550
ELEMENTS OF MATERIA MEDICA.
fifteen grains, given in the form of solution every four or six hours.Ran gave as much as forty grains at a dose, and I have no doubt thatvery much larger doses may he given with safety.
Fer'ri Sulphas.—Sulphate of I'ron.
History. —Sulphate of iron is one of the substances which Pliny (Hist. Nat. xxxiv. 32) termed chalcanthum. This is evident from the cir-cumstance of his statement that the Romans called it atramentumsutorium, or shoe-makers black. It is frequently termed copperas, andin consequence has been sometimes confounded with the salts of copper(Dr. Cummin, Lond. Med. Gaz. xix. 40): green vitriol (vitriolum viride),vitriol of Mars (vitriolum martis), salt of Mars (sal martis), vitriolatediron (ferrum vitriolatum), are other names by which it has been known.
Natural History. —It is found dissolved in some mineral waters(sulphated chalybeates, vide p. 145), as those of the Ilartfell Spa, Scot-land . In the aluminous chalybeate waters it is associated with sulphateof alumina ; as in the water of Sand Rock, Isle of Wight . The strongMoffatt chalybeate, and Vicar ’s Brig chalybeate, contain the sulphate ofthe sesquioxide of iron. Sulphate of iron is also found in the watersof several copper mines.
Sulphate of the protoxide of iron is rarely met native in the crystal-lized state. It occurs, however, in Raminelsberg mine, near Goslar ; atSchwartzenburg, in Saxony; at Hurlet, near Paisley; and in NewEngland (Phillips’s Mineralogy , by Allan).
Dr. Thomson (Mineralogy) has described two native sulphates of thesesquioxide of iron, and an aluminous protosulphate.
Preparation. —Sulphate of the protoxide of iron is prepared by dis-solving clean unoxidized iron in diluted sulphuric acid. The propor-tions employed in the London Pharmacopoeia are eight ounces of ironfilings, fourteen ounces of sulphuric acid, and four pints of water. TheDublin Pharmacopoeia employs two pints more water.
In this process an equivalent or 28 parts of iron decompose one equi-valent or 9 parts of water, combine with an equivalent or 8 parts ofoxygen, and set free an equivalent or 1 part of hydrogen, which escapesin the gaseous form. The equivalent or 36 parts of protoxide iron, thusformed, combines with an equivalent or 40 parts of sulphuric acid, toform an equivalent or 76 parts of sulphate of iron.
REAGENTS.
RESULTS.
1 eq. Water
q 1 ' eq- Hydrogenv ^leq. Oxygen ..
1-leq. Hydrogen. I
$1 eq. Protoxide Iron 36'—_
0- , ■.■-... TTr . ^1 eq.Sulphate of Iron 76
The common green vitriol, or copperas of the shops, is prepared byexposing heaps of moistened iron pyrites (bisulphuret of iron) to the airfor several months. In some places the ore is previously roasted. Themoistening is effected by rain or by manual labour. The pyrites attractsoxygen, and is converted into a supersulphate of iron, which is dis-solved out by lixiviation; and to the solution thus obtained old iron isadded to saturate the free acid. It is then concentrated in leaden boilers,and run off into large vessels (lined with lead) to crystallize.
Properties. — Sulphate of the protoxide of iron crystallizes in