On the various forces of nature and their relations to each other/Notes
NOTES.
LECTURE I.
(1) Page 13. The opening lecture was twice postponed on account of Dr. Faraday's illness.
(2) Page 22. Platinum, with one exception, the heaviest body known, is 21½ times heavier than water.
(3) Page 22. Aluminium is 2½ times heavier than water.
(4) Pages 23 and 24. Power or Property in Water.—This power the heat by which the water is kept in a fluid state—is said, under ordinary circumstances, to be latent or insensible. When, however, the water changes its form, and, by uniting with the lime or sulphate of copper, becomes solid, the heat which retained it in a liquid state is evolved.
(5) Page 23. Anhydrous Sulphate of Copper: sulphate of copper deprived of its water of crystallisation. To obtain it, the blue sulphate is calcined in an earthen crucible.
(6) Page 29. Add a little liquid to the marble, and decompose it.—Marble is composed of carbonic acid and lime, and, in chemical language, is called carbonate of lime. When sulphuric acid is added to it, the carbonic acid is set free, and the sulphuric acid unites with the lime to form sulphate of lime.
Carbonic acid, under ordinary circumstances, is a colourless invisible gas, about half as heavy again as air. Dr. Faraday first shewed that, under great pressure, it could be obtained in a liquid state. Thilorier, a French chemist, afterwards found that it could be solidified.
LECTURE II.
(7) Page 55. Crystallisation of Alum.—The solution must be saturated—that is, it must contain as much alum as can possibly be dissolved. In making the solution, it is best to add powdered alum to hot water as long as it dissolves; and when no more is taken up, allow the solution to stand a few minutes, and then pour it off from the dirt and undissolved alum.
(8) Page 57. Red Precipitate of Biniodide of Mercury.—A little care is necessary to obtain this precipitate. The solution of potassium should be added to the solution of perchloride of mercury (corrosive sublimate) very gradually. The red precipitate which first falls is redissolved when the liquid is stirred: when a little more of the iodide of potassium is added, a pale, red precipitate is formed, which, on the further addition of the iodide, changes into the brilliant scarlet biniodide of mercury. If too much iodide of potassium is added, the scarlet precipitate disappears, and a colourless solution is left.
(9) Page 57. Paper Coated with Scarlet Biniodide of Mercury.—In order to fix the biniodide on paper, it must be mixed with a little weak gum water, and then spread over the paper, which must be dried without heat.
Biniodide of Mercury is said to be dimorphous; that is, is able to assume two different forms.
(10) Page 59. "Prince Rupert's Drops."—These are made by pouring drops of melted green glass into cold water. They were not, as is commonly supposed, invented by Prince Rupert, but were first brought to England by him, in 1660. They excited a great deal of curiosity, and were considered "a kind of miracle in nature."
(11) Page 60. Thick Glass Vessels.—They are called Proofs or Bologna phials.
(12) Page 61. Mica..—A silicate of alumina and magnesia. It has a bright metallic lustre—hence its name, from mico, to shine.
(13) Page 62. Common salt, or chloride of sodium, crystallises in the form of solid cubes, which, aggregates together, form a mass, which may be broken up into the separate cubes.
(14) Page 62. Iceland or Calc Spar.—Native carbonate of lime in its primitive crystalline form.
LECTURE III.
(15) Page 79. Solution of a Salt.—Acetate of soda. A solution saturated, or nearly so, at the boiling point, is necessary, and it must be allowed to cool, and remain at rest until the experiment is made.
(16) Page 86. Cinoxide of Nitrogen and Hypo-nitrous Acid.—Binoxide of nitrogen is formed when nitric acid and a little water are added to some copper turnings. It produces deep red fumes as soon as it comes in contact with the air, by combining with the oxygen of the latter to form hypo-nitrous acid. Binoxide of nitrogen is composed of two parts oxygen and one part of nitrogen; hypo-nitrous acid is composed of one part of nitrogen and three parts of oxygen.
LECTURE IV.
(17) Page 106. Chlorate of Potash and Sulphuret of Antimony.—Great care must be taken in mixing these substances, as the mixture is dangerously explosive. They must be powdered separately, and mixed together with a feather on a sheet of paper, or by passing them several times through a small sieve.
(18) Page 107. The mixture of chlorate of potash and sugar does not require the same precautions. They may be rubbed together in a pestle and mortar without fear. One part of chlorate of potash and three parts of sugar will answer. The mixture need only be touched with a glass rod dipped in oil of vitriol.
(19) Page 107. Two Salts Dissolved in Water.—Sulphate of soda and chloride of calcium. The solutions must be saturated for the experiment to succeed well.
(20) Page 111. Lead Pyrophorous.—This is a tartrate of lead which has been heated in a glass tube to dull redness as long as vapours are emitted. As soon as they cease to be evolved, the end of the tube is sealed, and it is allowed to cool.
(21) Page 115. Gun-Cotton is made by immersing cotton-wool in a mixture of sulphuric acid and the strongest nitric acid, or of sulphuric acid and nitrate of potash.
(22) Page 115. Paper Prepared like Gun-Cotton.—It should be bibulous paper, and must be soaked for ten minutes in a mixture of ten parts by measure of oil of vitriol with five parts of strong fuming nitric acid. The paper must afterwards be thoroughly washed with warm distilled water, and then carefully dried at a gentle heat. The paper is then saturated with chlorate of strontia, or chlorate of baryta, or nitrate of copper, by immersion in a warm solution of these salts. (See Chemical News, Vol. I., page 36.)
LFCTURE VI.
(23) Page 162. Sulpho-indigotic Acid.—A mixture of one part of indigo and fifteen parts of concentrated oil of vitriol. It is bleached on the side at which hydrogen gas is evolved, in consequence of the liberated hydrogen withdrawing oxygen from the indigo, thereby forming a colourless deoxidised indigo. In making the experiment, only enough of the sulpho-indigotic acid must be added to give the water a decided blue colour.
(24) Page 164. Lead Tree.—To make a lead tree, pass a bundle of brass wires through the cork of a bottle, and fasten a plate of zinc round them just as they issue from the cork, so that the zinc may be in contact with every one of the wires. Make the wires to diverge so as to form a sort of cone, and having filled the bottle quite full of a solution of sugar of lead, insert the wires and cork, and seal it down, so as to perfectly exclude the air. In a short time the metallic lead will begin to crystallise around the divergent wires, and form a beautiful object.
THE END.