8 



Operations used in Quantitative Analysis [9 



the gas passes. Thus after a while the temperature of the bath 

 becomes constant. This constant temperature may easily be 

 altered by sliding the tube b in or out of the bulb tube. If 

 slid in, the gas supply is decreased, and vice versa. 



Exercise III.— Weigh out 

 about i gram of barium chloride 

 as before, and heat in the air 

 bath at 120 C. until of constant 

 weight. Calculate the percent- 

 age of combined water as in 

 Exercise II. 



EVAPORATION OF 

 LIQUIDS 



9. In quantitative analysis 

 it is usual to evaporate liquids 

 at a temperature just below their boiling-point. This prevents 

 loss by spirting. Figs. 7 and 8 show convenient forms of 



Fig. 7.— Water Bath. 



Fig. 8. 



water bath, though should the bath be kept in work con- 

 tinuously it will be necessary to have some attachment to 



