TWO FIELD METHODS FOR THE DETERMINATION OF THE 

 TOTAL HARDNESS OF WATER ^ 



By A. S. Behrman 



(From the Laboratory of General, Inorganic, and Physical Chemistry, 

 Bureau of Science, Manila) 



In a field examination of the chemical quality of water the 

 determination of total hardness is one of the most important 

 analytical procedures. The data thus obtained, when used in 

 conjunction with the results of the other commonly made deter- 

 minations, give definite and quantitative information as to the 

 nature of the most important of the dissolved constituents. 

 This knowledge may be employed to advantage in connection 

 with various problems related to water supplies, such as pota- 

 bility, purification, and industrial applications. 



The Blacher method ^ for the determination of the total hard- 

 ness of water by titration with potassium palmitate has been 

 found to possess several marked advantages over the standard 

 soap solution and similar procedures. It is clear-cut, accurate, 

 and rapid. 



Based on a study ^ of this method as applied to the analysis 

 of typical Philippine waters, two field methods for the deter- 

 mination of hardness have been devised. Both are "tabloid" in 

 nature, employing pellets of potassium palmitate instead of a 

 solution of the reagent. 



METHOD I 



The first of these procedures is similar to Leighton's field 

 modification * of the soap-solution method, in that the reagent 

 is added in tablets of three strengths, until a sufficient excess 

 is present to give a characteristic end reaction. Pellets of the 

 same reacting values as those suggested by Leighton for sodium 

 oleate are used, namely, 2.0, 1.0, and 0.5 milligrams of calcium 

 carbonate, respectively. 



One hundred cubic centimeters of the sample are measured 

 into a 250 cubic centimeter bottle. A small piece of methyl 



^ Received for publication September 11, 1917. 



" Blacher, C, Griinberg, P., and Kissa, M., Chem. Zeitg. (1913), 37, 56-8. 

 'Behrman, A. S., This Journal, Sec. A (1916), 11, 291. 

 * Leighton, M. 0., U. S. Geol. Surv., Water Supply Paper (1905), No. 151. 



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