Loess Soils of the Transition Region 5 



" Ofificial " method. In most cases a slight amount of finely- 

 divided clay is carried through the filter in this method, also, but 

 the amount is so slight that the error caused by it is negligible, 

 being less than the experimental error. As stated above, how- 

 ever, the method is accurate and its results may be relied upon 

 when it has been performed correctly. 



THE RATHER METHOD 



The " Rather " method, however, was found to be more satis- 

 factory than either of the other two, especially where a large 

 number of gravimetric determinations are to be made, since it 

 combines the speed of the " Official " method with the accuracy of 

 the " Hilgard " method. The " Rather " method, as named after 

 the man who proposed it, is a modification of the " Official " 

 method, and was originally described in the Journal of Industrial 

 and Engineering Chemistry'^ as follows : 



" Prepare humus solution as described in the ' Official ' method, 

 and dissolve 0.65 gr. of ammonium carbonate in 130 c.c. of the 

 solution. Allow to stand over night in a glass-stoppered cylinder 

 to allow the clay to settle, and decant the clear supernatant liquid 

 thru a dry filter into a dry flask. Evaporate 100 c.c. of the fil- 

 trate in a tared platinum dish, dry for three hours at 100°, weigh, 

 ignite and weigh again. Record loss on ignition as humus." 

 This method gave results concordant with those of the Hilgard 

 method, and in view of this, together with the fact that it required 

 much less time and attention, it was adopted for all the gravi- 

 metric determinations given below. The success of this method 

 is due to the fact that the finely-divided clay is flocculated by the 

 ammonum carbonate and held by the filter. Because of this floc- 

 culation of clay one might expect a lowering of the percentage 

 of the so-called " humus ash," and this is actually the case, as this 

 method gave a lower percentage of humus ash than did any other. 



THE BLISH METHOD 



Still another method suggested itself during the course of the 

 work, and this may be referred to as the " Blish method." This 



^Jour. hid. and Eng. Clicvi., Vol. 3, 191 1, pp. 660-662. 



115 



