176 



STATE BOARD OF AGRICULTURE. 



Ill order to determine the personal factor in making up the solutions 

 iu the old way, two samples of solution 2 were neutralized according to 

 the otficial method by each of three laboratory assistants working 

 separately. 100 c. c. portions were taken and the dilute ammonia solu- 

 tion run in from a burette encased in a sheet of opaque paper to pre- 

 vent the reading being taken till after the supposed neutral point had 

 been reached. In this way each operation was made absolutely inde- 

 pendent of the others. The conductivities of the solutions were then 

 taken. The readings were found to fall on the curve obtained by the 

 titration at the points to be expected from the quantities of alkali added. 

 The results are reported in Table 2. 



TABLE II. 



From an inspection of their positions on the curve the alkalinity or 

 acidity of the various solutions could be determined. As can be seen 

 from the accompanying figure (Fig. 2, points indicated by °) the amounts 

 of alkali vary considerably, 63.7 c. c. per liter between the extremes, 

 and in no case was an exactly neutral solution obtained. 



CD 



OL. 



5' 



to 



ao 



30 1/.0 



C. C. N Hv-O H. 



F 1 g. X. 



TO 



60 



These examples fairly illustrate the difficulty of making up a suitable 

 reagent by the official method. It is quite possible that in many cases 

 the character of the ''neutral" ammonium citrate solution varies more 

 than in the cases cited and that considerable error may be introduced 

 into determinations in this way. 



