Mononymous self-described “citizen scientist” Marb, of YouTube channel Marb’s Lab, has demonstrated construct your personal pH meter for measuring acidity and alkalinity — offered you are assured with glassworking and have some antimony and a graphite crucible at hand.
“[This pH meter design] could be appropriate for a lab on a chip,” Marb says of his creation, “as it may be miniaturized. It has already been utilized in medication as a gastric probe, to measure the pH worth of abdomen acid, [and] additional functions in medication could be to measure the pH worth of blood or urine.”
A standard potentiometric pH mater has a reference electrode and a glass electrode, however Marb’s construct opts for a special design that swaps the glass electrode for antimony — identified for its simplicity and reliability in harsh situations, although with the caveat that it affords decrease accuracy than conventional designs.
The transfer to antimony doesn’t suggest Marb’s pH meter has no glass concerned, although: constructing the gadget entails slicing tubes of borosilicate glass and rounding their ends, then melting antimony in a graphite crucible — to forestall the formation of antimony trioxide — earlier than drawing it up right into a glass tube. The reference electrode, made utilizing a copper-copper(II) sulfate, is considerably easier, needing solely a little bit epoxy to safe it within the tube earlier than filling it with copper sulphate and sealing it with a potassium-nitrate-treated picket dowel.
The manufacturing course of is, maybe, a little bit on the furry facet, producing carbon monoxide because the antimony is melted. (📷: Marb’s Lab)
The electrodes are linked to an Arduino-compatible microcontroller, then calibrated with fluids of identified pH worth. “Because the pH worth additionally will depend on temperature,” Marb provides, “the PCB additionally has a connector for a[n Analog Devices] DS18B20 temperature sensor with a large measuring vary.”
The mission is documented within the video embedded above and on Marb’s YouTube channel, full with a schematic for the electronics.