20 PRINCIPLES OF CHEMISTRY 



all homogeneous substances maybe classified into simple and compound 

 substances. This view was introduced and established as a scientific 

 fact during the lifetime of Lavoisier. The number of these elements 

 is very small in comparison with the number of compound substances 

 which are formed by them. At the present time, only seventy elements 

 are known with certainty to exist. Some of them are very rarely met 

 with in nature, or are found in very small quantities, whilst others 

 are yet doubtful. The number of elements with whose compounds we 

 commonly deal in everyday life is very small. Elements cannot be 

 transmuted into one another at least up to now not a single ,-ase of 

 such a transformation has been met with ; it may therefore be said 

 that, as yet, it is impossible to transmute one metal into another. And 

 as yet, notwithstanding the number of assays which have been made in 

 this direction, no fact has been discovered which could in any way 

 support the idea of the complexity of those indubitably-known ele- 

 ments 26 such as oxygen, iron, sulphur, &c. Therefore, from its con- 

 ception, an element is not susceptible to reactions of decomposition.- 7 



- fi Many ancient philosophei's admitted the existence of one elementary form of 

 matter. This idea still appears in our times, in the constant efforts \\hicli are made to 

 reduce the number of the elements; to prove, for instance, that bromine contains chlorine 

 or that chlorine contains oxygen. Many methods, founded both on experiment and 

 theory, have been tried to prove the compound nature of the elements. All labour" in 

 this direction has as yet been in vain, and the assurance that elementary matter is not 

 so homogeneous (single) as the mind would desire in its first transport of rapid generali- 

 sation is strengthened from year to year. At all events, there are as yet no experimental 

 or theoretical evidences of the compound nature of our elements. With the methods 

 and evidence now at our disposal it is impossible to even imagine the possibility of a 

 method by which the different elements could be formed from one elementary material. 

 Cases of isomerism and of polymerism of compound substances certainly show the pos- 

 sibility of the formation, from one and the same elements, of substances with different 

 properties, but every change of this kind is completely levelled and nullified by a certain 

 rise in temperature by which every isomeride and polymeride is converted into one 

 variety and changes its original properties All our knowledge Allows that iron and 

 other elements remain, even at such a high temperature as there exists in the sun. as 

 different substances, and are not converted into one common material. Admitting, even 

 mentally, the possibility of one elementary form of matter, a method must lie imagined 

 by which it could give rise to the various elements, as also the )nt><ln* o/it'r<ni(li of their 

 formation from one material. If it be said that this diversitude only takes place at low 

 temperatures, as is observed with isomerides, then there would be reason to expect, if not 

 the transition of the various elements into one particular and more stable form, at least 

 the mutual transformation of some into others. But nothing of the kind has yet been 

 observed, and the alchemist's hope to manufacture (as Berthollet puts it) elements has no 

 foundation of fact or theory. 



27 The weakest point in the idea of elements is the negative character of the determi- 

 native signs given them by Lavoisier, and from that time ruling in chemistry. They do 

 no^decompose, they do not change into one another. But it must be remarked that 

 elements form the limiting horizon of our knowledge of matter, and it is always difficult 

 to determine a positive side on the borderland of what is known. But all the same, if 

 not for all, at all events for the majority, of those having the properties of metals, there 

 is a series of positive common signs (they possess a particular appearance and lustre, 



