Sulfuric acid relative density

Sulfuric Acid (relative density 1.84)—Concentrated sulfuric add (H2SO4). 

The fibers of aromatic PODs are known to have a combination of good properties, such as strength and stiffness, fatigue resistance, and relatively low density, in the range of 1.2 to 1.4 g/cm3. PODs have been used to improve the heat resistance of many synthetic fibers. This is usually done by dissolving the POD in sulfuric acid and then treating the fibers with this solution. Poly( >-phenylene-l,3,4-oxadiazole) is the most commonly used commercial polyoxadiazole, and the fiber spun from this polymer is called Oksalon. 

The method of carrying out kinetic runs depends upon the rate of nitration and the temperature. For relatively slow reactions at or near room temperature, the easiest procedure is to carry out the reaction in a volumetric flask to which are added a weighed amount of substrate (—40 mg), sulfuric acid of known composition nearly to the mark, and, finally, a measured excess (—0.5 g) of —70% nitric acid. Urea (one-tenth of the molar concentration of nitric acid) must also be added to prevent nitrosa-tion. The flask is then placed in a thermostatted bath and, at appropriate intervals, portions are removed, quenched, and the optical density measured. For kinetic runs above 50°C the procedure differs only in that aliquots are sealed in Pyrex tubes before thermostatting. 

The Tafel equation also describes the evolution of oxygen at a platinum anode. Bockris and Huq found that, with solutions carefully purified by preelectrolysis, the oxygen electrode exhibits reversible behavior (E = 1.24 V, compared with the theoretical 1.23 V). The exchange current density, however, is only of the order of 10" to 10" °A/cm in dilute sulfuric acid so polarization occurs readily, and relatively large overpotentials are observed at moderate current densities. In solutions of ordinary chemical purity the Nemst relation fails for the oxygen electrode because of mixed-potential behavior. Criddle, using platinum electrodes in highly purified 1 M KOH, obtained a rest potential of 1.59 V. The potential is reduced by peroxide, which may be formed with impurities such as metals, protein, or carbon. 

In 1783, the French physicist Jacques Charles supervised and took part in the first human flight in a hydrogen balloon. Such balloons rely on the low density of hydrogen relative to air for their buoyancy. In Charles s balloon ascent, the hydrogen was produced (together with iron(II) sulfate) from the action of aqueous sulfuric acid on iron filings. 

In a subsequent paper, electrodeposition of rhenium species from sulfuric acid solutions of perhhenic acid onto polycrystalline Pt and Au surfaces was carried out both in underpotential and overpotential regimes. Metallic Re could be obtained by applying relatively high cathodic current densities, whereas Re(IV) compounds were more likely to form in reduction of ReO4 at low current densities. Lastly, the deposition of rhenium species on Au from Re2O7 containing sulfuric acid solutions was studied. It was shown that the chemical nature of electrodeposited rhenium... 

FM3. Acid stratification. On recharge, sulfuric acid is produced in and between the plates and there is a tendency for acid of higher concentration, which has a greater relative density, to collect at the bottom of the cell, see Fig. 1.3 [7]. 

Some RAPS facilities are located in Arctic and Antarctic regions where the dark season can last for several months and the temperature can drop below — 50°C. Obviously, batteries installed in PV-powered RAPS systems in these regions can experience low SoCs at sub-zero temperatures for extended periods of time. As might be expected, the two main failure modes of batteries operated under such duty are sulfation of the active material and freezing of the electrolyte [26]. The latter mode is particularly prevalent when the battery is in a discharged state. This is because the temperature at which sulfuric acid freezes increases with decreasing relative density. (Note, it is quite unusual for a fully charged battery to experience this problem.)... 

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