IN POPULAR UHEMISTKT. 67 



38. What would be the volume of the O of Question 16 

 tit 2O* C. and 75O nun. ? 



1.55 293 760 



39. How much KCIO S must be employed to maize an 

 amount of O which shall measure 1OO liters at 18 C. and 

 7<>O mm. ? 



First find how many liters of O under standard conditions 

 wo aid be expanded to 100 liters at 18 C., the given pressure, 

 760 mm., being itself standard. Call the result V. It is 



273_x_100 

 ~291 * 



Each of these liters weighs 1.43 grams ; hence, the total 



weight is 



27,300x1.43 



291 



Let x = the required weight of KC1O 3 . 

 Then 3 : KC1O 3 : : W : x. 



27,300x1.43 

 48: 122.5:: -- ^_ - : x. 



Hence, _ 27,300x1.43x122.5 



~291x48 



x = 342.4 grams. 



371. Hoiv could you detect any free O in ajar ofN? 



By passing into it some NO (see p. 34). It will combine 

 with the free O, forming red fumes of NO a . 



2. Hoiv would you remove the product of the test ? 



By allowing the mixture to stand over water, which will 

 dissolve the NO 2 . 



3. In the experiment shown in Fig. ,9, why is the gas 

 red in the flask, but colorless when it bubbles up into the 

 jar ? 



