Aguilar: Waters of Angat and Montalban Rivers 49 

 Table 4. — Results of analyses and computations (station U). 





£E£! 



Keactin^ues. 



««.; 





M,j. p. r 



11.75 





Calcium (Ca) 



£ 



Sulphate (S04) -™~~™~™~"~~~~!~!"~~"~ 







Concentration value 









CoHoids: 









t! 









Groups: 



== 



12.99 















rain 









Properties: 







100.00 



1.1 























100.0 



station 1 and station 5 is due to the preponderance of sulphates, 

 which probably are oxidized decomposition products of iron 

 pyrites. It is well to note, in this connection, that a portion of 

 the watershed of Talaguio River is situated within the district 

 of the Angat iron mines, and its waters are sampled at station 

 1 together with the waters of Maputi and Kailugan. With the 

 exception of the saline waters at Talaguio River, the waters 

 of the various tributaries of Angat River and also those of Mon- 

 talban River are characterized by primary alkalinity, indicating 

 the predominating influence of beds of decomposed igneous and 

 crystalline granitic rocks in their drainage basins. Secondary 

 alkalinity, causing temporary hardness, is also a conspicuous 

 property common to all these waters, acquired no doubt through 

 contact with limestone deposits. 



