226 Chemistry. [Lecture 32. 



come fluid, like other bodies, in different degrees 

 of it. Many are also volatile when exposed to 

 an intense heat. There is one phenomenon of 

 melted metals, which, to prevent mistake, I will 

 mention; the violent explosion they produce 

 when they touch any thing moist. From what 

 has been previously stated, it is obvious that this 

 effect depends on the great degree of heat the 

 metal is capable of receiving, which converts the 

 moisture into vapour; yet when poured into 

 moulds of sand there is no explosion, though 

 humid, because the vapour easily finds a way 

 through the pores. In general, however, the 

 workmen pierce a number of holes through the 

 sand. Copper and brass produce this effect 

 most, because they receive the greatest quantity 

 of heat when exposed to any given degree. Thus 

 if we expose equal bulks of copper, iron, lead, 

 tin, and silver to the heat of boiling water, and 

 throw them into eqwal quantities of cold water, 

 the copper will heat the water most, the iron 

 next, and so on in the order recited. 



When metals are heated to a very high degree, 

 and the heat continued in the open air, they will 

 be reduced to a calcr, or cinder-like appearance. 

 This is occasioned by their attracting the oxygen 

 from the atmosphere, which then uniting with 

 them, forms them into oxides ; and in this state 

 they are soluble in some degree in water. Gold, 

 silver, and platinum are exceptions to this, for 

 their attraction for oxygen is so weak, that they 



