172 



§ 97. ANALYSIS OF SOILS AND KOCKS. 



the fatty acid that is set free by the acetic acid envelopes 

 the fine particles of earth, and the flocculent sediment 

 can be filtered out without difficulty. The fatty acid 

 may then be removed from the other solid matters, with 

 which it is mixed, by ignition, or by treatment with alco- 

 hol, and the residue will represent the finest portion of 

 the soil. 



h. The following method of silt analysis, by Dietrich 

 {Fi'esenius' s Zeitschrift^ 5, 296) is preferred by some to 

 that described above ; the apparatus may be easily con- 

 structed out of the ordinary stock of the laboratory. 



The water is caused to flow, under a constant pressure 

 of 1 metre, through a series of four tubes of different 

 sizes, and inclined to the horizon at diff*erent angles, as 

 follows ; 



Each tube is drawn out at one end so that a rubber 

 tube can be attached to it, while the other end is closed 

 with a rubber cork, through which a short glass tube 

 passes ; each tube is connected with the next larger one 

 by a rubber tube passing from the corked end of the 

 former, which is at the same time the upper end, to the 

 lower, tapering end of the latter, and the water flows 

 from the upper end of one tube to the lower end of the 

 next larger one. Each rubber tube is cut in the middle 

 of its length, and the cut ends are connected together by 

 a short glass tube ; each rubber tube also has a clamp on 

 it, by means of which the flow of the water can be regu- 

 lated. The 30 grms. of soil, prepared as for the silt 

 analysis with Nobel's apparatus, are put in the first 



