126

ELEMENTS OF MATERIA METIICA.

of heat and iron, or of sulphuric acid and a metal (zinc or iron). Thelatter method only will require notice here.

Add some granulated zinc to a mixture of 1 part sulphuric acid and 5 or6 parts of water by measure. One equivalent or 32 parts of zinc decomposeone equivalent or 9 parts of water, and unite with one equivalent or 8 partsof the oxygen, forming one equivalent or 40 parts of the oxide of zinc,while an equivalent or 1 part of hydrogen is evolved from the water.This equivalent of oxide of zinc combines with an equivalent or 40 partsof sulphuric acid, and forms one equivalent or 80 parts of the sulphate ofzinc.

INGREDIENTS USED.

1 eci Water Q 5 1 er l' Hydrogen 1_

1 eq. water . y j j ^ Oxygen.. 8;

1 eq. Zinc.32$

1 eq. Sulphuric Acid.40_

1 eq. Oxide Zinc 4C-*

PRODUCTS.

1 eq. Hydrogen . 1

Sulp te . Zinc 80

1 eq. Hydr.=1

1 eq.

Oxyg.=8

It is remarkable that zinc alone does not decompose water, but sulphuricacid enables it to do so.

Properties. —Hydrogen is a colourless, tasteless, and, when pure,odourless gas. Its sp. gr. is 0'0694,—so that it is 14 4 times lighter thanatmospheric air. Its refractive power is very high. It is combustible,burning in atmospheric air or oxygen gas with a pale flame, and formingwater. It is not a supporter of combustion. It is a constituent of somepowerful acids, as the hydrochloric, and of a strong base, ammonia. Itsatomic weight or equivalent is 1. Its atomic volume is also 1.

Characteristics. —It is recognised by its combustibility, the pale

colour of its flame, its not support-forming; i eq. ivater= 9 . combustion, and by its yieldingwhen exploded with half its volumeof oxygen, water only.

Physiological Effects, (a.) On vegetables. —Plants which are deprivedof green or loliaceous parts, or which possess them in small quantity only,cannot vegetate in hydrogen gas : thus seeds will not germinate in thisgas: but vegetables which are abundantly provided with these partsvegetate for an indefinite time in hydrogen (Saussure, Recherches Chem.sur la Vtget. pp. 195 and 209). Applied to the roots of plants in theform of gas, it is injurious (ibid. p. 105,) but an aqueous solutionof it seems to be inert (Decandolle, Physiol. Veg'et. t. iii. p. 1360). Ithas been said that when plants are made to vegetate in the dark theiretiolation is much diminished, if hydrogen gas be mixed with the airaround them; and in proof of this Humboldt has mentioned severalgreen plants found in the Freyberg mines (Thomson’s Syst. of Chemistry ,6th ed. p. 347-8.)

(b.) On animals generally .— Injected into the jugular vein of a doghydrogen produces immediate death, probably from its mechanical effectsin obstructing the circulation and respiration (Nysten, Recherches, p. 10.)

(c.) On man. —It may be breathed several times without any injuriouseffects. Scheele made twenty inspirations without inconvenience. Pilatrede Rozier frequently repeated the same experiment, and to shew that hislungs contained very little atmospheric air he applied his mouth to atube, blew out the air, and fired it, so that he appeared to breathe flame.If much atmospheric air had been present detonation must have taken