JOURNAL OF CHEMICAL EDUCATION
F. 1. REITHEL University of Oregon, Eugene, Oregon
A L ~ o ~theGtechnique H of drying materials in the frozen state has been in use for some time, it has remained largely a research procedure. This is due in part to the fact that the apparatus commonly used, such as that described by Campbell and Pressman,' is relatively costly since its fabrication requires the skill of an expert glam blower. The author feels that many protein and enzyme preparations made in' biochemistry and biochemical preparations courses are well worth preserving, and the following apparatus was c~nstructedto meet the need for a simple and relatively inexpensive freeze drier. The accompanying sketch is largely self+explanatory although a few details are worth noting. The number 13 rubber stopper a t the top was bored with a piece of iron pipe turned down to the proper dimensions. The outlet tube running through the bath of alcohol and dry ice acts as a safety trap, although in practice the ice laye: on the cold finger rarely reaches half way to the outlet. The ring neck of the 500-ml. boiling flask was removed just below the ring- before insertion into the stopper. The procedure used was the following. The inner tube was half filled with ethanol and dry ice was added until excessive ebullition ceased. During this time 50 to 100 ml. of protein solution was poured into the 500ml. flask (inserted in the stopper) and frozen in a thin layer on the walls by rotating in an alcohol-dry ice bath until a slight snapping sound was heard. The stopper bearing the flrssk was then inserted firmly into the large tube and the vacuum of a Cenco Hyvac pump applied. ' CAMPBELL. D. H., AND D. PRESSMAN, S c h c e , 99,285 (1944)
Although the stoppers did not allow the attaining of the best vacuum of which the pump was capable, yet the performance was quite satisfactory. For example, 50 ml. of a 2 per cent protein solution was dehydrated in three houm. .
.
.
BOILING F L S K
