410 



LEAD. 



oilier, so as In make it water tiulit, without soldering. 

 1 lii< is a very great advantage ; since, when pieces 

 ..lerrd tuaether, the expansion and contraction, 

 by a change of temperature, soon cause a rupture. 

 Although it is in very general use for water cisterns, 

 pumps, uiul pipes for conveying water, serious objec- 

 tions have, from time to time, been urged against its 

 employment for this purpose. Doctor Christison has 

 found tliat, in pure water, it is oxidized with con- 

 siderable rapidity, carbonate of lead being formed by 

 the action of the oxygen and carbonic acid of the 

 air. But if the water, as is the case with the majo- 

 rity of springs, contains a small proportion of saline 

 matter, especially if a sulphate be present, which 

 never fails to precipitate lead from any of its solu- 

 tions, the liability of the water to be prejudiced by 

 the lead is very small. And in other cases, there 

 fan be no danger in delivering water through aque- 

 ducts of lead, provided they are constantly Sept full 

 of water, so as always to exclude the air. Great 

 mischief has been produced by the use of lead in 

 dairies. If the milk runs into the slightest acidity, 

 some lead will be dissolved, and injurious conse- 

 quences will follow if it is taken into the stomach. 

 In the granulation of lead for shot, a small portion 

 of arsenic is added. The proportion is about two 

 per cent, of the white or yellow arsenic. The com- 

 pound is heated red-hot for three hours in an iron 

 pot, protected by a tight cover, when the contents 

 are let fall into a reservoir of water, from a height of 

 ten to 150 feet, as the shot are to be coarser or 

 finer. One part of tin and two of lead form an 

 alloy fusible at 350 Fahr., which is used by tinmen 

 under the name of soft solder. Lead also forms an 

 imperfect alloy with copper. The metal used for 

 common brass-cocks is an alloy of these two metals. 

 The union of these two metals, however, is exceed- 

 ingly slight ; for, upon exposing the alloy to a heat 

 no greater than tliat in which lead melts, the lead 

 almost entirely runs off of itself. This process is 

 called eliquation. Of the oxides, the mixture of the 

 protoxide and deutoxide, which forms the red-lead, 

 is of considerable importance as a pigment. Its 

 manufacture in Germany is conducted as follows: 

 180 pounds of lead are calcined for eight hours upon 

 the hearth of a cupola furnace, and, being constantly 

 stirred, it is then left in the furnace for sixteen 

 hours, and only stirred at intervals. This calcined 

 lead, or massicot, is ground in a mill with water, 

 washed on tables, and, being dried, is put into stone 

 pots, of such a size, that thirty-two pounds fill them 

 somewhat more than one quarter full. Several of 

 these pots are laid horizontally in the colour furnace, 

 so that the flame may go quite round them, and a 

 piece of brick is put before the opening of each pot. 

 A fire is kept up in this furnace for about forty-eight 

 hours, and the matter in the pots stirred every half 

 hour. The process being over, the red-lead is passed 

 through a sieve. In this operation, 100 pounds of 

 lead generally increase ten pounds in weight. Red- 

 lead is also made from litharge, by heating it in pots 

 in a reverberatory furnace. TJie salts of lead have 

 the protoxide, as has before been remarked, for their 

 base, and are readily distinguished by the following 

 general characters : 1. The salts which dissolve in 

 water usually give colourless solutions, which have 

 an astringent, sweetish taste ; 2. placed on charcoal, 

 they all yield, by the blow-pipe, a button of lead,; 

 3. ferroprussiate of potash occasions in their solu- 

 tions a white precipitate ; 4. sulphureted hydrogen 

 and hydrosulphurets produce a black precipitate ; 

 5. a plate of zinc a white precipitate, or metallic 

 leaf. Most of the acids attack lead. The sulphuric 

 <loes not act upon it, unless it be concentrated and 

 boiling. Sulphurous acid gas escapes during this 



process, and the acid is decomposed. U'heii the dis- 

 tillation is carried on to dryness, a saline white mass 

 is produced, a small portion of which is soluble in 

 water, and is the sulphate of lead; it affords crystals. 

