"Nothing up my sleeve...": an antique text reveals some time-tested chemical illusions. (Chemfusion).
I learned about Heller's chemical conjuring from a marvelous book I received as a present. Scientific Mysteries and How to Produce the Most Interesting Chemical, Optical and Physical Illusions is for me a true treasure. Published in 1891 in London, the little volume is a compilation of various scientific effects that titillated Victorian audiences on the stage. Not only are some of the "tricks" truly ingenious, they also show clearly that those of us involved in performing chemical magic today may just be reinventing the wheel. A sobering thought.
Recently I purchased a gimmicked knife designed to create the illusion of slicing halfway through an arm. It came complete with a hidden bulb that could be filled with red food dye to squirt out at the appropriate moment. You may be wondering why I would be interested in such a gross item. There was some method to the madness. I had in mind to incorporate this illusion into a lecture on the history of charlatans, having learned that at one time mountebanks performed the trick and then pretended to heal the cut on their arm with whatever wondrous nostrum they were selling. Actually, I'm not sure how they produced the 'blood', because my gimmicked knife really didn't work well. The red dye didn't seem to come from the wound and worse than that, it made a big mess. So I put on my thinking cap and hoped to find a chemical solution to the problem. The challenge was to create the illusion of drawing blood with a knife.
Chemical analysis often involves various colour tests. Starch, for example, reacts with iodine to produce a deep blue colour, chlorine with toluidine produces yellow and iron reacts with potassium thiocyanate (KSCN) to form a blood red colour. The latter is a very sensitive reaction and is commonly used by criminologists to test for footprints. Most soils will contain some iron compounds which stick to the bottom of shoes. Footprints that are invisible to the naked eye can therefore often be visualized by spraying with a solution of potassium thiocyanate. Thinking that I was very clever, I decided to apply this reaction to my knife problem. I made a dilute solution of iron chloride (FeCl3) and rubbed some on my arm. After drying, it became invisible. Then I dipped the knife in a solution of potassium thiocyanate and was ready for the effect. I even had some patter for this, suggesting to the audience that the knife had to be disinfected before proceeding with the dangerous experiment. Lo and behold, it worke d! The illusion was amazing. The knife seemed to slice right into my arm, producing 'blood' appropriately. I was proud of my ingenuity.
Now of course I see that it had all been thought of before. My recently acquired hundred year-old book describes Robert Heller's illusion in detail. Using a camel hair brush dipped in "tincture of perchloride of iron," he drew the desired image on the lady's bare arm. Hidden in the magician's hand was a small bulb filled with a solution of "potassium sulphocyanide" (KSCN) which he sprayed on the arm while waving his hands around in the time honored fashion of magicians. And why did the lady have to be blindfolded? Simple. To protect her eyes from the chemical spray! As it turns out, this was not the only chemical trick performed by magicians of the era. My Scientific Mysteries describes a neat little illusion known as the 'Wonderful Bottle'. A brown glass bottle was tilted and shown to be empty. An audience volunteer was asked to fetch some water to fill it. Then in response to requests from the crowd, the magician would pour out port wine, claret, milk, champagne or ink. Everyone was flabbergasted! Actually , the bottle wasn't quite empty. A small amount of ferric chloride dissolved in hydrochloric acid had been placed in it. When the solution formed by adding water to this was poured into a glass that had a few drops of a concentrated potassium thiocyanate solution in it, 'port wine' was produced. A dilute solution of thiocyanate yielded 'claret'. Lead acetate reacts with ferric chloride to produce insoluble white lead chloride. So when the ferric chloride solution was added to a glass with a bit of lead acetate at the bottom, a white precipitate that passed for milk was produced. Champagne was created when hydrochloric acid reacted with baking soda (sodium bicarbonate) at the bottom of the glass. Treating baking soda with an acid produces copious amounts of carbon dioxide gas, the bubbles in champagne.
And the ink? That was easy as well. Ferric sulfide is black, so pouring the ferric chloride solution into a glass treated with ammonium sulfide resulted in ink. It undoubtedly also resulted in a rather disturbing smell. Ammonium sulfide readily releases hydrogen sulfide which is the memorable odour of rotten eggs. It is also a disturbing component of human fiatus. This notion has not been lost on the manufacturers of some modern novelties. 'Fa _ _ bombs' are packaged in little foil pouches that contain bicarbonate, ammonium sulfide and a bag of vinegar. When the pouch is squeezed, the vinegar is released and combines with the bicarbonate to generate carbon dioxide gas. In about ten seconds, enough pressure builds up to explode the foil pouch and release the fragrance of hydrogen sulfide. A novel discovery? Hardly. Leonardo da Vinci, who I bet you didn't know had chemical inclinations, designed stink bombs that could be launched with arrows! Plus a change, plus c'est pareil.
Joe Schworcz, MCIC, is the director of McGill University's Office for Science and Society. You con contact him at email@example.com
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|Publication:||Canadian Chemical News|
|Date:||May 1, 2003|
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