SMALL TISSUE DRYERS WITH HIGH CAPACITY FOR RAPID FREEZE-DRYING

In close connection to the development of a new histochemical technique the need for a small high capacity freeze dryer greatly increased. A convenient system was devised, which allows work with several independent drying chambers simultaneously. The cooling source is a standard refrigeration plant equipped with an expansion coil in a Dewar flask from which cold liquid is distributed to the separate drying units. The specimen carrier of each unit can take about twenty tissue pieces. Even though diffusion pump, cold finger trap, and other delicate components have been avoided, drying time is quite favourable; it may be as little as five hours for pieces of standard size. Moreover, the evacuation pump is well protected against vapor. The freeze dryer is built mainly of standard components or inexpensive modifications of these.