465
In tlie first stage of this process one equivalent or 202 parts of mer-cury decompose two equivalents or 80 parts of dry sulphuric acid; and,abstracting two equivalents or 16 parts of oxygen, to form one equivalentor 218 parts of binoxide of mercury, disengage two equivalents or 64parts of sulphurous acid. The binoxide combines with two equivalentsor 80 parts of undecomposed sulphuric acid, forming one equivalent or298 parts of bipersulphate of mercury.
REAGENTS.
2 e q .drySu,ph : ,f?^» r
A y .fH _ flA x 4 eq. Oxygen 32 ^-
Acid 2 eq. Oxygen 16 ?
1 eq. Mercury. 202 $ ^^Bmox.Mercury^X^
If one equivalent or 298 parts of bipersulphate, one equivalent or 202parts of reguline mercury, and two equivalents or 120 parts of chlorideof sodium, be intimately mixed and sublimed, reaction takes place, andwe obtain two equivalents or 476 parts of chloride of mercury, and twoequivalents or 144 parts of sulphate of soda.
REAGENTS.
2eq. ChlorideSodm. 120 {■>£}; ;
1 eq. Mercury
1 eq. Bipersulphate of_{ J 0xy£e7i
72
48
202
Mercury *=> 298 ^iric Acid si
RESULTS.
2 eq. Chloride Merc. = 476
--2eq.Sorfrt64 -
2 eq. Sulphate Soda == 144
Mr. Phillips {Translation of Pharmacopoeia , 1836) explains the processsomewhat differently. He assumes that the trituration of bipersulphatewith mercury converts this salt into the protosulphate of mercury, andthat this yields chloride of mercury by the action of chloride of sodium.But the mere trituration of bipersulphate of mercury with metallic mer-cury cannot be admitted to be sufficient to convert this salt into proto-sulphate. It is not improbable that bichloride of mercury is first formedby the mutual reaction of bipersulphate of mercury and chloride ofsodium ; and that this subsequently combines with mercury, both being-in the state of vapour, to form calomel. For some bichloride is alwaysfound mixed with the sublimed calomel, and calomel may be readilyobtained by subliming bichloride and mercury ; as in the process of theEdinburgh Pharmacopoeia.
At Apothecaries’ Hall, 50 lbs. of mercury are boiled with 70 lbs. ofsulphuric acid to dryness in a cast-iron vessel; 62 lbs. of the dry salt aretriturated with 401 lbs. of mercury, until the globules disappear, and 34lbs. of common salt are then added. The mixture is submitted to heatin earthen vessels, and from 95 to 100 lbs. of calomel are the result. Itis washed in large quantities of distilled water, after having been groundto a fine and impalpable powder.
The subliming apparatus varies in different manufactories. In someit consists of a large earthen retort, with short but wide neck, openinginto an earthen elliptical receiver, in the bottom of which is water.The retort is placed in sand, contained in an iron pot set in a furnace.
“ The form in which calomel sublimes,” observes Mr. Brande, “ de-pends much upon the dimensions and temperature of the subliming ves-sels. In small vessels it generally condenses in a crystalline cake, theinterior surface of which is often covered with beautiful quadrangularprismatic crystals (Brooke, Annals of Philosophy), transparent, and