MEKCDET.] 



CHEMISTRY. 



375 



also he obtained by heating the nitrate. The sulphate is 

 readily produced by boiling mercury with concentrated 

 sulphuric acid ; during which process large quantities of 

 sulphurous acid, in a gaseous state, are evolved. Nitric 

 acid dissolves mercury, by which the proto-nitrate is pro- 

 duccd. On diluting the concentrated solution, a sub- 

 nitrate falls down in the form of a white precipitate. 

 The solution of the nitrate is often sold by unprincipled 

 persons in the streets of our large towns, as a polishing 

 liquid. If applied to a silver or copper surface, it at 

 once produces a brilliant polish ; but penetrating into 

 the pores of those metals, and forming an amalgam, 

 their tenacity is at once destroyed, and the article ren- 

 dered useless. 



The chlorides of mercury are of great importance as 

 forming two well-known substances used in medicine. 

 The sub-chloride is the well-known calomel. It is a 

 white substance, and, when closely examined, has a 

 crystalline structure. It may be produced by adding a 

 solution of common salt to one of the sub-nitrate of 

 mercury, or by rubbing together, in a mortar, metallic 

 mercury, common salt, and corrosive sublimate. The 

 product is then sublimed, and the sub-chloride, or 

 calomel, is so obtained in a pure form. It is but 

 sparingly soluble in water, and may be so distinguished 

 from the other chloride. Corrosive sublimate is well 

 known as a deadly poison to animals. In minute quan- 

 tities, it is, however, employed in medicine ; and both it 

 and the sub-chloride have the property of producing a 

 great flow of saliva, and for this purpose even moderate 

 doses are sufficient. Corrosive sublimate is used as a 

 preservative agent for both animal and vegetable sub- 

 stances. It may be prepared by burning mercury in a 

 jar of chlorine gas, or by subliming common salt and 

 the sulphate of mercury together. We may here re- 

 mark, that in case of accidental poisoning, or of suicide, 

 the best antidote hich can be administered is the white 

 of ggs, which, by coagulation with the salt, prevents 

 any action on the intestines. 



There are two iodides of mercury. The sub-iodide is 

 a yellow powder, which may easily be procured by 

 adding a little iodide of potassium in solution, to one of 

 corrosive sublimate ; if more iodide be added, then a 

 red powder is produced, which is the proto-iodide: if, 

 however, too much of the iodide solution be employed, 

 the iodide of mercury will be dissolved, and the liquid 

 will become transparent. We have frequently produci-d 

 both iodides by placing iodine in powder on metallic 

 mercury, and inserting the poles of a powerful voltaic bat- 

 tery in the metal : one is then to be withdrawn, so as to 

 produce the disruptive discharge. A combination of 

 the metal and the iodine will then take place, and the 

 two iodides are produced. In many chemical works 

 these iodides are respectively termed the proto, and 

 biniodide. It has been proposed to use these substances 

 as pigments ; but they are liable to decomposition, and 

 so defeat that purpose. 



There are two sulphides of mercury. One, the sub- 

 sulphide, is readily produced by passing sulphuretted 

 hydrogen tras through a solution of the sub nitrate, by 

 which a bkv-k powder is produced. The sulphide proper 

 is well known in the substances termed cinnabar and 

 vermilion ; the latter of which has a beautiful red colour, 

 and is much employed as a pigment. Cinnabar is a 

 common ore of the metal. The sulphide, produced by 

 passing sulphuretted hydrogen through the nitrate of 

 mercury, is of a deep black colour ; but on being heaceu, 

 it becomes reddish brown ; and the substance, if heated 

 with a solution of sulphide of potassium, produces the 

 pigment vermilion. 



Mercury forms a compound with cyanogen as the 

 cyanide of the metal, which isthe usual source of cyanogen 

 for experimental purposes. The cyanide may be pro- 

 cured by boiling a 'solution of prussiate of potash with 

 sulphate of mercury, and subsequently evaporating the 

 clear solution, when crystals of the white cyanide will be 

 obtained. 



