Abstract
The preparation of water of sufficient purity for critical biological work, and in sufficient quantity, is a perennial problem in biological research laboratories. It is generally agreed that the output of metallic stills such as those of block tin is likely to prove unsatisfactory. Quartz is expensive and the units ordinarily available have a low output and require constant attention. Pyrex glass has proved a satisfactory substitute for most work and there are many types of Pyrex stills available which give excellent results as to quality of product. Most of them, however, are far from automatic and are generally likewise of rather low output. The type of all-Pyrex still described here has been developed after considerable experience, and has been used successfully in preparing nutrients for tissue-culture studies in a number of laboratories. It is relatively inexpensive, and once set up requires a minimum of attention.
The outfit as we use it (Fig. 1) consists of two duplicate units, each made up of 4 items, 3 of which are standard. The units are 1) a standard stove-type heater, usually a 2-burner electric stove with 3-heat burners; 2) two standard flat-bottomed 2-liter distilling flasks (Fig. 2. 3) each with 34/45 ST female joint at the top and side-arm having a 24/40 ST male joint; 3) two standard 22 cm Fried-rich condensers, each with a 24/40 ST female connection at the top and standard drip point below, and 4) two constant-level inlet tubes. The inlet tubes∗ consist of 5 pieces (Fig. 1, 2, 3): first a) there is a feed unit consisting of a 34/45 ST male joint attached above to a 30 mm tubulation and below to one of 20 mm diameter.
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