ON THE NATURE OF SOLUTION. 93 



Second Report of the Committee, consisting of Professors Tildek 

 and Eamsat and Dr. Nicol (Secretary), afjxjointed for the 

 purpose of investigating the Nature of Solution. 



The mukial solubility of salts which do not act chemicalhj on one another^ 



"While it has been long known that the presence of one salt greatly 

 inflaences the solubility of another salt dissolred in the same mass of 

 water, nothing is known of the laws regulating this phenomenon. Much 

 of our ignorance on this point is doubtless due to the difficulties attending 

 the determination of solubility in general, but more to the fact that 

 experimenters have confined themselves to the task of ascertaining the- 

 effect of one salt on another when both are dissolved simultaneously 

 to saturation. 



An extended series of experiments has been made on the following; 

 lines : — 



Solutions containing definite quantities of one salt have been prepared 

 and a second salt dissolved to saturation in these. Thus solutions contain- 

 ing 2, 4, and 6 molecules of NaCl in IOOH2O were prepared and KOI 

 was dissolved to saturation in these, a special apparatus being employed 

 by means of which complete saturation was ensured without any loss of 

 water by evaporation. Similar converse experiments were made with 

 KCl solutions in which NaCl was dissolved and in all the mutual action 

 of the following pairs was examined : 



1. NaCl in KCl 5. KCl in KNO3 



2. KCl in NaCl 6. KNO3 in KCl 



3. NaCl in NaNO^ 7. NaNO^ in KNO3 



4. NaN03 in NaCl 8. KNO, in NaNO, 



In addition the densities of mixtures of the above salts in various 

 definite proportions up to near the saturation point were determined, and 

 also the mutual solubility to saturation of both members of each pair. 



Time has not permitted us to complete the working out of the data 

 thus obtained, but the general results may be stated as follows : — 



In the first six cases the solubility of the first salt is diminished by 

 the presence of the second when compared with the solubility in pure 

 water. But if each salt is assumed to have its proportionate share of the 

 •water present then the solubility of both salts is increased. 



In pair 7 the solubility of NaNOj is increased by the presence of 

 KNOs, while in pair 8 the presence of a small quantity of NaNOg. 

 diminishes the solubility of KNO3, but a larger quantity increases it. 

 Whether or not this anomalous behaviour is due to the isodimorphism 

 of the two salts, as has been already suggested,' further experiments 

 alone will show ; but it may be here noted that the rhombic form of KNO3 

 is mnch more soluble than the ordinary prismatic form, as is easily 

 proved by allowing a drop of potassium nitrate to evaporate slowly on a 

 glass plate and after rhombic crystals have separated, on touching the drop 

 with a wire, instant crystallisation in the prismatic form results. This also 

 is one of the few instances, if not the only one, of supersaturation in the case 



' Nicol, PJill Marj., June 1884. 



