GAS. 



however, the colour of which it destroys, 

 as that of the red rose. The effect of the 

 gas upon these colours is similar. 



The saturated solution allows the gas 

 to escape at a very moderate heat, and by 

 boiling, the greater part is expeHed, 

 though the liquor remains acid, appa- 

 rently from the presence of sulphuric 

 acid. It is singular that it is not expelled 

 by freezing, but still remains combined 

 with the ice, and renders it so heavy that 

 it sinks in water. Tl)is act shows that 

 that this has, comparatively with others, 

 little tendency to pass into the aeriform 

 state. The freezing of the solution takes 

 place at a few degrees below 32. 



When two parts of the gas are mix- 

 ed with one part of oxygen gas, if the 

 mixture is kept over mercury, they do not 

 act on each other. But if a small portion 

 of water is introduced, they gradually 

 combine and form sulphuric acid, a fact 

 explained by Mr. Murray, on the suppo- 

 sition that the water exerts a strong dis- 

 posing affinity to this acid, or, to speak 

 more intelligibly, according to the expla- 

 nation of disposing affinity given under 

 our article CHEMISTRY, the water at- 

 tracts the sulphurous gas, and, by de- 

 priving it of its state of elastic fluidity, 

 renders it capable of more readily uniting 



with the oxygen, which is also effected 

 by a like action of the water; and as 

 these combine into sulphuric acid, which 

 is more soluble than the sulphurous, the 

 process is still more facilitated, and goes 

 on progressively until the effect is com- 

 pleted. By passing s mixture of oxygen 

 gas and sulphurous acid gas through a 

 tube heated to redness, they instantly 

 combine, and sulphuric acid is formed. 



This acid combines with facility with 

 the alkalies, forming salts denominated 

 sulphites, which differ considerably from 

 the salts formed by the sulphuric acid. 

 Their taste is sulphurous ; they are de- 

 composed by a high temperature, their 

 acid being either expelled, or a portion 

 of sulphur being driven off, in which case 

 they become sulphates ; they are also de- 

 composed by the greater part of the 

 acids, and then the sulphurous acid is 

 disengaged with effervescence. The al- 

 kaline sulphites are more soluble than 

 the sulphates in water, the earihy sul- 

 phates less so. All these salts are con- 

 verted into sulphates by exposure to the 

 atmospheric air, or by the action of any 

 snbstance capable of affording them oxy- 

 gen. They suffer this change, for exam- 

 ple, by deflagration with nitre. See SUL- 

 PHUROUS ACID, 



