CENTBAL SCIENTIFIC CO., CHICAGO, U. S. A. 



447 



No. 12252. 



12252. CENTRIFUGES, Moisture Equivalent, Briggs-McLane, as described in the Proceedings of the 



American Society of Agronomy, Volume 2, 1910. 



This centrifuge is used for determining the relative moisture equivalents of soils where the 

 term moisture equivalent designates the maximum percentage of moisture which a soil can 

 retain in opposition to a known centrifugal force. For a standard of comparison, a centrif- 

 ugal force equal to 1,000 times the force oi gravity has been adopted. In making the deter- 

 minations, the soils, suitably moistened, are placed in cups with perforated bottoms. These 

 cups are then placed in the cylinder of the centrifuge and rotated at a constant speed, so 

 chosen as to develop the required centrifugal force. "Each soil now loses water until the 

 capillary forces have increased sufficiently to balance the centrifugal force acting on the 

 soil moisture. Since the moisture content of each soil which has been treated in this way 

 is in capillary equilibrium with the same force, it follows that if these moist soils are placed 

 in contact in any order whatever no movement of water from one soil to another will take 

 place. A condition of complete equilibrium exists throughout the series of soils thus treat- 

 ed." It is then necessary only to determine the moisture content of each soil correspond- 

 ing to this condition of equilibrium in order to determine its quantitative position in the 

 scale of moisture retentiveness. The centrifuge here described is capable of maintaining the 

 required centrifugal force well within the desired limit of accuracy. 



The instrument consists of a bronze disk cylinder containing 16 soil boxes with wire gauze 

 bottoms, and attached to the shaft of a vertically mounted D. C. motor. The motor is pro- 

 vided with a Kellogg Constant Speed Governor and a Frahm Tachometer (not shown in the 

 illustration) is supplied which has a range from 2380 to 2500, thus bringing the desired point 

 of speed, 2440 r. p. m., about the middle of the dial. If alternating current only is avail- 

 able, a motor-generator set should be used to produce the direct current necessary. See 

 Nos. 4824 to 4848. Complete as described. 



Xo A B 



For volts 110 220 



Each $285.60 285.60 



For other CENTRIFUGES, see general heading Centrifuges. 

 COLORIMETERS, see general heading Colorimeters. 



1225fi. COMPACTING MACHINE, designed for obtaining uniform compaction of soils in tubes 18 

 inches or less in length and four inches or less in diameter. It consists of two uprights hav- 

 ing sockets at their lower ends for attachment to the floor and a cross bar with wall attach- 

 ments at their upper ends. A cross bar fastened rigidly to these uprights carries a rotating 

 tube socket or holder which is rotated by means of a crank. Twice during each revolution 

 the tube is raised to the height of *4 inch by means of inclined surfaces under the tube 

 holder, and automatically dropped, which process jars the soil into position. A small propel- 

 ler is attached to the end of the rod extending down from the sliding cross bar. This pro- 



