264 SMITH'S INTERMEDIATE CHEMISTRY 



a flask with water, violently and continuously, without any appre- 

 ciable solution. When the water is thrown, by the shaking, 

 through the oxygen, the oxygen is split up by the water, and driven 

 about, but the fog particles move with the oxygen, so that the 

 water never reaches them. On the other hand, when the mixture 

 of gases bubbles through 97-99 per cent sulphuric acid, as is done 

 iji practice, there is practically no water available for evaporation, 

 the sulphur trioxide remains gaseous, and its rapidly moving 

 molecules in a few seconds have all plunged into the sulphuric 

 acid and combined with it, either uniting with the 1 to 3 per cent of 

 water present, or, when oleum is made, uniting with the sulphuric 

 acid to form H^O?. 



This case affords an admirable illustration of the importance of 

 physics in practical chemistry (p. 22). The chemical reaction 

 occurs with water, but the physical condition of the fog of sulphuric 

 acid prevents its dissolving and, if water were used in a factory, a 

 large proportion of the sulphuric acid would pass with the excess of 

 oxygen into the air and be lost. In fact, it would kill vegetation, 

 and make life unbearable in the neighborhood. 



Chamber Process for Sulphuric Acid. Although salts of 

 sulphuric acid, such as calcium sulphate CaSO4, are exceedingly 

 plentiful in nature, the preparation of the acid by chemical action 

 upon the salts is not practicable. The sulphates, indeed, inter- 

 act with all acids, but the actions are reversible. The completion 

 of the action by the plan used in making hydrogen chloride (p. 126), 

 involving the removal of the sulphuric acid by distillation, would 

 be difficult on account of the involatility of this acid. It boils at 

 330; and suitable acids, less volatile still, which might be used to 

 liberate it, do not exist. We are therefore compelled to build up 

 sulphuric acid from its elements. 



The gases, the interactions of which result in the formation of 

 sulphuric acid, are: water vapor, sulphur dioxide, nitrous anhy- 



