The correct use of the pH meter electrode and precautions
Asbestos was added as an common ingredient to Brake Pads post-WWI, as car speeds began to increase, because research showed that its properties allowed it to absorb the heat (which can reach 500 °F) while still providing the friction necessary to stop a vehicle. However, as the serious health-related hazards of asbestos eventually started to become apparent, other materials had to be found. Asbestos brake pads have largely been replaced by non-asbestos organic (NAO) materials in first world countries. Today, brake pad materials are classified into one of four principal categories, as follows:
Non-metallic materials - these are made from a combination of various synthetic substances bonded into a composite, principally in the form of cellulose, aramid, PAN, and sintered glass. They are gentle on rotors, but produce a fair amount of dust, thus having a short service life.
Semi-metallic materials - synthetics mixed with varying proportions of flaked metals. These are harder than non-metallic pads, more fade-resistant and longer lasting, but at the cost of increased wear to the rotor/drum which then must be replaced sooner. They also require more actuating force than non-metallic pads in order to generate braking torque.
Fully metallic materials - these pads are used only in racing vehicles, and are composed of sintered steel without any synthetic additives. They are very long-lasting, but require more force to slow a vehicle while wearing off the rotors faster. They also tend to be very loud.
Ceramic materials - Composed of clay and porcelain bonded to copper flakes and filaments, these are a good compromise between the durability of the metal pads, grip and fade resistance of the synthetic variety. Their principal drawback, however, is that unlike the previous three types, despite the presence of the copper (which has a high thermal conductivity), ceramic pads generally do not dissipate heat well, which can eventually cause the pads or other components of the braking system to warp.However, because the ceramic materials causes the braking sound to be elevated beyond that of human hearing, they are exceptionally quiet.
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1. Before measuring the medium, it should be noted that there should be no air bubbles in the front of the bulb.
2. After the electrode is removed from the soaking bottle, it should be shaken and dried in deionized water. Do not use a paper towel to wipe the bulb. Otherwise, the electrostatic charge will transfer to the glass film, which will prolong the stable time of the potential. A better method is to use the electrode. Test solution rinse electrode.
3. After the pH compound electrode is inserted into the solution to be measured, it should be stirred and shaken for a few times before being placed still. This will speed up the response of the electrode. In particular when using plastic shell pH composite electrodes, the stirring and shaking should be severe, because there will be a small cavity between the bulb and the plastic shell. After the electrodes are immersed in the solution, the gas in the cavity will be too late to exclude air bubbles and make the ball. The bubble or liquid junction is in poor contact with the solution, so it must be stirred vigorously to remove air bubbles.
4. After testing in a viscous sample, the electrode must be washed several times with deionized water to remove the sample adhered to the glass film. Sometimes it is necessary to wash the sample with other solutions first, then wash it off with water, and dip in the soaking solution to activate it.
5. Avoid contact with strong acids and alkalis or corrosive solutions. If such solutions are tested, immersions should be minimized and carefully cleaned after use.
6. Avoid use in dehydrated medium such as anhydrous ethanol, concentrated sulfuric acid, etc. They can damage the hydrated gel layer on the surface of the bulb.
7. The shell material of the plastic shell pH composite electrode is polycarbonate plastic (PC). PC plastic will dissolve in some solvents, such as carbon tetrachloride, trichloroethylene, tetrahydrofuran, etc. If the test contains the above solvents, it will Damage to the electrode housing. Use a glass-encapsulated pH composite electrode instead.