314 A Sketch of the Laws of Chemical Combination. 



with tlie laws of definite proportion, wliich are directly deduced from 

 experiment. 



When the volume of gases is compared with their equivalent weights, it 

 has been shown by Gay Lussac, that there is a very simple ratio between 

 them all. The combining equivalents of hydrogen, nitrogen, chlorine, and 

 cyanogen, for example, are 1, 14'15, 35'42, and 26'39 respectfully j but 

 when these different weights are measured, they are found to occupy 

 exactly the same space; a similar quantity of ammonia or of binoxide of 

 nitrogen possesses double the volume ; and of oxygen, only half. This 

 fact is usually referred to under the title of the Theory of Volumes ; and it 

 has been shown, that the combining volumes of substances in the state of 

 gas or vapour, whether elementary or compound, are either equal, or have 

 the simple ratio of I to 1, 2, 3, &c. It thus appears that the laws of 

 combination may be deduced as well from the volumes as from the weights 

 of the combining substances ; and this may now be regarded as one of the 

 best established laws in Chemistry. 



In investigating the composition of inorganic substances, we always find 

 them made up of binary compounds. Thus sulphuric acid is formed by 

 sulphur and oxygen, and potash by potassium and oxygen. Each of these 

 is a binary combination ; and the two may unite to form a double binary 

 or quaternary compound, sulphate of potash, which is termed a salt. This, 

 although apparently neutral, has electro-positive properties, and will com- 

 bine as a base with a similar combination, viz. sulphate of alumina, form- 

 ing with it a double salt, familiarly known as alum. 



The two great classes of acids and alkalies, formed by the union of 

 oxygen with other elementary bodies, were long considered as the only 

 combinations to which these terms could be applied, and by which salts 

 could be formed ; but later researches in chemistry have shown that sul- 

 phui", chlorine, iodine, bromine, fluorine, the compound body cyanogen, and 

 probably some other substances, are capable of forming combinations 

 which deserve the terms acid and base, and which produce distinct salts by 

 their union. Thus the proto-sulphurets of electro-positive metals, termed 

 sulphur-bases, correspond to the alkaline bases of those metals formed by 

 their union with oxygen j and they combine with the sulphurets of electro- 

 positive substances, or sulphur-acids, which are analogous in composition 

 to the acids which the same substances produce by union with oxygen. 

 Hence if the sulphur of a sulphur-salt be replaced by an equivalent quan- 

 tity of oxygen, an oxysalt is the result. Thus the bisulphuret of carbon, 

 or the sesquisulphuret of arsenic, form a salt with sulphuret of potassium, 

 which, by the substitution of oxygen for sulphur in each ingredient, would 

 form carbonate or arsenite of potash. 



The gradual development of facts of this kind, principally by the re- 

 searches of Berzelius, has caused the extension of the term salt to all the 



