SPECIFIC GRAVITY OF METALS. 



389 



The affinity of metals for oxygen is in an inverse ratio to their specific 

 gravity, as can be ascertained by experiment, when the heaviest metal will 

 be the least ready to oxidise. Metals differ in other respects, and thus 

 classification and division become easier. The fusibility of metals is of a 

 very wide range, rising from a temperature below zero to the highest heat 

 obtainable in the blow-pipe, and even then in the case of osmium there is 

 a difficulty. While there can be no question that certain elements, iron, 

 copper, gold, silver, etc., are metals proper, there are many which border upon 

 the line of demarcation very closely, and as in the case of arsenic even 

 occupy the debatable land. 



SPECIFIC GRAVITY is the relation which the weight of substance bears 

 to the weight of an equal volume of water, as already pointed out in PHYSICS. 

 The specific gravities of the metals vary very much, as will be seen from the 

 table following water being, as usual, taken as I : 



Aluminium 

 Antimony 

 Arsenic . 

 Bismuth . 

 Cadmium 

 Calcium . 

 Chromium 

 Cobalt . 

 Copper . 

 Cold 

 Indium . 

 Indium . 

 [ron 



11-4 

 10-5 



972 



2'5 

 1 1-8 



7-2 



5*3 



17-6 



18*4 



7-1 



4'3 



Some metals are therefore lighter and some heavier than water. 

 The table underneath, gives the approximate fusing points of some of 

 the metals (Centigrade Scale) 



Platinum* 

 Gold . 

 Silver . 

 Cast iron 

 Wrought iron 

 Copper . 

 Antimony 



(Ice melts at o.) 



about 1500" 



1200 



iooo r> 

 1000-1200 



1500 



1100 



432 



Zinc 



Lead . 

 Bismuth . 

 Tin 



Sodium . 

 Potassium 

 Mercury 



about 400 

 330 

 ,, 265 

 235 



,, 97 

 60 



40 



There are some metals which, instead of fusing, that is, pasing from the 

 solid to the liquid state, go away in vapour. These are volatile metals. 

 Mercury, potassium, and sodium, can be thus distilled. Some do not expand 

 with heat, but contract (like ice), antimony and bismuth, for instance, while 

 air pressure has a considerable effect upon the fusing point. Some vaporise 

 at once without liquefying ; others, such as iron, become soft before melting. 



Requires oxy-hydrogen blow-pipe. 



