c:r 



MERCAPTIDES. 



MERCURY. 



Yinic mercaptau, wbiel> was the first investigated anil most important 

 of these compounds, and is frequently called m'-rrapfan. gives the name 

 to the series. The meroaptaus are colourless liquids, poaaessing a 

 hon-ibly foetid alliaceous odour. They act like acids upon metallic 

 oxides, forming m-rrapt itlc*. This i* especially so in the case of 03 ''!> 

 of mercury, hence the origin of the name la-rfuriifn cap/mis. The 

 following are the chief known mercaptans : 



Methyl mcrcnjitan 

 Kthyl mcrcaptan 

 Amyl mcrcaptan 



) 



MERCAPTIDES. [MKRCAPTANS.] 



MERCATOR'8 PROJECTION. [MAP.] 



MERCHANT SEAM EX. [Snips.] 



MERCHANT SHIPPING. [Snips.] 



M KltCURIAMIXE. [Mi-ncrnY.] 



MERCURY (Hg.) QtaflMver. The history of this well-known 

 metal, a description of the sources whence it is obtained, its physical 

 properties, and a list of the minerals in which it occurs have already 

 been given under MKRCUKY, in NAT. HIST. Div. An interesting 

 statistical account of the most important of all the mercury mines, 

 namely, those of Almaden in Spain, is also given under ALMADEX in 

 (iiiin. Div. It is here, therefore, only necessary to treat of its 

 chemical properties and the action of various substances upon it by 

 virtue of which compounds of the metal are obtained. 



The equivalent of mercury is 200. By combining with one or with 

 two equivalents of other bodies it forms two classes of salts, known as 

 protosa/tx and A/'xa/'.i. Sometimes the equivalent of mercury is assumed 

 to be 100, and then the first class of salts containing two such equiva- 

 lents to one of another body are necessarily termed disalts or sutsalts ; 

 while the second class, containing only one such equivalent to each 

 oquivalent of another body, are consequently termed jirotusalts. This 

 want of uniformity in the nomenclature of salts of mercury is to be 

 deprecated, inasmuch as it is confusing to students, and has also 

 frequently led to serious errors when employed by those who, like 

 medical men and compounders of medicine, have necessarily but a 

 partial knowledge of chemistry. A method now very generally 

 adopted, by which the inconvenience is obviated, consists iu adding 

 to the word merrur the terminals that are commonly used for similar 

 purposes namely, ic and ous. The first or lower class of salts are 

 thus mercur'n'x salt, and the second, or higher, mercuric salts. 



Mercury and oxy;/i:n form two compounds. 



1 . Protoxide of mercury ..... IlgO 



2. Binoxide of mercury BgO, 



1. Protoxide of mercury (HgO). Black oxide, grey oxide, ndjoxide, 

 or diuoxiilf, nf Hirrrury. Mercurous oxide. This oxide is best obtained 

 by triturating calomel with dilute caustic potash or soda, and well 

 washing and drying the resulting oxide. The operation should be 

 conducted as much as possible in the dark, as the oxide is decomposed 

 by the influence of light, into metallic mercury and binoxide. Though 

 itself unstable, it forms very stable salts, called tails of mercurous 

 oxide or shortly, mercurum salts. 



'2. Jliiinxidr i ,f mrri-iiry (HgO..). Peroxide, red oxide, yellow oxide, 

 or /,/',/., ;</!', of mercury. Mnvitric oxide. This oxide may be made ill 

 several ways. The alchemists used to keep mercury at a boiling heat 

 for a month, or longer, in a matrass, or a flask with a tolerably long I 

 neck, but having free communication with the air. It thus slowly ' 

 absorbed oxygen, becoming converted into binoxide and was called by 

 them merruriii* prefipitatus per se. It is now however generally pre- 

 pared by calcination from mercuric nitrate when it has a bright orange 

 colour, and is in the state of shining crystalline grains. Sometimes it 

 is precipitated from a solution of a persalt of mercury by caustic 

 potash or soda ; it then differs from the crystalline variety in being 

 converted into oxalate of mercury by the action of oxalic acid. 



Binoxide of mercury darkens in colour when heated, but again 

 becomes red on cooling. When ignited it is resolved into metallic 

 :iy and oxygen gas. Chlorine acts upon it, especially when 

 inoiit, hypochlorous acid and an oxychloride of mercury being formed. 

 Reducing agent* also readily attack it. It is a powerful base forming 

 'lolls of mercuric oxide, or shortly, mercuric salts. 



Mercury and sulphur form two sulphides corresponding to the two 

 oxide* : 



is usually prepared artificially. The Chinese are very successful 

 manufacturers of vermilion : the following is supposed to be the 

 process they adopt. One hundred ' parts of mercury and thirty- 

 eight of sulphur are triturated for two or three hours ; twenty -five 

 parts of solid caustic potash and one hundred and fifty of water are 

 then added, and the whole heated to about 11:) Fahr. for several 

 hours. It must be constantly stirred at first, and, when the desired 

 tint is obtained, removed from the fire and well washed with cold 

 water. 



In this country vermilion is commonly made by triturating mcrcuiy 

 with about one sixth of its weight of sulphur, and then subliming. 

 The beauty of the tint is said to depend upon the amount of levigation 

 to which the sublimate is afterwards subjected. 



