HOSTETTER AND SOSMANI MERCURY STILL 13 



After several such exasperating experiences with glass stills — 

 the overheating being caused by rising voltage on the power 

 line — we had our still remade of silica glass (fused quartz, or 

 "quartz glass"), and it has been in use more or less continuously 

 for several years. The additional cost of the silica-glass still is 

 well expended in the insurance thereby secured against inter- 

 ruption of the distillation. We have been requested to put on 

 record a brief description of the still, having had a number of 

 inquiries for information concerning its design. 



Design of the still. The construction is shown in detail in 

 figure 1. An effort has been made to simplify the still as much 

 as possible in order to minimize the difficulties connected with 

 the working of silica . glass. No originality is claimed for the 

 design : an inspection of the diagram will show that the essential 

 points of any continuously acting still have been embodied, 

 some having been taken from one still and some from another. 



The distillation chamber (D) has an inside diameter of 30 mm. 

 and a length of 110 mm. The condenser (C) has an inside 

 diameter of 13 mm. Both of these parts of the apparatus are 

 made of the semitransparent inexpensive variety of silica glass. 

 The smaller vertical tubes, A and B, however, are made of the 

 transparent variety, thus enabling one to observe readily the 

 rate of condensation and to see whether the vacuum is being 

 maintained. At V the still is connected to a suction pump 

 that gives a pressure of 1 cm. of mercury or less. This joint is 

 made with hard De Khotinsky cement and is located where it 

 will be air-cooled as thoroughly as possible. The lengths of the 

 small vertical tubes must be such that at ordinary atmospheric 

 pressure the distillation chamber is about half filled: the length 

 of A is 720 mm. to the bottom of the distillation chamber, while 

 B has a length of 840 mm. The inside diameters of A and B 

 should not be too small; the tubes on our still have a bore of 

 3 mm., but 5 mm. might be better. 



The fu7'nace. The furnace is wound so as to go directly on 

 the 110-volt circuit (alternating or direct current) without any 

 external resistance. The power consumption is about 60 watts. 

 Since the temperature required is comparatively low, various 



