ELECTIVE ATTRACTION. 



solution. The magnesia is of course dis- 

 engaged : and half a bracket, with the 

 point downward, is placed over it, to de- 

 note, that it falls to the bottom, or is pre- 

 cipitated. 



III. The above instances exhibit simple 

 elective attractions : but this method is 

 more particularly applicable to the com- 

 pound attractions. For example : Sup- 

 pose a solution of the muriat of potash 

 be added to sulphat of lime, no de- 

 composition will take place. This is ex- 

 pressed as under : 



{Potash Sulphuric"* 

 acid i Sulphat 

 Muriatic foflime. 



acid Lime J 



The want of horizontal brackets in this 

 scheme denotes, that the principles pre- 

 sented to each other do not unite, and, 

 consequently, that no decomposition en- 

 sues. 



IV. On the contrary, if sulphat of pot- 

 ash be presented to the muriat of lime, a 

 mutual decomposition will ensue. Thus, 



Muriat of potash 



Sulphat 

 of pot- < 

 ash 



Totush 



Muriatic' 

 acid 



Muriat 

 > of lime 



Sulphuric 

 acid Lime 



> 



~ y^ 



Sulphat of lime 



In this scheme we see, that the prin- 

 ciples presented to each other do unite, 

 as is shown by the horizontal brackets, 

 and form the new compounds, muriat of 

 potash and sulphat of lime ; the former 

 of which remains in solution, as is shown 

 by its bracket being turned upward ; 

 while the latter, being nearly insoluble, 

 falls down, and is accordingly denoted 

 by a bracket, the point of which is turned 

 downward. 



V. By attentively observing this last 

 scheme, it may be seen, that the attrac- 

 tions exerted between the simple sub- 

 stances, which are placed over each other, 

 are the quiescent affinities, and tend 

 to preserve the original combinations ; 

 whertas the attractions between the sim- 

 ple substances which stand opposite to 

 each other are the divellent affinities, 

 and tend to produce ne,w combinations. 



If we could determine numerically the 

 simple attractions, it is evident, tbat we 

 might foretel every result which might 

 be produced by the application of com- 

 pound substances to each other, under 

 like substances; as may be shown by ap- 

 plying Morveau's numbers to the preced- 

 ing scheme. 



Muriat of potash 



ash 



Muriat 

 of liint: 



ri j otash o Muriatic" 

 * Z acid 



+ - 



I 54 



I Sulphuric &6 

 V_ acid Lime 



v __ _ _ / 



^^v 

 Sulphat of lime 



The attraction between the potash and 

 sulphuric acid is expressed by the num- 

 ber 62 : and the attraction between the 

 muriatic acid and lime is expressed by the 

 number 23. These are the quiescent af- 

 finities, and their sum 85 expresses the 

 tendency to preserve the original forms 

 of sulphat of potash and muriat of lime. 

 On the other hand, the attraction between 

 the potash and muriatic acid is expressed 

 by 32, and the attraction between sul- 

 phuric acid and lime by 54. The sum of 

 32 and 54 amounts to 86, and expresses 

 the divellent affinities, which tend to pro- 

 duce new combinations. And as this hist 

 sum exceeds the sum of the quiescent at- 

 finities, it follows, that the double decom- 

 position will take place. 



VI. These examples have designedly 

 been taken the reverse of each other ; 

 but every instance, singly exhibited, dors 

 in fact point out both the affirmative and 

 the negative propositions. Thus, from 

 the facts first exhibited, that magnesia 

 does not decompose the combination of 

 potash and sulphuric acid, it likewise fol- 

 lows, that potash does compose the com- 

 bination of sulphuric acid and magnesia. 

 And accordingly, in the last two schemes 

 of double affinity, it is clearly ascertained, 

 from the mutual decomposition of sulphat 

 of potash and muriat of lime, that the mu- 

 riat of potash and sulphat of lime will not 

 decompose each other. 



The same horizontal bracket, which, in 

 the humid way, was used to denote solu- 

 tion, is used to denote sublimation in ex- 

 periments in the dry way. 



The following schemes from Bergman 

 will require no explanation, after the in- 

 stances we have exhibited. 



