SHEET METALS 447 



Lead sheets are used by the plumber for roofing, for making 

 pipes, cisterns, tanks, leaden coffins, and for many other 

 purposes. The ease with which lead can be worked causes 

 it to be employed in all countries which have arrived at any 

 degree of civilization. The Chinese use large quantities 

 for making the thin sheets in which they pack their tea. 

 Their process for making these sheets is simple and ingenious. 

 One workman sits on the floor with one large flat stone before 

 him and another at his side. A second workman stands by 

 with a pot of melted lead, part of which he pours on the stone. 

 The first workman places the movable stone on the melted 

 metal and compresses it into a flat thin sheet which is after- 

 wards trimmed. .The process is expeditious and effectual. 



Lead boils at white heat, absorbs oxygen from the air, 

 and passes into lead oxide (PbO). Lead is little acted upon 

 by muriatic acid, but is readily dissolved by nitric acid. 



519. Alloys of Lead. Oftentimes it is necessary to use 

 an alloy which will expand on cooling. Such an alloy is 

 obtained by melting together 9 Ibs. of lead, 2 Ibs. of anti- 

 mony, and 1 Ib. of bismuth. The alloy is used to fasten bolts 

 firmly into foundation stones. The process is as follows: 

 After the bolt hole is drilled in the stone a couple of short, 

 small holes are drilled at an angle to the big hole. As the 

 rnetal is poured in, it flows around the bolt and also into 

 these small holes. On cooling, the metal expands and for 

 this reason it is almost impossible for the bolt to pull out. 

 When drilling holes in stone, water is always used and care 

 must be taken to see that the holes are dried out by the use of 

 red-hot iron rods before the melted metal is poured in. If 

 this precaution is not taken, the metal will blow out, and 

 may burn the hands and face of the man who is pouring it in. 