One of the most interesting and useful compound < of 

 the metal is that termed fulminating mercu.y, which is 



extensively employed in the manufacture of percussion- 

 caps ; an invention which has ^completely changed the 

 construction of muskets, fowling-pieces, (fee., and has 

 made them infinitely more serviceable for the purpose 

 they are intended for. In the old form of such guns, the 

 powder was ignited by means of a flint and steel placed 

 over the barrel, and the fracture of the ilint rendered the 

 musket useless. It was necessary to pour a little powder 

 into the pan, which communicated, by means of a small 

 hole, with the charge in the interior of the barrel ; and it 

 frequently happened that a gust of wind or a shower of rain 

 rendered it impossible to ignite the charge. By means of 

 the percussion-cap, the "nipple" is kept qiu'te covered 

 and protected, and, at the instant the hammer is allowed 

 to fall, the powder in the cap explodes, and the charge is 

 inflamed. The following method is that usually adopted 

 in manufacturing the fulminating mercury, which is a 

 combination of fulminic acid with the metal. Into a tall 

 glass or porcelain vessel introduce one ounce of mercury, 

 and on this pour gradually four ounces, by measure, of 

 nitric acid, of a specific gravity of 1 '45 to I '50. Con- 

 siderable heat will be evolved during the solution of the 

 metal ; and when all is dissolved, and the mixture still 

 hot, it must be poured into six ounces of strong alcohol. 

 As the mixture instantly froths up to a great degree, and 

 abundance of vapour is given off, this should be done in 

 a vessel of considerable height and capacity, to prevent 

 the loss of its contents. A powder will soon be produced, 

 which is the fulminate. This may be allowed to settle, 

 and as much as possible of the clear liquid is then to be 

 poured away. The vessel is to be tilled up with cold 

 water, and the contents are then to be gradually poured 

 on to filtering-paper, on which the powder will be re- 

 tained. This is to be well washed with cold water until 

 all trace of acid is removed. The powder itself should 

 always be kept wetted until required for use, as, if dry, 

 the slightest friction would cause it to explode violently. 

 It is best to remove the filtering-paper whilst wet, and to 

 place it in a dish kept full of water; and when any 

 portion of the fulminate is wanted, such should be re- 

 moved in as small a quantity as possible, by means of a 

 paper scoop, and allowed to dry by evaporation in the open 

 air. We cannot too strongly caution our readers in respect 

 to the manufacture of this dangerous compound. The 

 quantities we have given are such as would be employed 

 for making it on a large scale ; but if the student desire to 

 acquaint himself with the properties of fulminating ner- 

 cury, he should use but a few grains of the metal, and 

 the acid and alcohol in the relative proportions already 

 indicated. To impress the necessity of caution, we may 

 observe, that a few years ago, an able and experienced 

 chemist, employed in manufacturing the article at the 

 Apothecaries' Hall, London, was shattered to pieces, and 

 the fragments of his body blown to an astonishing dis- 

 tance, by an explosion of but a moderate quantity of this 

 dangerous substance. The tyro in chemical science 

 should never attempt to make it at all. We have 

 already named the fulminates of gold and silver, 

 which are producible by a similar process to that jnst 

 described. 



Some of the salts of mercury are extensively used for 

 the purpose of amalgamating the zinc plates of voltaic 

 batteries ; and for this purpose the nitrate is the most 

 convenient. The same end is also obtained by brushing 

 metallic mercury over the zinc, the latter being immersed 

 in dilute sulphuric acid. 



The detection of mercury, in a combined state, is 

 generally very easy. The sulphate, nitrate, <fec. , readily 

 part with the metal, if they are moistened with water, 

 and placed on a sheet 9f zinc. A gold or copper wire is 

 then made to touch the metal, the wire being passed 

 through the moistened salt. The latter is at once decom- 

 posed ; and metallic mercury, if present, will turn tha 

 end of the wire to a white colour. If a gold wire be 

 employed, the mercury is at once removed by the heat of 

 a spirit-lamp. Mercury has a peculiar effect ou the 

 human system ; and persons employed in the mines, or 

 in working with the metal, are generally afflicted with 

 paralysis. 



