Calibrrticn of the - 12 - D. M. Poole and 



Einery Settling Tube W. S. Butcher 



for Srnd /jic.lysls 



surface crm be mrde to sink by touching thera with o. wooden pencil. The scuid 

 can then be released into the tube. Care must be taken when introducing very 

 fine sand that large density currents do not form. This may be accomplished 

 by slightly tilting the introd.ucing tube and allowing a portion of the sfJid to 

 enter the settling tube slowly, followed inuTiediately by the bulk of the sample. 

 Tapping the upper part of the tube will help brerk up any density currents 

 that form. 



Several runs were made with very fine sand spjuples using disaggregating 

 agents, sodium oxalate (Na2C20,) cjid sodium hexametaphosphate (Na^(PO^)^), to 

 wet the sand before introduction into the tube. The results were not signifi- 

 cantly different from splits of the same saiaples which were wet with distilled 

 water. 



It was noted at times that the distilled water added to the tube contained 

 fine bubbles. This bubble formation occurred when the distilled water supply 

 was low enough to cause eomewhat intenaittent flow. Flocculation, by adsorp- 

 tion to the bubbles, occurs when the bubbles are quite small and numerous. 

 Since such adsorption makes the analysis erroneous, it is advisable thrt no runs 

 be made while such bubbles exist. 



The temperature of the distilled water is measured by running the water 

 from the outlet through a bottle containing a thermometer and then into the 

 settling tube. At present, the water is led in and out through two holes in a 

 cork fitting a small wide-mouthed bottle. The thermometer is held in a third 

 hole so that its bulb is bathed by the flowing water. 



Reading the Height of Sand ; The stopcock stem, gradurted in iTiilliliters, 

 is not tapped as recomraended by Emery (1938). Compaction was seH om observed 

 in the sand column if the sand particles greater than 1 mm, were removed, but 



