22 The Philippme Journal of Science isis 



orange (or butter yellow) paper is suspended in the liquid by 

 a hooked platinum wire, and normal sulphuric acid is added 

 from a dropping bottle, until the indicator gives a decided acid 

 reaction.'^ The paper is then removed from the bottle, to avoid 

 absorption of the indicator. The solution is next strongly as- 

 pirated for five minutes, to remove carbon dioxide, using a 

 continuous pressure atomizer bulb. When the aspiration has 

 been effected, 1 cubic centimeter of phenolphthalein indicator 

 solution (1 per cent) is added to the liquid by means of a 1 

 cubic centimeter bulb pipette. The acidity of the solution is 

 neutralized with 0.2 N alcoholic potash, which is added drop by 

 drop until a barely perceptible pink is observed. 



The solution is now ready for treatment with the pellets of 

 potassium palmitate. These are added in the same manner as 

 in Leighton's method, using first the strong tablets and later 

 the weaker ones, until an excess is present. The end point in 

 this case is a deep phenolphthalein coloration. 



A short cut that may be used advantageously in this method 

 is to pour half of the solution to be treated with the pellets 

 into another receptacle. Strong pellets are added rapidly to 

 the portion in the bottle, until an excess has been provided. 

 The remainder of the liquid is then returned to the bottle, after 

 which the end point may be approached quickly, using the infor- 

 mation gained in the treatment of the first portion." 



METHOD II 



The second procedure differs from the first in that the end 

 point is reached when an excess of the water, instead of potas- 

 sium palmitate, is present. In addition, pellets of only one 

 strength are employed, "whole" tablets being advantageously 

 used. 



A 100 cubic centimeter portion of the sample is acidified, 



° The addition of acid would, of course, be unnecessary in the case of a 

 water with an acidity due to mineral acids. Such waters are extremely 

 rare in the Philippines. 



' From the number and strength of pellets used, the hardness of the water 

 is readily calculated. Thus, if there were required 7 "whole," 3 "half," and 

 2 "quarter" tablets, having reacting values of 2.0, 1.0, and 0.5 milligrams of 

 calcium carbonate, respectively, the total hardness, expressed in terms of 

 parts per million of calcium carbonate, would be derived from the following 

 expression : 



Total hardness^^'^^^ >< ^^' >< ^'^^ + ^^ >< '''^ + ^' >< ^"^^J^ISO 



100 



