Final answer:
To clear up a milky solution resulting from the hydrolysis of aluminium sulphate, you should control the pH by adding more dil. sulfuric acid cautiously. If the precipitate is formed, redissolving it may require high temperatures to convert it into soluble aluminum oxide, or there may be a need for improved filtration to remove insoluble impurities.
Step-by-step explanation:
When trying to obtain a clear solution from aluminium sulphate and water that turns milky due to the hydrolysis of aluminium sulphate to aluminium hydroxide, you are facing a chemical reaction where the aluminium ions react with water to form a precipitate. To prevent this, you might try to make sure the acidity (pH) of the solution is properly controlled such that hydrolysis is minimized. If the milky appearance is due to the formation of aluminum hydroxide, you can add more dil. sulfuric acid in small quantities to try and redissolve the precipitate. This is based on the principle that the addition of acid to the aluminate leads to the dissolution of aluminum hydroxide.
If adding dil. sulfuric acid does not work, it might be that the aluminum hydroxide has been formed and can only be dissolved under specific conditions. One way to redisolve aluminum hydroxide is to subject it to high temperatures where it converts to aluminum oxide, which is then soluble in a molten mixture of cryolite and calcium fluoride. However, this process is beyond the scope of usual laboratory exercises and is typically involved in industrial aluminum extraction.