Dry cleaning is the process of cleaning fabrics without water. Special solvents and soaps are used so as not to harm fabrics. The practice began in France in the middle of the 19th century, after a dye-works owner noticed that his tablecloth became cleaner after his maid spilled kerosene on it. Early solvents were extremely flammable and led to many fires and explosions. Newer chlorinated hydrocarbon synthetic solvents, such as perchlorethylene, are nonflammable but pose what other dangers? Discuss