SULPHURIC ACID. 69 



ined, it will have a suffocating odour and an acid 

 taste. 



Sulphurous acid, or the vapour of burning sul- 

 phur, has been found very useful for destroying 

 the infection of clothes and small uninhabited 

 places, and for fumigating letters from contagious 

 places. It is used in dyeing, and for whitening 

 straw and silk. 



Sulphuric Acid* 



This acid is composed of sulphur and oxygen, 

 and contains a greater proportion of oxygen than 

 sulphurous acid. 



This acid is the same with that commonly known 

 by the name of 'Oil of * Vitriol. It was so called ori- 

 ginally, because it was procured from green vitriol; 

 now called sulphate of iron. 



Common oil of vitriol has strong acid properties. 

 It is of an oily consistence, and has usually a brown 

 tinge, from impurities. It is inodorous, and about 

 twice as heavy as water. It is highly corrosive, 

 acting strongly on vegetable and animal substances. 



It attracts water very strongly, and cannot be 

 entirely separated from it by any known process. 

 When exposed to the air, it attracts the watery 

 vapour in the atmosphere, so a& to increase rapidly 

 in weight, which will be doubled in a month. If 

 mixed with cold water, it suddenly becomes ex- 

 tremely hot, even more so than boiling water; and 

 on this account, when it is necessary to dilute it 

 with water, this should be performed very gradually. 

 Sulphuric acid is now made by burning sulphur 

 mixed with nitre, in close chambers, entirely lined 



F 3 



