xiii, A, 1 Heise and Behrman: Water Analysis in Field 



9 



half that with butter yellow — the absence of bicarbonates is 

 indicated. If the alkalinity is found greater than the normal 

 carbonates, the difference will be bicarbonates, all expressed 

 as calcium carbonate. 



If, however, the phenolphthalein titration is more than one 

 half that with butter yellow, the waters contain calcium or 

 other alkaline hydrates (caustic alkalinity). In case the phe- 

 nolphthalein and butter yellow titrations are identical, all of the 

 alkalinity is due to hydrates. 



The relations between the various forms of alkalinity just 

 discussed are shown in Table IV.* 



Table IV. — Relation between normal carbonates, bicarbonates, and hydrates 

 in natural waters, as indicated by titration with sulphuric acid (sodium 

 bisulphate) in cold. 



p=o. 



P<iB 

 P=iB 

 P>iB 

 P=B.. 



Carbon- 

 ates. 



O 

 2P 

 2P 

 2(B-P) 

 O 



Bicar- 

 bonates. 



B 

 B-2P 

 O 

 O 

 O 



Hydrates. 



O . 

 O 



o 



2P-B 

 B 



P, phenolphthalein titration ; B, butter-yellow titration. 



When it is desired to express normal carbonates as sodium 

 carbonate, the calcium carbonate value is multiplied by 1.06. 

 Similarly the bicarbonates may be expressed as HCO3 by multi- 

 plying the calcium carbonate equivalent by 1.22. 



Acidity. — If a water reacts acid to phenolphthalein, the pres- 

 ence of carbonic or a mineral acid is indicated. In the first 

 case bicarbonates may be present, but normal carbonates will 

 not. In the second case neither bicarbonates nor normal car- 

 bonates can be present, and the water will react acid to butter 

 yellow or methyl orange as well as to phenolphthalein. 



Mineral acidity, when present, is determined with pellets of 

 sodium carbonate, using butter yellow as an indicator. Total 

 acidity, due to the combined effect of mineral and carbonic 

 acids, is also determined with pellets of sodium carbonate, but 

 in the presence of phenolphthalein as indicator. The carbonic 

 acid acidity is the .difference between the total and the mineral 

 acidities. 



Mineral acidity in natural waters is rarely encountered in the 

 Philippines. Acidity is practically always due to free carbon di- 



* Cf. Standard Methods of Water Analysis, American Public Health 

 Association, Boston. 2d ed. (1915), .39. 



