Metals. 237 



heat they act upon the metals, and corrode and 

 dissolve them, the acid being loosened by the 

 heat ; as sulphat of potass, common salt, &c. 



The effects of nitre and muriate of ammonia 

 are much more remarkable. When nitre is 

 mixed with the metals, there is a violent de- 

 flagration, attended with intense heat and light, 

 as is the case in mixing it with other combustible 

 bodies, and the metal is oxidized by means of 

 the oxygen contained in the nitre. The alkali 

 of nitre, separated in this manner, proves dif- 

 ferent from the alkali separated by combustible 

 substances, particularly charcoal ; for when they 

 are separated, it is always very mild (because the 

 charcoal supplies it with carbonic acid) ; on the 

 contrary, when deflagrated with metals, it is 

 always very caustic. The alkali of muriate of 

 ammonia also rises caustic in this case. 



Metals do not easily mix with earths, glass, or 

 their own oxides ; but their oxides readily mix 

 with glass, and give it all the different tinges by 

 which it is made to resemble gems, &c. 



Compounds of metals are often more fusible 

 than metals in their separate state ; hence they 

 are generally employed as solders, and the com- 

 pound is of that metal which we desire to unite, 

 mixed with some other, to render it more fusible. 

 Thus the solder of gold is a mixture of gold and 

 silver ; of silver, silver and copper ; of copper, 

 copper and brass, or brass itself. 



I mentioned the variation of specific gravity 



