Chrome alum can be purchased at various online retailers such as Amazon, eBay, and specialty chemical suppliers. It may also be available at local craft stores, art supply stores, or specialty chemical stores. Additionally, some pharmacies or drugstores may carry chrome alum as well. **

Pure chrome alum can be purchased from chemical supply companies, specialty online retailers, or scientific equipment suppliers. It is important to ensure that the source is reputable and provides high-quality, pure chrome alum. Additionally, it may also be available at some local specialty stores that cater to artists, craftsmen, or scientific researchers. **

Alum is not necessary for lilac-red hydrangeas. The color of hydrangea flowers is determined by the pH level of the soil. For lilac-red hydrangeas, the soil should be slightly acidic with a pH level of around 5.5 to 6.5. Adding alum to the soil can lower the pH level and help achieve the desired color, but it is not necessary if the soil already has the appropriate pH level. Regularly testing and adjusting the soil pH is the key to achieving the desired color for hydrangeas. **

To make crystals using alum, start by creating a supersaturated solution of alum by dissolving alum powder in hot water. Stir the solution until no more alum can dissolve. Then, pour the solution into a clean container and suspend a seed crystal (a small piece of alum) in the solution using a string or fishing line. As the solution cools, the alum molecules will come together and form crystals around the seed crystal. After a few days, carefully remove the crystals from the solution and allow them to dry. **

Alum belongs to the class of substances known as double salts. These salts are formed when two different salts are crystallized together, typically involving a combination of an alkali metal sulfate and an aluminum sulfate. Alum is commonly used in various industrial and household applications, including as a mordant in dyeing, in water purification, and in pickling. **

To grow crystals with alum, it is important to dissolve the alum completely in hot water before allowing it to cool and form crystals. Using a clean container and a seed crystal can help jumpstart the crystallization process. Additionally, be patient as the crystals can take several days to form. Finally, avoid disturbing the container once the crystals start forming to prevent disrupting their growth. **

The reaction equation of clay with alum is as follows: Al2(SO4)3 + 2Al(OH)3 + 8H2O → 2Al(OH)4 + 3H2SO4 In this reaction, aluminum sulfate (Al2(SO4)3) reacts with aluminum hydroxide (Al(OH)3) in the presence of water to form aluminum hydroxide (Al(OH)4) and sulfuric acid (H2SO4). This reaction is commonly used in the process of clarifying water by removing impurities and suspended particles. **

The crystal growth of potassium alum is carried out through a process called crystallization. First, a saturated solution of potassium alum is prepared by dissolving the compound in hot water. The solution is then allowed to cool slowly, which causes the potassium alum molecules to come together and form solid crystals. As the solution cools, the molecules arrange themselves in an orderly, repeating pattern to form the characteristic crystal structure of potassium alum. The crystals can then be harvested from the solution and further purified if necessary. **