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A Comparison of the Hydrometer Method and the Pipette Method for Making Mechanical Analysis of Soils, with New Directions 1
Author(s) -
Bouyoucos George John
Publication year - 1930
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1930.00021962002200080011x
Subject(s) - george (robot) , citation , soil water , pipette , section (typography) , library science , computer science , operations research , mathematics , environmental science , chemistry , artificial intelligence , soil science , operating system
A comparison has been made between the hydrometer method and the pipette method and it has been found that what the pipette method determines as clay (0.005-000 ram) and the finer clay (o.oo2ooo mm), the hydrometer method will determitm in ~ and 2 hours, respectively, even though theoretically it should take a much longer time. This comparison has been checked by the United States Bureau of Chemistry and Soils, and the results obtained go to shoxv that the two methods agree very closely with few exceptions. It would, seem, therefore, that the hydrometer method can be used with confidence for making mechanical analysis of soils for all practical purposes. The final procedure as developed up to date for making mechanical analysis of soils by the hydrometer method, is as follows: Add 5o grams of the fine textured soils and ioo grams of the sand, based on oven-dry condition, to the dispersing cup. Fill the cup with distilled water to about ~ y~" inches from the top. Add to the contents 5 cc of a solution of saturated and filtered sodium oxalate and 5 cc normal sodium hydroxide. If the soil is in lumps, suff~cient time must be given to it to slake and to soak..k s a matter of fact, it is well to allow all soils to soak for about ~ 5 minutes before dispersing them. The soils should always be air dry, because in the wet condition they do not slake. The soaking can be done in a separate vessel and the material then washed into the cup. Then connect the cup to the stirring motor, and stir the contents for 5 minutes in the case of sands, and ~o minutes in the case of all other soils. Those soils, however, which are recognized as difficult of dispersion should be dispersed for 2o to 3o minutes, or longer~ The sands should not be stirred more than 5 minutes because they seem to undergo grinding. Pour and wash the contents into the special cylinder. If 50 grams of soil are used, fill the cylinder up to the lower mark with the hydrometer in it. If ~oo grams of soil are used, fill it to the upper mark with the hydrometer in it. Only distilled water should be used. Then take the hydrometer out, place the palm of one hand on the mouth of the cylinder and shake the contents vigorously, turning the cylinder upside down and back several times. Place the cylinder