combined, and during combination have undergone 

 an entire change of properties. A compound in phar- 

 macy is an intimate mixture of substances, but still 

 only a mixture; it is not a chemical compound, the 

 ingredients have not entered into chemical union or 

 combination, 



Chemical Force, like other forces, cannot be de- 

 scribed, for, like them, it is only known by its effects. 

 It is distinguished from other forces by the facts that, 

 First, it produces an entire change of properties 

 in the bodies on which it is exerted, and, 



Second, that it is exerted only between definite 

 weights and volumes of matter. Like the force 

 of cohesion, which is the name given to the attraction 

 which molecules have for each other, and which is 

 great in solids, small in liquids, andapparantly absent 

 in gases, and like the force of adhesion, which is the 

 name given to the attraction which a mass of mol- 

 ecules has for another mass, the chemical force acts 

 only within immeasurable distances: indeed inas- 

 much as the chemical farce appears to reside in 

 atoms, that is to say is exerted inside a molecule 

 while all other forces affect entire molecules, the 

 chemical force may be said to be distinguished; 



Third by being exerted within a smaller distance 

 than that which any other force is exerted. 



Laws Regulating Chemical Combination First. A 

 definite compound always contains the same ele- 

 ments and the same proportions of those elements 

 by weight or volume. 



' Second. When two elements unite in more than 

 one proportion, they do so in simple multiples of 

 that proportion. 



Third. The proportions in which two elements 

 unite with a third are the proportions in which they 

 unite with each other. 



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