80 MASS. EXPERIMENT STATION BULLETIN 165. 



Sulfuric Acid removed. 

 In determining the sulfates the small aliquot which had to be taken 

 owing to the amount of suKates present made a shght error in weighing 

 assume large proportions when figured to sulfates removed from 100 grams 

 of soil. This was especially true of the 2Y2 normal and 5 normal extracts. 

 In almost every case, however, more sulfates were found in the extracts 

 than were present in the original solutions used. Where this was not the 

 case the difference between the amount present in the original solution 

 and the amount found in the extract was so small as to come easily within 

 the limit of error. The results indicated that there was no accumulation 

 of sulfuric acid in the soil which would cause it to become acid. 



Htdrochloric Acid removed. 

 In trying to determine the amounts of hydrochloric acid in the extract 

 by titration it was found that the ammonium sulfate prevented the de- 

 velopment of the color. In making gravimetric determinations no pre- 

 cipitate or cloudiness was observed using 100 cubic centimeter aUquots. 

 This shows that the chlorides if present at all were present in concentra- 

 tions of less than one part per milhon of extract, or less than one-tenth of 

 a milligram removed from 100 grams of soil. 



Nitric Acid removed. 

 Nitric acid could not be determined with any degree of accuracy by 

 the colorimetric method. The few determinations made on the more 

 dilute extracts incUcated that there was no appreciable difference in amount 

 removed between the different plots. The average amount found was 

 1.5 parts per hundred thousand. 



Iron and Aluminium removed. 



The iron determinations could be made colorimetricallj^ only after the 

 largest part of the ammonimn sulfate had been removed, as it prevented 

 the development of the color with the thiocyanate. No colorimetric de- 

 terminations were made on the 23^ normal and 5 normal extracts, as the 

 amount of ammonium sulfate was too large to be driven off by ignition 

 without some mechanical loss. 



In the 2Y2 normal and 5 normal concentrations of ammonium-sulfate 

 extracts, iron and aluminium were determined together by precipitating 

 with ammonia as the hydrate. The precipitates were all light in color, 

 showing that they were mostly aluminimn, but all had some iron present. 



No iron was found in the extracts from the hmed ends of the plots ^\^th 

 any of the ammonium-sulfate solutions, except on plot 6 with the 23^2 noi- 

 mal solution, and on all the plots with the 5 normal solution. In all the 

 extracts from the unlim.ed ends of the plots iron was found in varying 

 amounts. A slight increase in the amount removed, ^^^th an increase in 



