On the Metallic Salts. 45 



genions arguments to prove that position ; but in this, however, 

 he appears to me to have failed. 



Admitting the correctness of his experiments, wliich, having 

 tried them myself, I do expHcitlv, still I am inclined to consider 

 that he has drawn wrong conclusions from the data before him, 

 and tiiat his reasoning tliereon is fallacious and in some measure 

 contradictory. He says that any dry metallic salt, moistened 

 with water, and indicating acidity by the test, cannot in the dry 

 state be considered neutral, it must in the dry state be an acid 

 salt with excess of oxide caused by the evaporation of part of the 

 acid in the process of drying and depositing its oxide upon solu- 

 tion: — Can the existence of a salt be imagined with each of its 

 constituent parts in excess (i. n. acid and oxide) ? Certainly not. 



I cannot conceive any period during the formation of a salt, 

 that the action towards chemical union would cease, whilst n 

 portion of both jts constituents remain in contact and imcom- 

 bined ; thougii it is easy to conceive that either one of the com- 

 ponent parts may preponderate as in the super and sub salts. It 

 is impo-sil)le to tiy tiic experiment in a direct way, the salt be- 

 ing in a dry state or combined only with the water of crystalliza- 

 tion; when, theiefore, we cannot refer to direct experiment, we 

 must be contented in drawing conclusions from analogy. 



Metallic salts are generally, if not Uiiiversaliy, more soluble 

 according to the greater proportion of free acid, and it is abso- 

 lutely necessary to have a little excess to induce solution : this 

 is not only the case with metallic, but also obtains with many 

 of the earthy salts, such as the sulphates, phosphates, &c. And 

 were his argumenfr allowed, that the salt was not neutral, because 

 it required excess of acid for its solution, these also would be con- 

 sidered super salts: now, it is not doubted that sulphate of lime 

 is not neutral, because it is scarcely soluble without excess of 

 acid. But, he says, before the free acid can be neutralized by 

 an alkali, the oxide is precipitated : this is indeed the fact, anil 

 did it not take place there would l)e no solution : it only proves, 

 therefore, that its tendency towards solution decomposes part of 

 the salt to support the remaining part in the water. 



Besides, the very evidence botli of acid and oxide upon solu- 

 tion clearly proves that tliey w-erc actually combined, and formed 

 part of the salt when crystallized, and not caused by the evapo- 

 ration of part of the acid in drying : were this the case, there 

 would then only lie a superabundance of oxide, and consequently, 

 rather a sub than a super salt. 



I am decidedly of opinion ; First, from the acid or super-salt* 

 being more soluble than the neutral or than the sub-salts; Se- 

 condly, from the salt dissolving without any precipitation on tha 

 affusion of acidulated water ; and 'J'hirdly, iioia the dccompo'si- 



tJDU 



