A NEW HYDROMETER

A CONTINOUS-RECORDING HYDROMETER HADS BEEN DEVELOPED THAT OFFERS THE ACCURACY OF THE PIPETTE METHOD AND THE SIMPLICITY OF THE CASA GRANDE HYDROMETER. A DRAWBACK OF THE CASAGRANDE DEVICE IS THAT THE HYDROMETER HAS TO BE REMOVED FROM THE SUSPENSION BETWEEN READINGS TO PREVENT DEPOSITION OF SOIL PARTICLES ON THE UPPER SURFACE OF THE BULB, WHICH WOULD INCREASE THE WEIGHT OF THE HYDROMETER AND THE DEPTH OF SUBMERGENCE. HOWEVER, THIS REMOVAL FOR READING DISTRUBS SEDIMENTATION. IN ADDITION, ON THE ASSUMPTION THAT A LINEAR REALTIONSHIP EXISTS BETWEEN DENSITY AND DEPTH IN A SUSPENSION, THE CENTER OF BULB VOLUME IS MADE TO COINCIDE WITH THE PLANE OF AVERAGE SUSPENSION DENSITY. HOWEVER, THE RELATIONSHIP IS ACTUALLY LOGARITHMIC, THE PIPETTE METHOD IS ACCURATE, BUT SLOW AND TEDIOUS, AND THERE IS STILL THE POSSIBILITY OF DISTRUBANCE. THE NEW HYDROMETER CONSISTS OF A GLASS TUBE SUSPENDED FROM A FLEXIBLE STEEL CANTILEVER THAT IS SUPPORTED AT ITS FREE END ON A MICROMETER SCREW. THE TUBE IS SUSPENDED AT A POINT ONE-THIRD OF THE CANTILEVER'S LENGTH INTO A GLASS CYLINDER CONTAINING A SOIL SUSPENSION. THE MICROMETER CAN BE USED TO CHANGE THE VERTICAL POSITION OF THE TUBE. TWO ELECTRICAL CONTACTS, ONE FIXED AND THE OTHER ON THE BOTTOM OF THE CANTILEVER, MAINTAIN THE TUBE IN A FIXED POSITION BY OPENING OR CLOSING AN ELECTRICAL CIRCUIT CONNECTED TO A SMALL LIGHT AS THE TUBE PASSES THROUGH THE POSITION. AT THE BEGINNING OF THE SEDIMENTATION THE SUSPENSION IS COMPLETELY DISPERSED AND UNIFORM. AS SEDIMENTATION PROCEEDS WITH TIME, THE DENSITY OF THE UPPER PART OF THE SUSPENSION IN WHICH THE TUBE IS IMMERSED DECREASES OWING TO THE SETTLING OF SOIL PARTICLES. THE RESULTING DECREASE IN BUOYANCY INCREASES THE EFFECTIVE WEIGHT OF THE TUBE, WHICH IN TURN BENDS THE CANTILEVER AND ALLOWS THE TUBE TO DESCEND. THE MICROMETER SCREW IS USED TO RESTORE THE TUBE TO ITS ORIGINAL POSITION. THEREFORE, THE DEFLECTION OF THE FREE END CAN BE RECORDED. BY RECORDING THE CHANGE IN MICROMETER READING AND THE RELATED TIME, A CURVE OF ACCUMUALTED DEFLECTION AGAINST TIME MAY BE PLOTTED. THE NEW DEVICE IS SENSITIVE ENOUGH TO RECORD THE SMALL CHANGES IN DENSITY. THE CHANGE IN DEFLECTION OF THE FREE END OF THE CANTILEVER, DELTA, IS LINEARLY RELATED TO THE EFFECTIVE WEIGHT OF THE GLASS TUBE, M, BY THE EQUATION DELTA = KM, WHERE K IS A CONSTANT EQUAL TO THE SLOPE OF THE CURVE GENERATED BY PLACING KNOWN WEIGHTS ON THE CANTILEVER AT THE POSITION WHERE THE GLASS TUBE IS PLACED AND DETERMINING THE DEFLECTION OF THE FREE END FOR EACH WEIGHT. DELTA IS A FIRST-ORDER FUNCTION OF DENSITY CHANGE.

  • Supplemental Notes:
    • Vol 112, No 3, PP 206-212, 7 FIG, 4 REF
  • Corporate Authors:

    N/A

    ,   United States 
  • Authors:
    • Arulanandan, K
    • Smith, S S
  • Publication Date: 0

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Filing Info

  • Accession Number: 00230065
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Nov 1 1971 12:00AM