Oct. 14, 1918 



Chemistry of Sweet-Clover Silage 



121 



(3) Titrating to the hydrogen-ion concentration, Ph8.3, or the point 

 of color change for phenolphthalein, gave practically the same acidity 

 value as was obtained in the water extract with colorimetric titration. 

 (Compare Tables III and IV, part 2.) 



(4) Titrating to the hydrogen-ion concentration Ph9-3, or the point 

 of color change for thymolphthalein, gave an acidity value about twice 

 that obtained by titrating to the strictly neutral point, Ph7. 



(5) The acidity value of both the water and the alcoholic extracts 

 obtained by titrating to the hydrogen-ion concentration Ph8.3 agreed 

 substantially with the value obtained in the water extract by the colori- 

 metric titration. (See Table III.) 



(6) The hydrogen-ion concentration of the water extract and the al- 

 coholic extract agree substantially for the three points determined. 



Fig. 2. — Graphs showing the quantity, in cubic centimeters, of alkali used in water and alcoholic extracto 

 of silage; obtained by electrometric titration to Ph7. 



(7) These results show that the acidity value in an alcoholic extract of 

 silage obtained by titrating to the color change of phenolphthalein are 

 high in comparison with the true acidity value — that is the hydrogen-ion 

 concentration. The results obtained by the colorimetric titration on 

 the water extract correspond more nearly to the true acidity value than 

 those obtained on the alcoholic extract. It has previously been sug- 

 gested that the higher acidity value of the alcoholic extracts are due to 

 the presence of fatty acids which are soluble in alcohol, but not in water. 

 If this was the case the hydrogen-ion concentration of the water extract 

 should be less than that of the alcoholic extracts. But the data show 

 that this is not so. The higher acidity value obtained in the alcoholic 

 extracts when the colorimetric titration is used is probably due only to 

 the masking of the end point. The alcoholic .extract contains more of 



