320 



SULPHUR. 



of one portion of the sulphuric acid, and thereby causes the for- 

 mation of sulphurous acid. Charcoal, chips of wood, straw 

 and such bodies occasion a similar decomposition of sulphuric 

 acid,, when heated with it, but the gas is then mixed with a large 

 quantity of carbonic acid. If the sulphurous acid, however, is 

 to be used to impregnate water, or in making alkaline sulphites, 

 the presence of that gas is immaterial. With that object, a 

 quantity of oil of vitriol, equal in volume to 4 ounce measures of 

 water, which for brevity may be spoken of as 4 ounce measures 

 of oil of vitriol, may be introduced into a flask (see figure) with 



FIG. 36. 



\ ounce of pounded charcoal, and the 

 two substances well mixed with agita- 

 tion. Effervescence takes place, upon 

 applying heat to the flask, from the 

 evolution of gas, which may be con- 

 ducted in the first instance into an 

 intermediate phial, through the cork 

 of which a stout tube passes, open 

 at both ends and about 3-8ths of an 

 inch in internal diameter. This phial 

 contains about an ounce of water, 

 into which the tube dips, and serves 

 the purpose of condensing any sul- 

 phuric acid vapour, that may be carried over by the gas, or of 

 intercepting the liquid material in the flask, if thrown out by 

 ebullition, and also of preventing the liquid in the second bottle 

 from passing back, by the gas tube, into the generating flask, 

 on the occurrence of a contraction of the air in that flask, by 

 cooling or any other cause. When that contraction happens in 

 this arrangement, the external air enters the intermediate phial 

 by its open tube. The second bottle is nearly filled with the 

 liquid to be impregnated by the gas. This is the form in most 

 frequent use of the Wolfe's bottles, employed in transmitting a 

 stream of gas through a liquid. 



Water at 60 is capable of dissolving 37 times its volume of 

 sulphurous acid, which makes it necessary to collect this gas for 

 examination in jars filled with mercury in the mercurial trough, 

 and not over water. Its density is 2210.6, and it contains 2 

 volumes of oxygen with l-3rd of a volume of sulphur vapour, 

 condensed into 2 volumes, which form its combining measure. It 

 may easily be obtained in the liquid state by transmitting the dry 



