EXPERIMENT STATION REPORTS. 179 



would be equivalent to 0.00()04:-0.00003 parts of nitrogen per hundred 

 which is quite as accurate as the ordinary distillation methods. The 

 fact that the nitrate nitrogen forms only 3.73% of the weight of 

 the precipitate greatly increases the accuracy of the method over ordi- 

 nary analytical methods. 



NITRATES IN SOIL. 



The following method of ])rocedure was used in the analysis of soils. 

 lOOg. (or a larger quantity if necessarvO were weighed into a beaker 

 and thoroughly stirred with hot distilled water to form a thin paste. 

 After standing sonue time the liquid Avas drawn off with suction and 

 the residue washed on the filter with hot water till the filtrate amounted 

 to 200-300 c. c. The combined filtrate and Avashings were then con- 

 centrated to about 100 e. c, filtered through a folded filter, to remove 

 sediment which may have accumulated during concentration, and the 

 filtrate further concentrated to 50-75 c. c. To this liquid while still 

 hot a few drops of (I-I) HoSO^ were added and then 5-10 c. c. of a 

 solution of "Nitron" in 5% acetic acid. During the addition of precipi- 

 tating reagent the solution was vigorously stirred and the sides of the 

 beaker scratched to insure precipitation. The beaker Avas then set in 

 ice water or in the cold chamber of the refrigerator for several hours 

 or over night. At the end of this time the precipitate Avas transferred 

 to a weighed gooch crucible^ by means of the mother liquor and washed 

 with a few c. c. of ice water applied in a fine jet from a wash bottle. 

 It Avas dried to constant weight at 110°. 



For the distillation method the soil was extracted as above and the 

 ammonia removed from the extract by distillation Avith MgO after 

 which the residue was treated as directed on p. 10 method ''h'' of the 

 official methods. 



EXPERIMENTAL. 



A mixture of 200g. of ]mre quartz sand and 350 mg. of pure KNOo 

 was prepared and extracted as above. The extract was concentrated and 

 made up to 200 c. c. of which aliquots of 25 c. c. Avere taken for analy- 

 sis. 



'"''nitron^^ method. 



25 c. c. samples gave 0.1612 and 0.1G07 g. "Nitron nitrate"=6.01 

 and 5.90 mg. N respectively. 



distillation method. 



25 c. c. samples gave NH,., equivalent io 4.05 and 4.00 c. c. N/10 H. 

 804=5.67 and 5.60 mg. N respectively. 



Theory = 6.06 mg. N. 



The folloAviug are some of the results obtained with samples of soil 

 collected at random from various fields on the college farm. 



The results are not at all concordant. 



^After weighing, the precipitate can be burned off and the same crucible used repeatedly. 



