ALLOYS 01' LEAD. 59/> 



the elements of 1 atom of acetic acid, in the form of carbonic 

 acid and acetone, (Matteucci, Wohler). This basic salt is very 

 soluble, and crystallizes in plates of a pearly lustre. 



A sexbasic acetate of lead, 6PbO, (C 4 H 3 O 3 ), is formed on 

 dropping a solution of the neutral, or of tribasic acetate of lead, 

 into ammonia in excess. It is a white precipitate, which ex- 

 amined by the microscope, has a crystalline aspect. It con- 

 tains a little water, which it loses when dried in vacuo. 



Alloys of lead. Lead and tin may be fused together in all 

 proportions. M. Rudberg finds that these metals combine in 

 certain definite proportions having fixed points of congela- 

 tion : 



ALLOYS OF LEAD AND TIN. 



1 atom of lead and 3 atoms of tin, congeal at 68.6. 



1 atom of lead and 1 atom of tin, at 464. 



2 atoms of lead and 1 atom of tin, at 518. 



3 atoms of lead and L atom of tin, at 536. 



A thermometer placed in a fluid alloy of 1 atom of lead and 

 2 atoms of tin, becomes stationary when the temperature falls 

 to 392, a portion solidifies, and a more fusible alloy separates ; 

 the temperature again falls, and afterwards becomes stationary 

 at 368.6, the crystallizing point of the alloy composed of I 

 atom of lead, and 3 atoms of tin. If the alloy contains so much 

 tin that its point of complete congelation is under 368.6, the 

 last compound always separates from it, at that point, and the 

 thermometer remains stationary for a time, whatever may be 

 the proportion of the metals in the alloy.* Fine solder is an 

 alloy of 2 parts of tin and 1 of lead ; it fuses at about 360, and 

 is much employed in tinning copper. Coarse solder contains 

 one fourth of tin, and fuses about 500 ; it is the substance em- 

 ployed for soldering by plumbers. 



Lead, as reduced from the native sulphuret, always contains a 

 little silver. The latter is separated by allowing two or three 

 tons of the melted metal to cool slowly in a hemispherical iron 

 pot; when the lead, as it solidifies, separates in crystals, which 

 can be raked out. The silver remains almost wholly in the 

 more fusible portion, or what may be looked upon as the 

 mother-liquor of these crystals ; so that by this operation the 

 argentiferous alloy is greatly concentrated. This mode of 



* Rudberg, An. de China, et de Phys. t. 48, p. 363. 