 The residue of the while mass is an insoluble sul- 

 phate of lead. It consists of 5 acid and 14 prot- 

 oxide of lead. Nitric acid acts strongly on lead. 

 The nitrate solution yields by evaporation tetrahedral 

 crystals, which are white, opaque, and of a specific 

 gravity of 4. They consist of 6-75 acid, and 14 

 protoxide. A subnitrate may be formed by boiling 

 in water equal weights of the nitrate and protoxide; 

 also by boiling a solution of 10 parts of the nitrate 

 on 7 - 8 of metallic lead. Acetic acid dissolves lead 

 and its oxides ; though probably the access of air 

 may be necessary to the solution of the metal itself 

 by this acid. fVhite lead, or ceruse (see Ceruse), is 

 made by rolling leaden plates spirally up, so as to 

 leave the space of about an inch betweeen each coil, 

 and placing them vertically in earthen pots, at the 

 bottom of which is some good vinegar. The pots 

 are covered, and exposed for a length of time to a 

 gentle heat in a sand-bath, or by bedding them in 

 dung. The vapour of the vinegar, assisted by the 

 tendency of the lead to combine with the oxygen 

 which is present, corrodes the lead, and converts the 

 external portion into a white substance, which comes 

 off in flakes when the lead is uncoiled. The plates 

 are thus treated repeatedly, until they are corroded 

 through. Ceruse is the only white used in oil 

 paintings. Commonly, it is adulterated with a mix- 

 ture of chalk in the shops. It may be dissolved 

 without difficulty in the acetic acid, and affords a 

 crystallizable salt, called sugar of lead, from its 

 sweet taste. This, like all the preparations of lead, 

 is a deadly poison. The common sugar of lead is an 

 acetate ; and Goulard's extract, made by boiling 

 litharge in vinegar, a subacctate. The power of this 

 salt, as a coagulator of mucus, is superior to tliat of 

 the other. If a plate of zinc be suspended, by a 

 thread, in a solution of acetate of lead, the lead will 

 be revived, and form an arbor Saturni. The acetate, 

 or sugar of lead, is usually crystallized in needles, 

 which have a silky appearance. They are flat, four- 

 sided prisms, with dihedral summits ; specific gra- 

 vity, 2-345. It is soluble in 5 times its weight of 

 cold water, and in somewliat less of boiling water. 

 Its constituents are 20-96 acid, 58-71 base, and 14-32 

 water. Acetate and subacetate of lead hi solution have 

 been used as external applications to inflamed surfaces, 

 scrofulous tores, and as eyewashes. In some extreme 

 cases of hemorrhage from the lungs and bowels, the 

 former salt has been prescribed, but rarely, and in 

 minute doses, as a corrugant or astringent. The 

 colic of the painters shows the very deleterious 

 operation of this metal when introduced into the 

 system in the minutest quantities at a time. A course 

 of sulphureted hydrogen waters, laxatives, of which 

 sulphur, castor-oil, Epsom salts, or calomel, should 

 be preferred, a mercurial course, the hot sea bath, 

 and electricity, are the appropriate remedies. Dealers 

 in wines have occasionally sweetened their acid wiues 

 with litharge, or its salts. This nefarious adultera- 

 tion is at once detected by the use of snlphureted 

 hydrogen water, which will throw down the lead in 

 the state of a dark brown sulphuret. Burgundy 

 wine, and all such as contain tartar, will not hold 

 lead in solution, in consequence of the insolubility of 

 the tartrate. The proper counter-poison for a dan- 

 gerous dose of sugar of lead is solution of Epsom or 

 Glauber salt, liberally swallowed; either of which 

 medicines instantly converts the poisonous acetate ot 

 lead into the inert sulphate. Sugar has been found 

 to neutralize the poisonous action of acetate of lead, 

 and therefore is an excellent antidote to it. 



