1 66 



Soil Analysis 



[279, 280 



DETERMINATIONS MADE IN SEPARATE 

 PORTIONS OF THE SOIL 



In addition to the general mineral analysis given above, 

 it is usual to determine nitrogen, nitrates, chlorides^ carbonates, 

 and organic carbon. 



279. Nitrogen. — Weigh out 20 grams of the finely 

 ground sample of soil, and estimate the nitrogen by the acid 

 method (paragraphs 92-95). 



280. Nitrates and Chlorides.— These two con- 

 stituents are estimated in the water extract of soil. The 



apparatus used for the 

 extraction is shown in 

 fig. 44. a is the top of a 

 Winchester quart bottle 

 which has been cut off 

 from the bottom. This 

 is connected, by means 

 of a piece of glass 

 tubing and two well- 

 fitting corks, with the 

 stout tabulated flask b. 



Fig. 44. 



This apparatus is connected first with the safety bottle c, then 

 with the pump d. Inside a is placed a disc of copper gauze 

 2 inches in diameter; this covers the aperture of the neck, and 

 serves as support for a piece of filter paper. By means of this 

 apparatus the whole of the nitrates and chlorides in 500 grams 

 of soil may be extracted with 100 c.c. of water. 



Weigh out 500 grams of the original sample (undried) of 

 the soil, and place it over the filter paper in a (fig. 44). If it 

 be of a loose texture, press it down well ; then pour 50 c.c. of 

 distilled"water over it. After it has stood five minutes, set the 



