2(54

ELEMENTS OF MATERIA MEDICA.

oxide of iron is left in the retort. If this acid be heated in a glassretort, it yields real or anhydrous sulphuric acid.

Properties, (a.) Of anhydrous sulphuric acid. —It is a crystallinesolid, having very much the appearance of asbestos. It gives out densewhite fumes in the air, like fluoride of boron. It melts at 66° F. andboils at from 104° to 122° F. The sp. gr. of the liquid acid, at 78° F.is T97.

(A.) Of the Nordhausen or fuming sulphuric acid. —This is usually adark brown oily-like liquid, w hich gives out copious white fumes in theair. Its sp. gr. is about T9. It is imported in stone bottles, having astonew'are screw for a stopper.

(c.) Of oil of vitriol or English sulphuric acid. —When pure it is acolourless, transparent, inodorous, highly acrid, and corrosive liquid. Itpossesses the usual properties of a powerful mineral acid in a veryeminent degree, such as reddening the vegetable blues, saturating bases,and displacing other acids. Its affinity for water is most intense, andby virtue of this, it absorbs aqueous vapour from the atmosphere, and charsanimal and vegetable substances. When mixed with water there is amutual condensation with the evolution of heat. Various substances whenheated in sulphuric acid decompose it; they abstract oxygen and evolvesulphurous acid. This is the case with charcoal, organic substances,phosphorus, sulphur, and several of the metals, as copper, tin, andmercury.

The sp. gr. of this acid at 60° F. is about V84. Genuine commercialacid should never surpass V8455; w r hen it is denser, we may infer sophis-tication or negligence in the manufacture (Braude’s Man. of Chemistry).Acid of sp. gr. T845 freezes at — 15° F. and boils at 620° F. In com-merce the acid has frequently a sp. gr. of only V8433, and its boilingpoint is 545° F. (Phillips’s Transl.)

Composition. —Pure or anhydrous sulphuric acid is thus composed:—

Eq. Eq.Wt. Per Cent. Berzel. Vol. sp. gr.

Sulphur ... 1 ... 16 ... 40 ... 40*14 I Sulphurous acid gas . . 1 . . 2*222

Oxygen ... 3 ... 24 ... 60 ... 59*86 I Oxygen gas .0*5 . . 0*555

Sulphuric acid 1 ... 40 . . 100 . - 100*00 | Sulphuric acid vapour .1? . . 2*777?

The composition of oil of vitriol or English sulphuric acid is as fol-

Strongest (sp. gr.

1-845)

Commercial (sp. gr

1-8433).

Eq.

Eq.Wt. Per Cent.

Eq.

Eq.Wt.

Per Cent.

Real sulphuric acid

i

. . . 40 ...

81-6

i .

. 40 ...

. 78

Water .

i

. . . 9 ...

18-4

if.

. 11-25 .

. 22

Oil of vitriol . .

i

. . . 49 ...

100-0

i .

. 51-25 .

. 100

According to this statement the strongest oil of vitriol which can be pro-cured (sp.gr. T845) is th % protohydrate of sulphuric acid, w r hile thatmet with in commerce is a \ hydrate of sulphuric acid.

The German or Nordhausen sulphuric acid consists of—

Eq. Eq.Wt. Per Cent. Eq. Eq.W r t.

Real sulphuric acid . . . . 2 . . 80 . . 89"887 (Real sulphuric acid .... 1 . 40

Water .1 . . 9 . . lO'llS ° ^Protohydrate sulphuric acid . 1 . 49

Nordhausen sulphuric A d . 1 . . 89 . . 99"99 (

1 . 89