Preparation of battery acid. A 2.5 beaker is essential…3 I, preferably high and small diameter and a float device for measuring the density of liquids, called a hydrometer, with a scale range from 1,20 do 1,30 g/cm3. In case of using an older type hydrometer, with a scale in degrees Baume (Be), scale must range from 25 do 35 Be. In order to receive 1000 cm3 of battery acid with a density 1,24 g/cm3, must be carefully measured with a measuring cylinder 780 cm3 distilled water (for density 1,28 – 740 cm3 of water), transfer it to the beaker, dry the cylinder and measure in it 218 cm3 of concentrated sulfuric acid with purity p.a., which means clean for analysis (to obtain the density 1,28 – 257 cm3 of acid). Pour the acid into the water in a thin stream, constantly stirring with a glass rod. To prevent the solution from heating up too much, the addition of acid should be stopped for several minutes after adding every 50…60 cm3 of acid. In this phase of work, the use of protective glasses is absolutely essential.
After all the measured volume of acid has been poured into the water, drain, also for water, residual acid from the walls of the measuring cylinder and allow the solution to cool to room temperature for several hours (20°C). Check the temperature with a thermometer. Measure the density with a hydrometer. If all steps were performed carefully, the resulting solution will have a slightly higher density than desired. Bring the solution to the proper density by carefully adding small volumes of distilled water, stirring constantly and waiting for the reading of the density each time until the temperature drops again. do 20°C. Density 1,24 g / cm3 corresponds to 27.9 ° Be, density 1,28 g/cm3 – 31,5°Be.