138 JUNIOR GRADE SCIENCE 



found, however, that they could be split up into simpler constituents. 

 From soda he obtained the metal sodium, and oxygen and hydrogen, 

 and from that time, of course, soda could not be regarded as an element. 

 Similarly, if in the future it should be found that any of the forms 

 of matter which we call elements can be split up into simpler bodies 

 with different properties, the element which is thus decomposed will 

 have to be struck off the list. Of the elements known to chemists 

 some exist in the gaseous state under ordinary conditions of tempera- 

 ture and pressure. The commonest of these are hydrogen, nitrogen, 

 oxygen and argon. Two elements, bromine and mercury, are liquids. 

 The rest are solids, and some of the commonest are given in the table, 

 the metals being printed in small capitals. 



SOME OF THE COMMONEST ELEMENTS. 



Oases Solids 



Hydrogen ALUMINIUM MAGNESIUM 



Nitrogen ANTIMONY Phosphorus 



Oxygen BARIUM POTASSIUM 



Argon CALCIUM SILVER 



Carbon SODIUM 



Liquids COPPER Sulphur 



Bromine GOLD TIN 



MERCURY IRON ZINC 



LEAD 



63. COMPOUNDS. 



i. Mixture and compound. Take about one gram of powdered sulphur 

 and mix thoroughly with the same quantity of iron filings. Divide the 

 mixture into two portions. Place one portion in a crucible covered with a 

 lid and heat till all the sulphur appears to be burned off. Now examine 

 both portions, (a) Appearance. (6) Try with a maguet. (c) Test the 

 solubility in carbon disulphide. (d) Action of hydrochloric acid. 



What is a complex substance ? A definition for a simple substance 

 has been arrived at, but when it is attempted to state clearly what is 

 meant by a complex substance difficulties arise, owing to the fact that 

 the same two elements maygive substances differing widely in properties. 

 It is evident, for example, that mercury oxide is not a mixture of mercury 

 and oxygen, although it is known to contain both. Again, if equal 

 weights of iron filings and sulphur are mixed as thoroughly as possible 

 the resulting mixture has the properties which would have been antici- 

 pated. In colour it looks not so dark as iron and not so light as sulphur. 

 It is possible to remove the iron from the mixture by means of a magnet, 

 or the sulphur may be removed by solution in carbon disulphide, leaving: 



