A Chemical Trick.

Progress, Volume II, Issue 3, 2 January 1907, Page iv (Supplement)

A Chemical Trick.

When we happen to witness a phenomenon which seems to violate natural laws, we are not likely to foiget its cause if it be explained to us. The following experiment, which I devised for my students (writes a Doctor of Science m the Scientific American) helped them to understand as well as to remember some chemical data. A white cat, made of flexible pasteboard and imprisoned in a glass jar, is shown to the audience The lecturer announces that, without opening the jar or even touching it, he will cause the cat to undergo a zoological, as well as a chemical, transformation. He takes the support of the jar, and pushes it forward in full view of the students. The change occurs almost instantaneously. The cat takes a rich orange colour on which black transversal stripes rapidly paint themselves. The cat has become a tiger. The whole transformation is produced by emanations of hydrogen sulphide, which is generated in the jar itself without any visible apparatus. The cat has been previously coated with a solution of chloride of antimony wherever the orange hue was to be produced, and with a solution of basic acetate of lead wherever the black strips were to appear. Both solutions are colourless After the coated cat has been introduced in its glass cage, a small piece of pasteboard is placed under the wooden support so as slightly to incline the jar forward. A few decigrammes of pulverised sulphide of iron folded in a piece of blotting paper are deposited behind the cat, on the elevated side of the bottom of the jar. Two or three cubic centimetres of diluted sulphuric acid are dropped ■with a pipette on the opposite side. When the performer wishes the transformation to take place, he takes the wooden support and pushes it forward as if he wanted to enable everybody to see better what is going to happen. By so doing he suppresses the slight inclination which kept the iron sulphide beyond the reach of the sulphuric acid. The gas is evolved, and the formation of the orange sulphide of antimony and black sulphide to lead takes place in a few second".