266 BELL SYSTEM TECHNICAL JOURNAL 



and an arsenic-modified solder which have undergone similar handling 

 and cooling treatments. The arsenic-bearing solder exhibits a finer 

 and more uniform texture. The finer texture is associated with im- 

 proved handling characteristics and freedom from porosity in the 

 finished joint. The texture of the solder is more buttery in the wiping 

 process and there is less tendency for the lower freezing constituents to 

 drain from the partially finished joints than with the lead-tin composi- 

 tions. Practically, this provides for the splicer a longer forming range, 

 although the solidification range is materially the same as for the 

 corresponding unmodified alloy. 



Although the mechanism by which arsenic reduces the size of the 

 dendrites and refines the grain of wiping solder has not been definitely 

 established, it seems probable that it either provides new and more 

 numerous nuclei of crystallization around which the primary lead 

 precipitates, or imposes barriers against the growth of the primary 

 lead crystals or both. Arsenic forms a compound, Sn3As2, with tin 

 and it is probable that this constituent is responsible for the mechanism 

 postulated. In slowly cooled solders this compound is discernible 

 beginning at approximately 0.1 per cent arsenic. With a greater 

 number of precipitated crystals present a greater surface is made 

 available to which the molten eutectic may cling, producing a readily 

 formable mass. 



Laboratory observations on the solder have been verified by field 

 tests in the Bell System. The arsenic-bearing solder is handled in the 

 same way as the ordinary lead-tin compositions. Joints have been 

 wiped on large and small aerial and underground cables and in difficult 

 situations involving large branched joints. The consensus of splicers 

 from several different localities is that the solder possesses handling 

 properties superior to those of the lead-tin compositions. These joints 

 in all cases were pressure tested after wiping and found to be sound. 



Regarding the possible health hazard involved in using the new 

 solder, tests have been made to determine whether arsenic or arsenic 

 compounds would be volatilized from this alloy under the conditions 

 encountered in practice. These tests gave entirely negative results 

 and showed that no additional hazards would be introduced by 

 substituting arsenic-bearing solder for standard solder. 



