160 CHEMISTRY. 



Calcination. 



It is a general fact observed in nature, that metals 

 are always rendered heavier by calcination. 



Dr. Black's Law. 



Dr. Black's law is, that whenever a body changes 

 its state, it either combines with caloric, or separates 

 from caloric. 



Dalton's Rule of Affinity. 



Where two bodies combine in different propor- 

 tions, if the quantity of one of them be assumed as a 

 fixed number, the proportions of the other body that 

 unites to it are in the simplest possible ratio with 

 each other, being produced by multiplying the low- 

 est proportion by a simple integral number, as 2, 3, 

 4, &c. 



Thus, for example, if a metal can combine chemi- 

 cally with different proportions of oxygen ; if 100 of 

 the metal can take nine of oxygen for the lowest de- 

 gree of oxygenation, all the other degrees will be in 

 the proportion of 100 to twice 9 (18) of oxygen; to 

 three times 9 (27) of oxygen; or 100 of metal to . 

 four times 9 (36) of oxygen, and so on. 



Simple bodies are disposed to unite atom to atom. 



Hence, from the relative weights of the consti- 

 tuent parts of a compound, Mr. Dalton infers the 

 relative weights of the ultimate particle or atom of 

 each of the parts ; and this being found, the number 

 of atoms of each constituent which enter into the for- 

 mation of the compound particle is also deduced. 



Unity. 



The substance of which, as far as we know, the 

 smallest relative weight enters into chemical combi- 

 nation, is hydrogen ; on which account the weight of 



