ANALYSIS OF COMPLEX MATTER 149 



8. Collect, measure, and examine separately the gases which are 

 given off at the points where very dilute hydrogen sulphate makes 

 contact with an electric circuit. Use platinum plates for making 

 contact. 



9. Add an acid to calcium carbonate (marble or limestone) and 

 cause some of the gas to pass through a solution made by shaking up 

 with water another portion of the calcium carbonate after it has been 

 strongly heated for some time. Observe that the same result is given, 

 if air from the lungs, or air in which a substance containing carbon has 

 been burnt, be passed through some of the same solution, and also that 

 the calcium carbonate loses the gas under observation, when it is at a 

 high temperature. Prove also that this gas is contained in the atmo- 

 sphere in small quantities. Show that the white precipitate formed 

 contains the same gas, and is therefore calcium carbonate. 



10. Arrange an experiment to show that air will burn in an atmo- 

 sphere of coal-gas. Force the air slowly through a tube by means of 

 water falling into a vessel with which the tube is connected. Have 

 ready a vessel supplied with coal-gas which is burning at a small open- 

 ing. Light the jet of air as it enters at this opening and extinguish the 

 gas. Care is needed. 



11. Perform experiments illustrating the law that chemical com- 

 bination takes place between definite quantities of different kinds of 

 matter. 



12. What physical changes usually accompany chemical changes ? 



13. Suggest some hypothesis as to the manner in which chemical 

 change proceeds and the causes by which it is set up. 



14. What facts lead us to believe that the molecule of hydrogen 

 contains two atoms ? 



15. How are the chemical properties of a body distinguished from its 

 physical properties ? How can it be proved that diamond and charcoal 

 are the same kind of matter ? 



16. How would you proceed to find out whether two gases are alike 

 without making use of chemical methods ? 



17. What are the experimental facts and theoretical considerations 

 from which the numbers called atomic weights or masses are derived 



18. What is a lam of nature 1 



