66 



Conductivity of Aqueous Solutions. Part III. 



29. A VAPOR BATH FOR HEATING THE ROTATING BOMB. 



Such a bath is shown in vertical section in fig. 16. It is made from a 

 piece of ordinary wrought-iron water-pipe, 23 cm. in bore and 46 cm. 

 long. At the lower end the diameter of this pipe is reduced and a bottom 

 is welded in. This reduction in the area of the bottom serves to diminish 

 the amount of boiling substance needed. The cover is a thin plate of sheet 

 iron having the edge rolled over, and sets into a groove in the top of the 

 bath, this groove being formed by shrinking an iron ring of L-shaped 

 cross-section onto the upper end of the pipe, which has previously been 

 turned true on the outside for a short distance. The cover is sealed by 

 pouring some melted Rose metal into the groove. After an experiment 

 the cover can be raised a little out of the melted metal shortly before it 

 solidifies, since the temperature of the bath is then so low that but little 

 vapor would escape, even if the cover were completely removed. 



As in the earlier 

 heaters, a loose roll of 

 copper or iron gauze 

 is placed in each of 

 the condenser tubes, 

 and, to increase still 

 further the efficacy of 

 these condensers, a 

 spiral of small tubing, 

 either of lead or seam- 

 less copper, is wound 

 tightly around each 

 of them and water 

 is circulated through 

 these spirals. 



The cylindrical iron 

 shield used in the 

 earlier vapor baths, 

 designated by Q in 

 fig. 2, Part II, is, for various reasons, undesirable in the present bath 

 and has been shown to be unnecessary, provided the outside of the 

 bath is sufficiently protected from radiation. JV is a conical shield of thin 

 sheet iron, which is supported by three short iron rods riveted into the 

 cover, and keeps the condensed liquid from dropping onto the bomb. 



The eccentric-rods for rotating the bomb extend out through iron chim- 

 neys a and b, which are brazed into the cover. A little cotton stuck in 

 the ends of these chimneys prevents almost completely the escape of vapor. 

 The thermometer is similarly introduced through the chimney c. Of the 



Fig. 16. 



