164 Professors Rogers on the Decomposition 



and of carbonated water, upon mineral compounds. The only 

 results heretofore published on the subject, so far as we are 

 aware, aire the comparatively isolated experiments of Struve, 

 Forchhammer, and Polstorf and Wiegmann, as cited by 

 Liebig, in the last edition of his Agricultural Chemistry.* 

 But these were of too restricted a scope to furnish a solid 

 basis for reasoning generally on the disintegration of rocks, 

 the formation of chalcedonic, zeolitic, and other minerals, by 

 solution, and the conveyance of inorganic materials into the 

 structure of plants. Yet upon such slender experimental 

 foundation rest the common theories of the decomposing and 

 foi'ming action of the meteoric waters. 



It is obviously, therefore, a question of the first importance 

 to decide whether water, pure or charged with carbonic acid, 

 possesses the^en^ra^decomposing and dissolving power which 

 some chemists have, vaguely and without suflficient evidence, 

 ascribed to it, or whether this action is manifested only with 

 the few materials hitherto tried, and which all contain alkali. 



To resolve this question has been the object of our labours; 

 and we feel that we have been well rewarded by the result, 

 proving, as it does most conclusively, the solvent and decom- 

 posing power of pure and carbonated water upon all the im- 

 portant mineral aggregates, as well without as with alkaline in- 

 gredients. 



Our experiments have been of two kinds, first, by an ex- 

 temporaneous method with the tache, and, second, by prolonged 

 digestion at the ordinary temperatui'e. 



In the former method, a small quantity of the mineral, 

 some five or ten grains, in very fine powder, is leached for a 

 few moments on a small filter of purified paper, and a single 

 clear drop of the liquid, received on a platinum slip, is dried 

 and examined by appropriate tests, before and after ignition. 

 In the second process, a quantity (40 grains) of the finely- 

 powdered mineral, is placed with a certain volume (10 cubic 

 inches) of the liquid in a green glass bottle, and agitated 

 from time to time for a prescribed period. The liquid sepa- 



* See also a valuable memoir on the Solubility of Fluoride of Calcium in 

 Water, &c., by G. Wilson, M.D., Trans. Koy. Soc. Edin., xvi., 145, 1846. 



