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BELL SYSTEM TECHNICAL JOURNAL 



6. The health hazard under normal conditions of use should be 

 negligible. 



An investigation was made of modifications of the lead-tin type 

 wiping solder to produce a solder which more fully meets the practical 

 requirements than does the present compositions. Through the addi- 

 tion of 0.1 per cent of arsenic substantial improvements have been 



Fig. 1 — Photomacrograph of a nominal 38% tin-62% lead wiping solder. The 

 sample was slowly cooled from 300° C. Specimen etched with a mixture of 4 parts 

 of glacial acetic acid and 1 part of 30% hydrogen peroxide. 



achieved in certain of the characteristics. The nominal composition 

 of an alloy which shows this improvement is tin — 37.25 per cent, 

 arsenic — 0.1 per cent, and balance lead. The effect of arsenic mani- 

 fests itself at percentages as low as 0.04 per cent. Amounts much 

 over 0.1 per cent should be avoided because of a tendency to segrega- 

 tion at the higher percentages. As the tin is reduced below the recom- 



