§ 98. THE CHEMICAL ANALYSIS. 173 



tube, and the flow of the water through the apparatus is 

 continued until it comes away from the last tube tolera- 

 bly clear. The remainder of the operation is conducted 

 in the same manner as when using Nobel's apparatus. 



THE CHEMICAL ANALYSIS. 



98. The soil for tliis analysis should always be taken 

 in its natural, air-dried condition, without previous igni- 

 tion to expel the organic matter, since the ignition may 

 at the same time alter very materially the effect of the 

 agents employed for solution. 



a. Hydroscopic water and other volatile matter.— 



Determine the amount of water expelled at 100° C. from 

 10 grms. of soil (§ 90), and then ignite the dried residue 

 to determine water chemically combined or otherwise re- 

 tained at 100° C, humus, and volatile mineral substances 

 (§ 91) ; the ignited residue should be treated with am- 

 monic carbonate, if a qualitative test reveals the presence 

 of carbonic acid in the soil, and carbonic acid should be 

 determined in the ash (§ 91, d). 



A. Miiller allows but little value to this estimation of 

 water of hydrates in the soil, and organic matter, even 

 when combined with the determination of carbonic acid 

 both before and after ignition. 



h. Estimate carbonic acid in 5-10 grms. of soil, dried 

 at 100° (§ 60, h). 



c. Determine the total nitrogen in 5-10 grms of soil, 

 dried at 100°, by combustion with soda-lime (§ 85). 



A. Miiller mixes the soil with about an equal quantity 

 of caustic i^otash or soda, instead of Avith soda-lime, but 

 fills the rest of the tube with soda-lime in the usual man- 

 ner ; in this way he avoids the use of very long combus- 

 tion-tubes. 



If much nitrate is present in the soil, and but little hu- 



