EXPERIMENT STATION BULLETINS. 



415 



sary to proceed with caution in titrating when near the end point and 

 to allow the precipitate to settle in order that the color of the dye 

 could be observed in the clear solutions. The quantity of HCl neutral- 

 ized by the soii bases is determined by difference and its equivalent 

 in bases computed as calcium. For soils containing carbonates it was 

 necessary to use quantities smaller than 20 gms. depending on the 

 amount of carbonates present. 



Method For Determining Excess Acids In Acid Soils. — 10 gms. of air 

 dry soil were placed into each of .several 8 oz. sterelizing bottles, the num- 

 ber depending on the range to be covered to pass tlie neutral point. 0.1 N 

 equivalents of Ca(OH)o were added to the soil portions, in steps in- 

 creasing by 1 cc. in magnitude, with sufficient neutral, distilled water 

 to make the solution total 50 cc. The bottles were then shaken four 

 hours and allowed to stand one day. After standing, the pH of the 

 series was determined, a curve plotted using pH as ordinates and cc. 

 of 0.1 N equivalents as abscissae, and the quantity of Ca(0H)2 required 

 for neutralization determined from the curve to 0.1 cc. of 0.1 N equival- 

 ent. 



These methods were used on 10 and 20 gm. portions of the four soils 

 under experimentation in order to check on different quantities of soil. 

 Kesults for active base determinations are given in Table 1 and those 

 for excess acids are plotted with the second group of curves. It may 

 be seen from these results that good checks were obtained. 



The 20 gm. portions of soil used in the foregoing experiment were 

 washed until the leachings were free from chlorine and the method re- 

 peated on them. These- results are given in Table 1 in the column, HCl 

 neutralized after drying. On the average only about 3.4 per cent more 

 bases were obtained in the heavier soils. Assuming that the more in- 

 soluble soil materials hydrolyze, these results are to be expected. 



Table 1. — Quantities of HCl neutralized by different amounts of soils. Results in cr. 

 0.2 N HCl. 



EFFECT OF VOLUME OF SOLUTION 



It was considered advisable to check pH determinations on different 

 volumes of solution. These results are presented in Table 2, in com- 

 parison with those obtained by the method previously defined. There 



