294 Miss E. M. Walton on Liquefaction and Cold 



of such substances are not easily separated with a limited 

 supply of water, especially at a reduced temperature. 



Liquefaction without Chemical Reaction. — The second class 

 referred to above includes mixtures of salts of the same base, 

 or having the same acid ; and although it seems to be the ex- 

 ception rather than the rule that there should be liquefaction 

 in such cases, yet this sometimes occurs. 

 Ex. 



-Fe 2 Cl 6 .6H 2 



withFe 2 (N0 3 ) 6 .18H 2 0, 



liquefied 



Fe 2 Cl 6 .12H 2 



.'? ?? 



» 



FeCl 2 .4H 2 0* 



)? J5 



? ? 



FeS0 4 .7H 2 



?J ).' 



?? 



?? 



„ Fe 2 Cl 6 .6H 2 



?j 



Na 2 C 2 H 2 2 .6H 2 



„ PbC 2 H 2 2 .3H 2 



?? 



TJ 



,, K 2 2 H 2 2 



V 



}) 



„ ZnC 2 H 2 2 .3H 2 



V 



Na 2 SO 4 .10H 2 O 



„ ZnS0 4 .7H 2 



?J 



?? 



„ Li 2 SG 4 .H 2 



» 



CaCl 2 .6H 2 



„ Fe 2 Cl 6 .12H 2 



V 



„ CuCl 2 .2H 2 



Some interesting experiments with caustic soda (NaOH) 

 showed that when it was used with any hydrated sodium salt 

 the combined water was liberated, evidently to satisfy the 

 affinity of NaOH for water. 



KOH was also used with various hydrated salts; and in 

 every instance liquefaction ensued. Apparently the hydrated 

 salt was attacked for the sake of its water; and the first reac- 

 tion seems to be appropriation of water by KOH, which is 

 doubtless followed by metathesis in most cases. 



Liquefaction in the examples given above, however, can- 

 not be explained in this way. Neither is there metathesis; 

 and evidently double salts are not formed. 



Having mixed equivalent weights of ZnS0 4 . 7H 2 and 

 Na 2 S0 4 . 10H 2 O, the composition of the resulting solid part 

 was found not to be that of a double sulphate, there being an 

 excess of Na 2 S0 4 . 



Equivalent weights of CaCl 2 . 6H 2 and Ca(N0 3 ) 2 . 4H 2 

 were mixed, also of Fe 2 Cl 6 . 12H 2 and Fe 2 (N0 3 ) 6 . 18H 2 0, 

 with a view to analysis; but in each case the thin liquid dis- 

 appeared entirely into the plaster plate used for absorption, 

 leaving only a stain visible. 



Theory. — These examples must be similar in nature to mix- 

 tures of salts with ice, which result in liquefaction and solu- 

 tion of the salts. 



* Of course a ferric and a ferrous base are not strictly the same ; but 

 ferrous nitrate is too unstable a body with which to work except in the 

 coldest weather. 



