a refrigerated cooling bath for outer cooling and large amounts of phosphorous pentoxide as water vapor trap.The main features are a very high drying capacity, a simple, reliable easy-to-handle construction and a series of safety devices which, including a rigid stainless steel vacuum chamber which cannot implode, ensures reproducable results.Estimations of relative dryness can be performed during drying. An extra blind flange entrance to the vacuum chamber and the use of standard vacuum connections makes the apparatus versatile. Thus it can be used also for chemical freeze-drying.The apparatus was developed for use with the Falck-Hillarp fluorescence technique for histochemical visualization of monoamines. It gives excellent results with this technique both with peripheral tissues and brain tissue. As many as 20–25 whole brains from adult rats can be processed simultaneously within 3 days.