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LECTURES TO SCIENCE TEACHERS. 



flame, and the products of the combustion, the fumes of 

 sulphur dioxide, (SO 2 ), pass, together with excess of air, into 

 the large glass globe. So far, then, we have, as you see, 

 no formation of suluhuric acid or white fumes. Now, how- 



FIG. 3. 



ever, I pour some nitric acid upon the copper contained in 

 the small flask (a), and thus I evolve some nitric oxide gas, 

 which passes into the globe along with the sulphur dioxide ; 

 at the same time I boil the water contained in the flask (6), and 



