OXYGEN AND ITS SALINE r< >M 111 NAT 1 >.\- 195 



amount, because, as forming the last stage of chemical reaction, they 

 are capable of only a few chemical transformations, the energy of the 

 elements being evolved (passing into heat) both in the formation of 

 oxides and in their mutual combinations ; hence in salts there re- 

 mains but little energy. Organisms are bodies in which a series of 

 uninterrupted, varied, and active chemical transformations proceed, 

 whilst salts, which only enter into double decompositions between 

 each other, are incapable of such changes. But organisms always 

 contain salts. Thus, for instance, bones contain calcium phosphate, 

 the juice of grapes, potassium tartrate (cream of tartar), certain 

 lichens, calcium oxalate, and the shells of mollusca, calcium car- 

 bonate, &c. As regards water and soil, portions of the earth in 

 which the chemical processes are less active, they are full of salts. 

 Thus the waters of the oceans, and all others (Chap. I.), abound in 

 salts, and in the soil, in the rocks of the earth's crust, in the up- 

 heaved lavas, and in the falling meteorites the salts of silicic acid, and 



more electro-positive than hydrogen, whilst they forgot that hydrogen may, under different 

 circumstances, displace zinc for instance, at a red heat. Chlorine and oxygen were con- 

 sidered as being of opposite polarity to hydrogen because they easily combine with it, whilst 

 one and the other are capable of replacing hydrogen, and, what is very characteristic, in 

 the replacement of hydrogen by chlorine in carbon compounds, not only does the 

 chemical character often remain unaltered, but even the external form remains un- 

 changed, as Laurent and Dumas demonstrated. These considerations undermine the 

 binary theory, and especially the electro-chemical system. An explanation of known 

 reactions then began to be sought for not in the difference of the polarity of the 

 different substances, but in the joint influences of all the elements on the properties of 

 the compound formed. This is the reverse of the preceding hypotheses. 



This reversal was not, however, limited to the destruction of the tottering founda- 

 tions of the preceding theory ; it projected a new doctrine, and laid the foundation for 

 the whole contemporary direction of our science. This doctrine may be termed the 

 unitary theory that is, it is such as strictly acknowledges the joint influences of the ele- 

 ments in a compound substance, denies the existence of separate and contrary components 

 in them, regards copper sulphate, for instance, as a strictly definite compound of copper, 

 sulphur, and oxygen ; then seeks for compounds which are analogous in their properties, 

 and, placing them side by side, endeavours to express the influence of each element on 

 the united properties of its compound. In the majority of cases it arrives at systems of 

 consideration similar to those which are obtained by the above-mentioned hypotheses 

 but in certain special cases the conclusions of the unitary theory are in entire opposition 

 to the binary theory and its consequences. Cases of this kind are most often met with 

 in the consideration of compounds of a more complex nature than salts, especially 

 organic compounds containing hydrogen. But it is not in this revolution from an 

 artificial to a natural system, important as it is, that the chief service and strength of 

 the unitary doctrine lies. By a simple review of the vast store of data regarding the 

 reactions of typical substances, it succeeded from its first appearance in establishing a 

 new and important law, it introduced a new conception into science namely, the 

 conception of molecules, with which we shall soon become acquainted. The deduction 

 of the law and of the conception of molecules has been verified by facts in a number of 

 cases, and was the cause of the majority of chemists of our times deserting the binary 

 theory and accepting the unitary theory, which forms the basis of the present work. 

 Laurent and Gerhardt must be looked on as the propagators of this doctrine. 



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