306 Domestic Science 



14. How may the volumetric composition of water be deter- 

 mined by (a) a synthetic method ; (6) an analytical method ? 



15. The weight of 1 c.c. of hydrogen at C. and 760 mm. bar. 

 i 0-00009 g. What weight of hydrogen would be needed to fill 

 a spherical balloon, 6 metres in diameter, the gas being at a tempera- 

 ture of 12 C. and under a pressure of 800 mm. bar. ? 



16. Devise an experiment in which it is shown by direct weighing 

 that hydrogen is much lighter than air. 



17. How may it be demonstrated that water, in cooling from 

 4 to 0, increases in volume ? 



18. In a determination of the composition of water by the 

 method of Experiment 137, the following observations were made : 



Wt. of bulb and oxide before heating . . . . 40'63 g. 



Wt. of bulb and copper after heating . . .. 35*78 g. 



Wt. of small bulb and drying- tube before expt. , . 65 '34 g. 

 Wt. of small bulb and drying-tube after expt. . . 70*81 g. 

 Find the weight of oxygen combined with 2 g. of hydrogen. 



19. Why should the combustion tube and the copper oxide 

 used in Experiment 137 be carefully dried before weighing ? 



20. What volume of steam will be formed by the burning of 

 a cubic foot of hydrogen ? What volume of oxygen will be removed 

 from the air as a result of this combustion ? 



CHAPTER XVIII 



CHEMICAL CLASSIFICATION 



209. The division of substances into the two 

 groups known as elements and compounds has been 

 already dealt with. In this chapter some further 

 subdivisions of these two main classes will receive 

 consideration. 



