Washington — Constitution of Some Salic Silicates. 571 



From a survey of the literature it appears that, while they, are 

 all attacked by hydrochloric acid, yet the tendency noted 

 above is also manifest here. In general those which contain 

 the greater proportions of the (B/Si) integrals are not apt to 

 furnish gelatinous silica, while this is the common product 

 with those which show much or most of (B"A1). 



Kaolinite, monoclinic. 



As has been noted on a previous page, kaolinite is the most 

 usual and most common end product of the alteration of the 

 feldspars, lenads, scapolites, and zeolites. Its relation to them, 

 and the reason for this fact, are readily seen if we write its 

 formula as follows, assuming the presence of an (R/ 2 A1) inte- 

 gral, B/ here being hydrogen : 



(H 2 Al)AlSi 2 8 + H 2 0. 



This is simply a transformation of the usual formula, H 4 Al 2 Si 2 9 . 

 On this basis kaolinite is to be considered as a hydrated acid 

 aluminum salt of fellenadic acid, the univalent and bivalent 

 metals having been carried off in solution. In the process of 

 alteration the integrals (B'Si) would furnish the quartz gen- 

 erally found along with kaolin, while hydrogen replaces the 

 metal atoms. The persistence of the (B." 2 AI) integral is in 

 harmony with many observations on the weathering of rocks, 

 in which it has been shown that the alumina is the compo- 

 nent which undergoes the least loss, and which has, therefore, 

 been used by Merrill and others as a standard of measurement 

 of the alteration undergone. 



Locust, N. J., March, 1912. 



