Solutions of muriate of lime and carbonate of potash will answer as well.
TO FORM A LIQUID FROM TWO SOLIDS.
Rub together in a Wedgewood mortar a small quantity of sulphate of soda and acetate of lead, and as they mix they will become liquid.
Carbonate of ammonia and sulphate of copper, previously reduced to powder separately, will also, when mixed, become liquid, and acquire a most splendid blue colour.
The greater number of salts have a tendency to assume regular forms, or become crystallised, when passing from the fluid to the solid state; and the size and regularity of the crystals depends in a great measure on the slow or rapid escape of the fluid in which they were dissolved. Sugar is a capital example of this property; the ordinary loaf-sugar being rapidly boiled down, as it is called: while to make sugar-candy, which is nothing but sugar in a crystallized form, the solution is allowed to evaporate slowly, and as it cools it forms into those beautiful crystals termed sugar-candy. The threads found in the centre of some of the crystals are merely placed for the purpose of hastening the formation of the crystals.
EXPERIMENTS.
1. Make a strong solution of alum, or of sulphate of copper, or blue vitriol, and place in them rough and irregular pieces of clinker from stoves, or wire-baskets, and set them by in a cool place, where they will be free from dust, and in a few days crystals of the several salts will deposit themselves on the baskets, &c.; they should then be taken out of the solutions, and dried, when they form very pretty ornaments for a room.
2. Fill a Florence flask up to the neck with a strong solution of sulphate of soda, or Glauber’s salt, boil it, and tie the mouth over with a piece of moistened bladder while boiling, and set it by in a place where it cannot be disturbed. After twenty-four hours it will probably still remain fluid. Pierce the bladder covering with a penknife, and the entrance of the air will cause the whole mass instantly to crystallize, and the flask will become quite warm from the latent caloric, of which we have spoken before, given out by the salt in passing from the fluid to the solid state. It is better to prepare two or three flasks at the same time, to provide against accidents, for the least shake will often cause crystallization to take place before the proper time.
CHANGES OF COLOUR PRODUCED BY COLOURLESS LIQUIDS.
Make a strong infusion of the leaves of the red cabbage, which will be of a beautiful blue colour; drop into it a few drops of dilute sulphuric acid, and the colour will change to a bright red; add some solution of carbonate of potash, or soda, and the red colour will gradually give way to the original blue; continue adding the alkaline solution, and the fluid will assume a bright green colour. Now resume the acid, and as it is dropped in, the colour will again change from green to blue, and from blue to red. Now this simple experiment illustrates three points: first, that acids change the colour of most vegetable blues and greens to red; second, that alkalies change most blues and reds to green; and third, that when the acid and alkali are united together, they both lose their property of changing colour, and become what is called a neutral salt, i. e. a compound possessing the properties of neither of its constituents.