LEA 



LEA 



Oils dissolve the oxides of lead, and be- 

 come thick and consistent ; in which 

 slate they are used as the basis of 

 plasters, cements for water-works, paints, 

 Sec. 



In the dry way, lead alone is oxided 

 and vitrified. When fused with fixed 

 alkaline salts, it is converted into a dark 

 coloured scoria, partly soluble in water. 

 The neutral salts in general are not act- 

 ed upon by lead. Nitre oxides this me- 

 tal when heated with it, though scarcely 

 any commotion or apparent flame is pro- 

 duced by its action. Sulphur readily 

 dissolves it in the dry way, and pro- 

 duces a brittle compound, of a deep grey 

 colour and brilliant appearance, which 

 is much less fusible than lead itself; a 

 property which is common to all the 

 combinations of sulphur with the more 

 fusible metals. 



The phosphoric acid, exposed to heat 

 together with charcoal and lead, be- 

 comes converted into phosphorus, which 

 combines with the metal. This combina- 

 tion does not greatly differ in appearance 

 from ordinary lead : it is malleable, and 

 easily cut with a knife ; but it loses its 

 brilliancy more speedily than pure lead ; 

 and, when fused upon charcoal with the 

 blow-pipe, the phosphorus burns, and 

 leaves the lead behind. 



Lead decomposes sal ammoniac, or mu- 

 riate of ammonia, by the assistance of 

 heat : its oxides unite with the muriatic 

 acid of that salt in the cold, and disen- 

 gage its volatile alkali. When the vola- 

 tile alkali is obtained by distilling sal am- 

 moniac with the oxides of lead, the resi- 

 due consists of the muriate of lead. 



Litharge fused with common salt de- 

 composes it ; the lead unites with mu- 

 riatic acid, and forms a yellow compound, 

 at present used in this country as a pig- 

 ment. The alkali either floats at top, or 

 is volatilized by the heat, if strongly urg- 

 ed. The same decomposition takes place 

 in the humid way, if common salt be ma- 

 cerated with litharge, and the solution 

 will contain the p'ure alkali. 



Lead unites with most of the metals. 

 Gold and silver are dissolved by it in a 

 slight red heat. Both these metals are 

 said to be rendered brittle by a small ad- 

 mixture of lead, though lead itself is ren- 

 dered more ductile by a small quantity of 

 them. Platina forms a brittle compound 

 with lead ; mercury amalgamates with it ; 

 but the lead is separated from the mercu- 

 ry by agitation, in the form of an impalpa- 

 ble black powder, if oxygen be present, 

 which is at the same time absorbed. 

 Copper and lead do not unite but with a 



strong heat. If lead be heated so as to 

 boil and smoke, it soon dissolves pieces 

 of copper thrown into it : the mixture 

 when cold is brittle. The union ofthe.se 

 two metals is remarkably slight; for, 

 upon exposing the mass to a heat no 

 greater than that in which lead melts, 

 the lead almost entirely runs off by it- 

 self. This process, which is peculiar to 

 lead with copper, is called eliquation. 

 The coarser sorts of lead, which owe 

 their brittleness and granulated texture 

 to an admixture of copper, throw it up 

 to the surface on being melted to a small 

 heat. Iron does not unite with lead, as. 

 long as both substances retain their me- 

 tallic form. Tin unites very easily with 

 this metal, and forms a compound which 

 is much more fusible than lead by itself, 

 and is for that reason used as a solder for 

 lead. Two parts of lead and one of tin, 

 form an alloy more fusible than either 

 metal alone; this is the solder of the 

 plumbers. Bismuth combines readily 

 with lead, and affords a metal of a fine 

 close grain, but very brittle. A mixture 

 of eight parts bismuth, five lead, and 

 three tin, will melt in a heat which is not 

 sufficient to cause water to boil. Antimo- 

 ny forms a brittle alloy with lead. Nickel, 

 cobalt, manganese, and zinc, do not unite 

 with lead by fusion. 



It will appear, from the foregoing ob- 

 servations, that the uses of lead are very- 

 extensive. It is easily reduced to thin 

 sheets, adapted to the covering of build- 

 ings ; to be formed into pipes of all 

 sizes, and fitted for divers purposes. Its 

 oxides are used as paints ; in the manu- 

 facture of glass; and in the glazing of 

 earthen- ware, &c. 



LEAD, black. See the article luox. 



LEAD, sugar of. A salt, denominated 

 from its composition, by modern che- 

 mists, acetite of lead, is much used in 

 calico-printing, and other manufactures. 



LEAGUE, a measure of length, con- 

 taining more or less geometrical paces, 

 according to the different usages and 

 customs of countries. A leagnie at sea, 

 where it is chiefly used by us, being a 

 land measure mostly peculiar to the 

 French and Germans, contains 3,000 geo- 

 metrical paces, or three English miles. 

 The French league sometimes contains 

 the same measure, and in some parts of 

 France it consists of 3,500 paces .- the 

 mean or common league consists of 

 2,400 paces, and the little league of 

 2,000. The Spanish leagues are larger 

 than the French, seventeen Spanish 

 leagues making a degree, or twenty 

 French leagues, or sixty -nine and an half 



