Sherlock Holmes 'found a re-agent which is precipitated by haemoglobin, and by nothing else'. He then goes on to explain how this would have helped in the conviction of various criminals. (A Study in Scarlet)

 

Bartholomew's chamber was fitted up as a chemical laboratory. "A double line of glass-stoppered bottles was drawn up upon the wall opposite the door and the table was littered over with Bunsen burners, test tubes, and retorts. In the corners stood carboys of acid in wicker baskets. One of these appeared to leak or to have been broken, for a stream of dark-coloured liquid had trickled out from it, and the air was heavy with a peculiarly pungent, tarlike odour." (The Sign of Four)

 

Holmes tried to take his mind off the Bartholomew Sholto murder case by busying himself by heating retorts and distilling vapours until the early hours of the morning. (The Sign of Four)