OXYGEN GAS 2i 



same. Carefully note the properties of these products, i.e. 

 the oxides produced, with respect to appearance, odour, 

 solubility, and, if soluble, acidity of the solution. Be careful 

 to enter each observation in the notebook during the progress 

 of the experiment. 



It will be noticed that while heat caused the decomposition 

 of the oxides of mercury and lead, heat was produced when 

 phosphorus, sulphur, charcoal, and iron combined with oxygen. 

 In subsequent experiments, note whether heat is invariably 

 produced when chemical combination occurs. Again, heat 

 appears to promote chemical change, for the oxides were only 

 formed rapidly when the elements had been heated sufficiently 

 to ignite them. Is this observation also general ? 



When iron rusts, increase of weight occurs because the 

 oxygen of the air with which it combines also possesses 

 weight. Is there any definite proportion between the weights 

 of substances which combine together. Determine, for 

 instance, whether red oxide of mercury contains definite pro- 

 portions of mercury and oxygen. 



Construct a hard glass tube as figured, using a blow-pipe for 

 softening and working the glass, and weigh by suspending it to 

 the arm of the balance by a piece of copper or, 'better, platinum 

 wire. Place in the bottom of the tube X y\ 



about five grams of red oxide of mer- ^■■^•^t^^ ^-^O ^ 

 cury, previously heated in the hot water ^y'y^ 

 oven to dry it, and weigh again. The ^^ ^^^ g 

 difference will be the exact weight of 



the oxide taken. Heat till the whole of the oxide has been 

 decomposed, care being taken not to heat the upper portion of 

 the tube, allow to cool, and weigh. The difference in weight 

 between the mercury left and oxide of mercury taken will be 

 the oxygen evolved. Calculate the amount of oxygen combined 

 with 100 parts by weight of mercury. Repeat the experiment 

 till concordant results are obtained. 



Compare the result with the results obtained by other 



