142 Van Name — 



Estimation of Copper 



as Sulphocyanide 











Table II. 

















Final volume 200 cm3 . 















HC1 



















sp. gr. 



Tar- 



NH 4 SCN 



Cu 2 S 2 



Calcu- 







Cu 





about 



taric HNH 4 S0 3 



approx. 



(CN) 2 



lated 







taken. 



Bi. 



1-17. 



acid. sat. sol. 



to/ 10. 



found. 



asCu. 



Error. 





grm. 



grm. 



cm 3 . 



grm. cm 3 . 



cm 3 . 



grm. 



grm. 



grm. 



1. 



•0793 



0*2 



6 



1 2 



15 



•1329 



•0695 



— •0098 



2. 



a 



0-2 



it 



a a 



35 



•1479 



•0773 



— •0020 



3. 



n 



0-2 



a 



If it 



60 



•1504 



•0786 



—•0007 



4. 



u 



o-i 



a 



it a 



100 



•1512 



•0790 



— •0003 



5. 



a 



0-3 



is 



« a 



125 



•1515 



•0792 



— •0001 



6. 



a 



0-2 



(S 



a a 



a 



•1518 



•0793 



•oooo 



7. 



a 



0*2 



it 



u tc 



a 



•1519 



•0794 



+ •0001 



8.* 



a 



0-2 



Sn 



a 



u a 



230 



•1519 



•0794 



+ •0001 





taken as 

















SnCl 4 + HCl. 

















grm. 















9. 



u 



0-2 



5 



a a 



40 



•1502 



•0785 



— •0008 



10. 



u 



0'2 



6 



(i it 



125 



•1514 



•0791 



—•0002 



11. 



« 



0*2 



5 



• it a 



130 



•1516 



•0792 



— •0001 





taken as 













• 





SnCl 2 + HCl. 

















grm. 















12. 



tt 



0-2 



As. 

 grm. 



6 



a a 



125 



•1529 



•0799 



+ •0006 



13. 



c< 



0-2 



Sb. 

 grm. 



a 



a a 



n 



•1523 



•0796 



+ -0003 



14. 



a 



As, 



0-2 



Bi, Sb, 



of each 



grm. 



a 



Sn 



2 " 



u 



•1518 



•0793 



•oooo 



15. 



•0795 



o-i 



a 



u tt 



130 



•1523 



•0796 



+ •0001 



16. 



a 



o-i 



tc 



u a 



a 



•1525 



•0797 



+ •0002 



stannous condition requires some care, because the bisulphite is 

 often acted upon by a solution of stannous chloride, and a 

 slight precipitate of sulphur thrown down from a mixture of 

 these solutions upon standing. Unless, however, the amount 

 of tin present is more than equivalent to the copper, it may be 

 readily oxidized to the stannic state by merely adding the sul- 

 phocyanide before the bisulphite. The tin then acts as the 

 reducing agent and a corresponding amount of copper is thrown 

 down, after which bisulphite may safely be added and the rest 



* Final volume 300 cm3 . 



