Manufactured in borosilicate glass with blue enamel markings.
| Product | |
| Code | Description |
| WJ.606 | Voltameter, ungraduated, glass parts only |
| WJ.607 | Voltameter, 50ml grad. glass parts only |
| WJ.608 | Platinum electrodes, per pair |
| WJ.609 | Carbon electrodes, per pair |
| WJ.610 | Safety clamp |
Please note that for a full kit you will need both the glass parts of the voltameter (graduated or ungraduated), and a pair of electrodes.
Usage
Guide
Hoffman voltam
eters are used for demonstrating the chemical composition of water by volume. The apparatus is filled with dilute sulphuric acid (approximately 1N) through the central funnel. The two stopcocks are o
pened briefly to remove the air from the graduated tubes. A DC curre
nt (6-12 volts works well) is passed through the electrodes. The cat
hode evolves oxygen and the anode hydrogen. Theoretically twice the volume of hydrogen is evolved than oxygen. However oxygen is much more soluble in water than hydrogen, so the measured amount tends to be lower than expected.
After 10 to 20ml of gas has been collected the stopcock can be opened to collect the gas in a small test tube. Each gas can be tested to show they are different: The hydrogen should burn with a squ
eaky pop when a lighted splint is applied to it, and the oxygen should relight a glowing splint.
It is important that there is a reasonable surface area of platinum to evolve gas at a rapid rate when a voltage is applied. Otherwise the collected volumes are small and the gasses are difficult to test for.