Protosulphide of mercury is also thrown down when sulphuretted 

 hydrogen gas is passed through a solution of a mercuric salt. It is 

 black, but may be made to assume a red colour by sublimation. It 

 is insoluble iu aqueous solutions of the alkalies anil in all acids except 

 aqua regia. It is dissolved however in hydrochloric acid when arsenic 

 or antimonic acids and some other oxidising agents are present. 



Mereur/i and iotliite form : 



1. Protoiodide of mercury ..... Hirl 



2. Sesqui-iodidc of mercury . . . . . Hff 2 I 3 



3. Biniodidc of mercury ..... Hgl^ 



1. Protoiodide of mercury. (Hgl). Green, or diaiodide of, m ercuri/. 

 Slercnrous iodide. Prepared by triturating an equivalent of mereury 

 with one of iodine, the mixture being moistened with a little alcohol 

 to keep down the temperature and consequently prevent too rapid 

 action and decomposition. It is also precipitated when a mercurous 

 salt is mixed with solution of iodide of potassium. It is somewhat 

 unstable. 



2. Seff/iii-iodide of mercury (Hg,J 3 ). Kcrmnto*mercune iodide. Pre- 

 cipitated when a solution of iodine in iodide of pofcissium is added to 

 a solution of mercurous nitrate. Alcohol extracts no mercurous iodide 

 from this compound a proof that it is not a mere mixture of mercu- 

 rous and mercuric iodide. 



3. Biniodide of mereitri/ (HgL) Mercuric iodide. Prepared as the 

 protoiodide, two equivalent! of iodine being used, or by precipitation 

 from a mercuric salt by iodide of potassium. It is at first salmon- 

 coloured, but by molecular alteration speedily becomes a magnifi- 

 cent scarlet. It sublimes in yellow-tabular crystals, but on rubbing, 

 scratching, or merely agitating, undergoes the alteration just mentioned 

 and becomes scarlet ; in short, biniodide of mercury is, in crystallo- 

 graphic language, dimorphous. During the change heat is evolved. 



Double saltx of biniodide of mercury with other compounds of 

 mercury and with the alkaline iodides may be easily formed. 



Mercury and bromine form compounds very much resembling the 

 iodides. 



Mereury and chlorine form two important chlorides : 



1 . Protocliloride of mercury 



2. Bichloride of mercury 



. HgCl 

 . IlgCU 



1. Protosulphide of mercury 



2. Bisulphide of mercury 



HgS 

 HgS, 



1. Protoiulphide of mercury (HgS). Mercurous sulphide. Ethiop's 

 mineral. This compound is precipitated when sulphuretted hydrogen 

 U passed through a solution of a mercurous salt. It is also frequently 

 made by triturating two hundred parta of mercury with sixteen of 

 sulphur. It is almost as unstable as the protoxide. 



2. liirulpliidf of mercury (HgS,). Mercuric sulphide. Cinnabar. 

 Vermilion. This U the most common ore of mercury. [MERCURY, in 

 NAT. HIST. Div.] It is largely used as a pigment, but for this purpose 



ARTS ASD SCI. DIV. VOL. V. 



1. Protoehloride of mercury (HgCl). StAtUoriek or diehloride of 

 mercury. Mtrcurous chloride. Calomel, This compound of mercury 

 has been known for nearly three centuries. It was first called mtomel 

 (from na\bs,gnoil, and /it'Aar, black) by Sir Theodore Tnrquetde Mayenne, 

 though for what reason is not satisfactorily known. It occurs native 

 [MKKCURY, in NAT. HIST. Div.] but for use in medicine is always 

 prepared artificially. This is sometimes accomplished by adding 

 chloride of sodium to a solution of a mercurous salt, and well washing 

 and drying the precipitate. More usually, however, it is obtained by 

 submitting to the action of heat a mixture, in equivalent proportions, 

 of chloride of sodium and protosulphate of mercury ; double decom- 

 position takes place, protochloride of mercury sublimes and sulphate 

 of soda remains. If the vessel in which this operation is conducted be 

 small, the calomel condenses in brilliant quadrilateral prisms termi- 

 nated by four-sided pyramids ; but if the receiver be capacious, and 

 especially if it be filled with steam, the calomel condenses in the form 

 of an exceedingly fine white or slightly buff-tinted powder. By the 



latter modification of manufacture the trouble of grinding is avoided. 

 Calomel is tasteless and insoluble iu water. The fixed alkalies con- 

 vert it into protoxide. Ammonia changes it to blitch precipitate or 

 mercurous amidochloride. (HgCl-fHgNH 2 ). It is very soluble in strong 

 solutions of alkaline salts, but much less so in dilute solutions ; decom- 

 position into metallic mercury and mercuric salt accompanies the 

 solution. 



2. Bichloride of mereury (HgCl a ). Percldoride of mercury. Mer- 

 curic chloride. Corrosive sublimate. This compound may be formed 

 by the direct union of its constituents, but is usually prepared by 

 submitting to an elevated temperature a mixture, in equivalent pro- 

 portions, of bisulphate of mercury and chloride of sodium. The 

 following equation exhibits the reaction : 



HgO,, 28O,+ 2NaCl = HgCl, + 5(NaO, SO,). 



Corrosive sublimate crystallises in white needles or in a semi-vitreous 

 mass. It has an acrid, peculiarly metallic taste that is very unpleasant. 

 It is soluble in three parts of boiling, and eighteen to twenty of cold 

 water. Hot alcohol dissolves its own weight of this salt, and cold 

 alcohol one-third of its weight ; ether also readily dissolves it : indeed, 



p p 



