To prepare these solutions, purchase of a druggist a small quantity of the solid crystals of the substance needed for the experiment you wish to try. Dissolve the crystals in clear pure water, and keep the solution in a little bottle, labeled with the name. It is seldom that the solutions need be strong. When the crystal is a colored one, enough should be used to give the water a light tint, blue, yellow, or what it may be. None of these solutions will do any harm to the hands, unless there is a cut or a wound of any kind upon the skin. It is well also, not to let a drop of any of them fall upon the clothes, or upon furniture, for some of them will stain. And none of them should ever be tasted, or touched by the lips or tongue, many of them being acrid and even poisonous. With the acids still greater care is needed, the stronger acids being corrosive and poisonous. The greater portion of these substances must likewise not be smelled, as the fumes or vapors would affect the nostrils painfully. For the proper performance of these experiments with solutions, etc.,--at all events for the neatest and most elegant performance of them,--there should be obtained from the chemist's shop about a dozen test-tubes. These are little glass vessels, manufactured on purpose, and very cheap. Do not take glasses that may afterward be used for drinking or household purposes. Be careful to have every one of your experiment glasses perfectly clean. _To produce a Beautiful Violet-Purple Color._ Take a nearly colorless solution of any salt of copper. The sulphate is the cheapest and handiest. Fill the test-tube or other experimenting-glass about two-thirds full. Then drop in, slowly, a little liquid ammonia. It will cause a beautiful blue to appear, and presently a most lovely violet-purple, which, by stirring with a glass rod, extends all through the fluid. If now you drop into this a very little nitric acid, the fluid will again become as clear as pure water. _To Make a Splendid Scarlet._ Again take some solution of sulphate of copper. Add to it a little solution of bichromate of potash. Then add a little solution of nitrate of silver, and there is produced a splendid scarlet color. _To Make a Deep Blue._ Now, take a nearly colorless solution of sulphate of iron, and drop into it, slowly, a small quantity of solution of yellow prussiate of potash. This will induce a beautiful deep blue, quite different from the blues that are produced from copper salts. _To Make a Yellow Color._ Take a solution of acetate of lead, and add a few drops of solution of iodide of potassium, and a most lovely canary-yellow color is produced. _Invisible Inks._ Nearly all those experiments which result in the production of color may be performed in another way, and be then applied to the purposes of secret writing. Thus: Write with dilute solution of sulphate of copper. The writing will be quite invisible, but become blue when held over the vapor of liquid ammonia.