Vertical Soil Extensometer

Abstract

A vertical soil extensometer was developed to measure differential soil movement between two reference points. The extensometer incorporates telescoping casing sections installed in a bore hole with the aid of a section spacing device. The length of the casing can thus expand and contract with the soil. Connecting pipes inside the casing transfer upper and lower anchor movements to an electrical sensor, without interference from the soil around the casing. The extensometer is easily fabricated from standard materials and purchased components. This paper is intended to provide enough details to enable the reader to construct the device. Installation procedures are also presented.

Potentiometric titration of sulfate with lead and barium ions with various indicating electrodes

“…In previous work (Selig, 1983), we have found that a platinum electrode (without any conditioning or pretreatment) as well as many types of graphite rods may serve as suitable sensors in the potentiometric titration of fluoride. This work is extended here to the titration of sulfate vs. lead or barium ions.…”

“…All titrations were performed in an 80% methanolic medium, because even the lead ISE showed poor response in an aqueous medium at the low levels of sulfate examined. Preliminary experiments were performed with various electrode couples found successful in the titration of fluoride (Selig, 1983) and suggested by Schumacher et al (1982) for the titration of sulfate. The results are summarized in Table I.…”

“…Pretreatment of graphite sensors with permanganate was found to be beneficial in enhancing end-point breaks in acid-base and redox titrations (Pastor et al, 1978) and in the titration of fluoride vs. lanthanum(HI) (Selig, 1983). This also applied to the titration of sulfate vs. lead(II) and barium(II).…”

“…We consider the results good enough to warrant consideration of the graphite rods as sensors for the sulfate titration. Another consideration is their low cost as well as their applicability in other types of potentiometric titrations (Selig, 1982(Selig, , 1983).…”

“…Mixed oxide electrodes were recently used (Schumacher et al, 1982) to monitor the precipitation titration of sulfate vs. lead(II) or barium(II) in partially nonaqueous media. Our recent work (Selig, 1983) has shown that the potentiometric titration of fluoride vs. lanthanum(III) or thorium(IV) can be monitored with sensors other than the fluoride ISE. Indeed, even platinum as well as a variety of graphite sensors can accomplish this purpose.…”