86 Remarks on the Theory of Compound Salt Radicals. 



sulphate of potash for an atom of water, the double sulphate of 

 magnesia and potassa (MgO,S0 3 +KO,S0 3 ) + 6Aq, and innume- 

 rable other double salts by a precisely similar replacement, the 

 crystallogenic water remaining constant. Hence it clearly ap- 

 pears that there exists between an oxysalt and an oxide of the 

 magnesian family, an analogy so strong that they are capable of 

 replacing one another in a third substance without altering its 

 molecular type. If then there exists between a double oxysalt 

 and a double chloride that perfect analogy which is asserted by 

 the supporters of the new theory, it follows that one of the two 

 chlorides enters into combination with the other only by replac- 

 ing its water of constitution. Yet a careful comparison of the 

 formulae of the simple and double chlorides clearly shows that 

 such is not the case. Even if it were so, it would only exhibit 

 another argument against the salt-radical theory, since obviously 

 it would then demonstrate that analogy between a simple chlo- 

 ride, as HC1, and a simple oxide, as HO, which is so obstinately 

 denied by the advocates of the new view. 



12. It appears to be a general law in chemistry, that the more 

 simple the chemical constitution of a body, the more simple is 

 its crystalline form. Thus simple substances, with but few ex- 

 ceptions, crystallize in the regular system. Anhydrous proto- 

 halides, as protochlorides, protocyanides, &c. almost universally 

 appear crystallized in cubes or regular octahedrons. Anhydrous 

 protoamphides in like manner, so far as our knowledge of them 

 extends, assume the same forms ; the protosulphides of lead, 

 zinc, and silver, will serve as examples. On the other hand, 

 when the simple molecule of metal assumes more than one atom 

 of amphigen or halogen body, or when the protohalide or proto- 

 amphide combines with crystallogenic or constitutional water, 

 it assumes a more complicated crystalline form and structure. 

 Agreeably to this law the compounds of salt-radicals with metal- 

 lic basyles should, when anhydrous, appear crystallized in the 

 regular system, whereas on the contrary a close examination 

 shows that this is very rarely the case. It appears then that the 

 supposed resemblance between the two classes of salts, viz. the 

 haloid salts and the salts of amphacids and amphibases, fails in a 

 most material and striking manner when they are compared by 

 the only exact standard of physical similarity which we pos- 

 sess — identity of crystalline form. 



New York, October 23d, 1843. 



