CHLORINE. CALCULATIONS 



141 



cent. But all the four substances are gases (in the hot tube), 

 and mix perfectly. 



The results here noted are interesting, because they show that, 

 under the conditions of the experiment, oxygen is somewhat more 

 active than chlorine in combining with hydrogen. The precise 

 proportions of the four gases present at equilibrium depend on 

 the temperature at which the experiment is carried out. In the 

 commercial application of Deacon's process, this is near 345. 



Preparation from Hydrochloric Acid and an Oxidizing 

 Agent. The best way to make a supply of chlorine in the 

 laboratory is to place potassium 

 permanganate crystals (KMn0 4 ) 

 in a flask (Fig. 49) and allow 

 concentrated hydrochloric acid, 

 previously mixed with an equal 

 volume of water, to fall upon 

 them drop by drop. The gas 

 is rather soluble in water, and'is 

 best collected by displacing the 

 air from bottles. When one 

 bottle is full, it is stoppered 

 and a fresh one substituted. To 

 avoid the escape of the very irritating gas into the room the tube 

 from the collecting bottle dips beneath sodium hydroxide solution. 



The essential feature of this reaction is that the oxygen of the 

 potassium permanganate unites with the hydrogen of the hydro- 

 chloric acid to give water. The potassium and manganese take 

 as much chlorine as they require to form their chlorides, KC1 

 and MnCl 2 . The rest of the chlorine is liberated. 



Skeleton: KMn0 4 + HC1 - H 2 + KC1 + MnCl 2 + C1 2 . 



To convert all the oxygen of the KMn0 4 to water, we re- 

 quire 8HC1. The formation of KC1 and MnCl 2 uses up 3 of the 



FIG. 49 



