EXPERIMENT STATION RECORD. 



Vol. XXV. Abstract Number. No. 6. 



RECENT WORK IN AGRICULTURAL SCIENCE. 



AGRICULTURAL CHEMISTRY— AGROTECHNY. 



A centrifugal method for the deterraination of humus, A. A. Wells, W. H. 

 Stevenson, and W. F. Cooveb {foica Sta. BuL 12.',, pp. 370-3SJ,, figs. -J).— Since 

 the official uietliod, as modified by Frear, i-equires a long time for filtration, 

 and the Mooers-Hampton modification presents some difficulty in the way of 

 preventing losses of hnnuis when the clay is filtered off in a flocculated state 

 and in addition requires a very long time for evaporating the extracts, the 

 authors sought to obtain a new procedure by modification or otherwise. In no 

 case was a satisfactory result obtained by the filtration method. 



The authors devised a centrifugal method which utilizes a Gallenkamp cen- 

 trifuge, containing in its drum a platinum cup for holding the soil. The method 

 is as follows : 



"After washing free from chlorids, the soil is transferred to a 1-liter shaking 

 I)ottle with 500 cc. of a 4 per cent ammonia solution, using a glass rod to loosen 

 the soil. . . . The ilask is then stoppered with a rubber stopper, placed in the 

 shaking apparatus, [which is described], and shaken at the rate of 50 revolu- 

 tions per minute for 3 hours. At the end of this time the bottles are removed 

 and the contents allowed to settle for 10 minutes. . . . About 350 cc. of the 

 solution is then decanted through a funnel into the centrifuge bowl, the top 

 clamped in place, and the solution whirled for 10 minutes. By means of a 

 thumb screw a part of the solution is drawn off through the glass tube while 

 the machine is still at full speed. The first 10 cc. is discarded and then about 

 70 cc. of the solution is collected. This amount is readily caught in a small 

 beaker, which should be covered at once with a cover glass to prevent loss by 

 evaporation. 



" Fifty cc. of the solution, which represents 1 gm. of soil, is drawn off with a 

 pipette, placed in a weighed porcelain dish, and evaporated to dryness on a 

 steam bath. The dish is then dried to constant weight in an oven at 110° C, 

 and the weight recorded. The contents of the dish are then ignited in a muffle 

 furnace and weighed again after cooling to room temperature. The loss in 

 weight upon ignition represents the weight of the humus, and the increase of 

 the last weighing over the empty dish represents the weight of the ash." 



With this method the time required for determining the humus is reduced to 

 one-third of that usually employed for the official method. 



Studies on the detection of adulteration in bone superphosphate, G. Masoni 

 (Sta::. Sper. Agr. Ital., j^S {1910), No. //, pp. 297-328; abs. in Chem. Zenthl., 

 1910, II, No. 8, PI). 595, 596; Chem. Ahs., 5 {1911), No. 8, p. i//S//).— Methods for 



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