HYDROCHLORIC ACID. 295 



unites with the hydrogen of the acid,* forming hydrochloric 



acid gas, or spirits of salt, which passes away in the shape 



of a white smoke. That is to say, it would so pass away if 



it were allowed to escape, and it did pass away at one 



time, to the annoyance and injury of all who lived near the 



factories, for the fumes are very powerful, and not only 



destroyed trees and grass and every green thing in the 



neighbourhood, but ruined the farmers and gardeners for 



some distance. Then taller chimneys were built to carry 



the fumes higher up, and so they did ; but the gas was not 



destroyed, and simply came down again a little farther off 



than before, but with equally disastrous effects. This kind 



of thing, of course, could not be allowed to go on, and the 



next plan tried was turning the gas into the canals, where it 



was speedily absorbed by the water. But then there soon 



arose another outcry, for the people who owned barges 



complained that the gas made the iron rivets and nails 



come out of their boats. Finally, instead of being allowed 



to pollute the air or the canals, the gas was collected in a 



small quantity of water, and the Alkali Works Act was 



passed, compelling the manufacturers to condense it all and 



not suffer any to escape. And then it was discovered that 



this noxious matter might be converted into a valuable 



servant. 



Hitherto the only way of bleaching known had been by 

 means of the sun and air, but now chlorine gas was found 

 to be a very powerful bleacher, and was made to do the 

 work instead. "By passing hydrochloric gas and air to- 

 gether over heated copper sulphate," the hydrogen of the 



* All true acids contain hydrogen. 



