86 A TREATISE ON METAMOEPHISM. 



HTBEOLTSIS. a 



Under the theory of dissociation, not only do acids, bases, and salts 

 separate into ions in water solutions, but the water itself is believed to 

 dissociate to a very small extent, according- to the equation H 2 OzrH+OH, 

 thus simultaneously forming free hydrogen and hydroxyl. If this be true 

 the hydrogen ions and the hydroxyl ions coexist and water solutions to a 

 small extent contain free acids and free bases at the same time. The 

 excellence of water as an agent for reactions between the substances it 

 holds in solution is held to be partly due to hydrolysis. 



When strong bases and acids are in solution the amount of their dis- 

 sociation is believed to be so much greater than that of water that the 

 dissociation of the latter is of little consequence. But if a very strong base 

 be united with a weak acid the solution will give an alkaline reaction, and 

 this is regarded as showing the presence of free hydroxyl ions or of 

 hydrolysis. For instance, if the strong base, sodium, be united with the 

 weak acid, carbonic, and a water solution be made, it is held that hydrolysis 

 will take place to some extent, thus: 



Na 2 C0 3 +H 2 0=NaHC0 3 +NaOH. 



It is supposed that NaHC0 3 breaks up into the ions Na and HC0 3 , and 

 the NaOH into the ions Na and OH. Therefore, in a solution of Na 2 C0 3 

 in water the coexistent ions are thought to be H, HC0 3 , Na, and OH. 

 Since the base, NaOH, is stronger than the acid, HC0 3 , the separation into 

 the ions is thought to be the explanation of the alkaline reaction. 



Cameron has shown that sodium silicate in solution gives an alkaline 

 reaction, and his explanation is that this compound is hydrolized in a man- 

 ner precisely similar to that of sodium carbonate.'' Not only do solutions 

 of sodium silicate give alkaline reactions, but Clarke has shown that many 

 natural mineral silicates, when treated with pure water, show an alkaline 

 reaction. The following gave permanent alkaline reactions: Phlogopite, 

 oligoclase, albite, cancrinite, sodalite, analcite, natrolite, pectolite, apophyl- 

 lite, aegirite. The following gave more or less distinct colorations to the 

 phenolphthalein indicator, but in time faded: Muscovite, lepidolite, ortho- 



«Ostwald, W., Grundlinien der anorganischen Chernie, Engelmann, Leipzig, 1900, pp. 254-257. 



6 Cameron, F. K., Application of the theory of solutions to the study of soils: Rept. No. 64, Field 

 Operations of the Division of Soils, 1899, U. S. Dept. of Agric, 1900, p. 169. 



■ c Clarke, F. W., Alkaline reaction of some natural silicates: Jour. Am. Chem. Soc, vol. 20, 1898, 

 pp. 739-742. 



