Read the excerpt from chapter 8 of The Strange Case of Dr. Jekyll and Mr. Hyde. Poole felt in his pocket and handed out a crumpled note, which the lawyer, bending nearer to the candle, carefully examined. Its contents ran thus: "Dr. Jekyll presents his compliments to Messrs. Maw. He assures them that their last sample is impure and quite useless for his present purpose. In the year 18—, Dr. J. purchased a somewhat large quantity from Messrs. M. He now begs them to search with most sedulous care, and should any of the same quality be left, forward it to him at once. Expense is no consideration. The importance of this to Dr. J. can hardly be exaggerated.” So far the letter had run composedly enough, but here with a sudden splutter of the pen, the writer’s emotion had broken loose. "For God’s sake,” he added, "find me some of the old.” Read the excerpt from chapter 10 of The Strange Case of Dr. Jekyll and Mr. Hyde. My provision of the salt, which had never been renewed since the date of the first experiment, began to run low. I sent out for a fresh supply and mixed the draught; the ebullition followed, and the first change of colour, not the second; I drank it and it was without efficiency. You will learn from Poole how I have had London ransacked; it was in vain; and I am now persuaded that my first supply was impure, and that it was that unknown impurity which lent efficacy to the draught. How does Dr. Jekyll’s confession answer questions about his desperate search for chemical salts?