TOOLS AND SUPPLIES; FUNDAMENTAL PROCESSES 235 



extent, upon the class of metals to be joined by it. Soft 

 solder, sometimes called white or tin solder, is made of soft, 

 readily fused metals or alloys. Such metals as tin, lead-tin 

 and alloys of tin, lead and bismuth are usually used. A 

 good formula for the composition of soft solder is: Lead, 

 207 parts; tin, 118 parts. To weaken the solder increase the 

 number of parts of tin. Increasing the number of parts of 

 lead will strengthen the solder. The solder may be prepared 

 in a graphite crucible at a low temperature by mixing with 

 an iron rod and then running into iron molds. 



207. Soldering Fluxes are substances used to remove 

 the oxide which forms on the surface of a metal. They are 

 melted and run on the metal where the soldered joint is to I e 

 formed. The fluxes generally used are powdered rosin or a 

 solution of chloride of zinc, used alone or combined with s;.l 

 ammoniac. 



A soldering fluid is a liquid flux and may be prepared 

 by mixing 27 parts neutral zinc chloride, 11 parts sal 

 ammoniac, and 62 parts of water; or 1 part sugar of milk, 

 1 part glycerine and 8 parts of water. 



A very common liquid is prepared by dissolving in an 

 earthenware vessel small pieces of scrap zinc in commercial 

 muriatic acid. Dissolve one piece at a time to prevent too 

 rapid generation of heat, which might break the jar. Finally 

 secure a saturated solution by adding more zinc than will 

 dissolve. For use in soldering, the solution should be diluted 

 with the addition of its own bulk of water, mixed and filtered. 

 The addition of a few drops of liquid ammonia will increase 

 the activity of the flux, which should be kept in a wide- 

 mouthed bottle and applied to the joint to be soldered, just 



