12 The Philippine Journal of Science leia 



N, the standard calcium sulphate solution as prepared above 

 will be about 0.02 N, that is, 1 cubic centimeter will be equiv- 

 alent to about 1 milligram of calcium carbonate. 



The potassium palmitate tablets, as prepared above, will each 

 be found equivalent to 1.5 to 2.0 milligrams of calcium carbonate. 



These pellets should be standardized every week, as they lose 

 strength fairly rapidly. What this loss of strength is due to 

 is not yet certain, but from the data at hand it seems at least 

 possible that it may arise from an acid fermentation of the 

 glucose, bringing about a decomposition of the potassium pal- 

 mitate with the separation of palmitic acid. 



For use in the determination of total hardness, 1 cubic centi- 

 meter graduation mai'ks were etched on a 100 cubic centimeter 

 cylinder, so that volumes up to 105 cubic centimeters could be 

 read. For a determination, 100 cubic centimeters of the water, 

 measured in this cylinder, are transferred to a dry 250 cubic 

 centimeter bottle (the glass-stoppered variety is convenient) . 

 A very small piece of methyl orange paper is suspended in the 

 liquid by means of a platinum wire, while normal sulphuric 

 acid is added from" a dropping bottle until the paper becomes 

 red. The paper is then removed to avoid coloring the liquid. 



The liquid is then aspirated for five minutes with a con- 

 tinuous pressure bulb operated by hand. After aspiration, 1 

 cubic centimeter of phenolphthalein is added, followed by 0.2 

 N alcoholic caustic potash from a pipette, till a faint pink color- 

 ation develops. The liquid is now returned to the cylinder, 

 the bottle being drained as completely as possible. The volume 

 of the liquid is noted within 0.5 cubic centimeter. This will 

 usually be between 102 and 105 cubic centimeters. 



About 10 cubic centimeters of the liquid are then introduced 

 into the mortar. One or more potassium palmitate pellets are 

 then added, until an excess is present, that is, when a pronounced 

 phenolphthalein coloration is produced. More water is then 

 added from the cylinder, until the phenolphthalein coloration 

 completely disappears. The volume of water used is noted. 

 Several more pellets are then added, followed by water, till a 

 second end point is reached. The two determinations should 

 check each other within 0.5 to 1 cubic centimeter. 



It is well to use four or five pellets in the two titrations to 

 avoid any considerable error due to the lack of uniformity in 

 the pellets. 



To calculate the total hardness, it is first necessary to reduce 

 the number of cubic centimeters of the water as used in the 

 determination to the equivalent number of cubic centimeters of 



