8] Drying of Solids 7 



Enter the results under those of the last example, thus : 



After dr> ing i. 

 ii. 



iii- • • 



Loss . . . 



The loss is calculated by subtracting the last weighing from the 

 weighing obtained in Example I. 



Multiply this 'loss' by 100 and divide by the weight of acid 

 used ; the quotient will give the percentage of water which has 

 been lost. 



8. For drying at temperatures between ioo° and 200 C, 

 an air oven is used. This is very similar to the steam oven. 

 The space between the inner and outer coatings is occupied by 

 air, whilst through a hole in the top is inserted a thermometer 

 held in position by a perforated cork. 



Should it be necessary to keep this bath at a constant tem- 

 perature for any length of time, some form of regulator may be 

 used. The one represented in fig. 6 

 is both simple and convenient, a is 

 a bulb about f inch diameter, blown 

 at the end of a piece of f-inch glass 

 tubing 5 inches long. An inch from 

 the other end is a side tube (c). b is 

 a piece of copper tube \ inch dia- 

 meter, fitted into the bulb tube by a 

 sound cork. The end of the copper 

 tube D is slit up with a fine saw for 

 about an inch. The bulb is filled 

 with mercury, and the whole apparatus 

 is fitted by a split cork into the top of 

 the air oven, b is connected with the gas supply, and c with 

 the burner which heats the oven. Should the oven become too 

 hot, the mercury will rise and close the slit d through which 



Fig. 6.— Regulator. 



