486
ELEMENTS OF MATERIA MEDICA.
Composition. —If this compound be, as Mr. Brande {Man. of Pharm.3d ed. 329) supposes, a mixture of bisulphuret of mercury and sulphur,the proportions must be—
Purity. —Free mercury may be detected by its communicating a whitestain to gold. Charcoal may be detected by its not volatilizing by heat.Animal charcoal, by this character, as well as by the presence of phos-phate of lime in the residue {vide p. 359). Sesquisulpliuret of antimonymay be recognised by boiling in hydrochloric acid, and applying thebefore-mentioned (p. 400) tests for sesquichloride of antimony.
Physiological Effects. —According to the experiments of Orfda, thispreparation, like the last, possesses little or no activity. The late Dr.Duncan {Edinb. Dispensatory) also tells us, that he has given it in dosesof several drachms, for a considerable length of time, with scarcely anyeffect. It is commonly regarded as alterative.
Uses.- —It has been used in glandular diseases, especially of children;and also in cutaneous diseases.
Administration. —The dose for adults is from 5 to 30 grains.
Hydrargyri Bicyan'idum. — Bicy’anide of Mer’cury.
History. —This salt was discovered by Scheele. Its real nature wasfirst pointed out by Gay-Lussac in 1815. It has been known by variousappellations, as Prussian mercury {hydrargyrum borussicum ), prussiate,hydrocyanate, cyanuret, or cyanodide of mercury {hydrargyri prussias,hydrocyanas, cyanuretum, seu cyanodidum ).
Preparation. —Two methods have been adopted for the preparationof it.
{a.) Proust's process. —In the Pharmacopoeia , eight ounces of ferro-sesquicyanide of iron, or Prussian blue (ferri percyanidum, Ph . L.) aredirected to be boiled with ten ounces of binoxide of mercury and fourpints of water. The mixture is to be strained and evaporated, so that itmay crystallize. The undissolved residuum is to be washed with boilingdistilled water, filtered, and evaporated, so as to yield crystals.
REAGENTS.
2 eq. Ferrosesqui- W Protoc ^ n - Iron ■ 163 ^3 &T £cyan. Iron 430^ eq . Sesquicy . Iron .. «, {« £ ff] jf
( 4£ eq. Mer. 90!
4£ eq. Binoxide of Mercury .981 <3 eq.Oxyg. 24■
(6 eq.Oxyg. 48-
RESULTS.4£ Bicyan. Merc. '
3 eq. Oxide Iron .
4 eq. Sesquioxide
of Iron ..
108 ’l.l160 j |
The awkwardness of the use of half an equivalent may be easilyobviated by doubling all the above numbers; but several reasons haveinduced me to retain it in the above diagram.
{b.) Winckler’s process. —Bicyanide of mercury may be obtained moreeconomically, and purer, by adding as much finely-pulverized binoxideof mercury to hydrocyanic acid (obtained by distilling ferrocyanide ofpotassium with diluted sulphuric acid, vide p. 236) as will saturate it,