with Observations on the Analysis of Sall-lrines. 93 



pound saline solution, and on what principle can it be determined 

 what are the binary compounds that really exist in it ? — a ques- 

 tion of considerable importance, but one at the same time of 

 very difficult determination. 



When it is admitted that this cannot be inferred with certainty 

 from the actual products of analysis, the next most obvious view 

 is, that it may be inferred from a knowledge of the real forces of 

 affinity, as, according to these, certain binary compounds must 

 be formed ; and, as the state of the science does not afford any 

 certain estimate of the strength of attraction, the problem, it 

 may be concluded, is at present incapable of being £-olved. 



This conclusion, however, is by no means certain. Attraction 

 is so much modified in its operation by external forces, and com- 

 binations are so frequently established from the influence of these, 

 that it is not clear that we should be able to determine what 

 combinations would exist in cases similar to those connected with 

 the present investigation, from a knowledge of the degrees of 

 attraction, were we even in possession of it. It is rather, per- 

 haps, from a knowledge of the influence of these external forces, 

 that an approximation to the solution of the problem is to be 

 attained ; and an extension of the principle 1 have illustrated m 

 the preceding part of this paper, it appears to me may throw 

 some light on the question. 



If the force of cohesion has so much power in modifying che- 

 mical attraction, as to change its results, and establish combina- 

 tions independent of the relative degrees of strength with which 

 it is exerted ; and if the reverse of cohesion, that is, the power 

 of a solvent, operates in establishing the reverse combinations, 

 as, in considering the agencv of alcohol in this analysis, there 

 has appeared sufficient reason to conclude, then it will follow, 

 that as in a concentrated medium the least s*)luble compounds 

 are formed, so in a dilute medium the more soluble compounds 

 will be established. The power of the solvent is exerted with 

 greatest effect on those which are most soluble ; and hence, if 

 the reverse combinations even existed, this power must change 

 them, and establish the others, precisely as the power of cohe- 

 sion acts with most energy on those which are least soluble, and 

 thus causes their formation, when it is brought to act with suffi- 

 cient force. Hence will follow the simple rule by which the 

 state of combination may be determined ; that, in any fluid con- 

 taining the elements of compoimd salts, the binary compounds 

 existing in it will be those which are most soluble in that fluid ; 

 and the reverse combinations will only be established by its con- 

 centration favouring the influence of cohesion. Thus, if we con- 

 centrate a solution containing sulphuric and muriatic acids, soda 

 and lime, we know that, from the influence of cohesion, the 



binary 



