50 



J. T. Norton, Jr.—Titration of Mercury 









Table I. 















Volume 



HgCl a 









HgCl 2 taken 



Na 2 S a 3 



at 



found 









calc'd as Hg. 



in excess. 



beginning. 



calc'd as Hg. Error. 





grams. 



cm 3 . 



cm 3 . 



grams. 



grams. 





1. 0-0446 



46-28 



200 



0-0343 



0-0103 — 





2. 0-0354 



46-28 



400 



0-0326 



o-oo 



28- 





3. 0-0356 



44-97 



400 



00225 



0-0131- 





4. 0-0345 



44-5 



100 



0-0308 



o-oo 



37 — 





5. 0354 



44-43 



50 



0-0326 



o-oo 



28 — 





6. 0-0382 



22-59 



50 



0-0354 



0-0028 — 





7. 0-0375 



8-58 



50 



0-0385 



0*0010 + 





8. 0-0371 



1-84 



50 



0-0304 



0-0067 — 





9. 0-0731 



2-28 



50 



0-0774 



0-0043 + 





10. 0-1486 



9-34 



50 



0-1489 



0-0003 + 









Table II. 











HgCl 2 Volume 















taken at 



Tem- 



Stand- 



Na 2 S 2 O s 



HgCl 2 







as Hg. beginnin 



y. perature. ing 



in excess. 



as Hg. 



Error. 





grams. cm 3 . 



C. 



minutes. 



cm 3 . 



found. 



grams. 



1. 



0-0738 50 



36° 



40 



16-68 



0-0494 



0-0244 — 



2. 



0-0741 50 



70 



15 



15-42 



0-0738 



0-0003 — 



3. 



0-0741 75 



70 



12 



16-07 



0-0733 



0-0008 — 



4. 



0-0744 50 



70 



10 



146 



0-0755 



0-0011 + 



5. 



0764 50 



72 



7 



6-77 



0-0771 



0-0007 + 



6. 



0-0762 50 



75 



10 



8-54 



0-0799 



0-0037 + 



7. 



0-0756 50 



73 



15 



9-99 



0-0815 



0-0059 + 



8. 



0-0774 50 



68 



15 



10-84 



0-0767 



0-0007 — 



9. 



0-0745 75 



69 



H 



1 



6-62 



0-0805 



0-0060 + 



10. 



0-0736 50 



68 



5 



15-82 



0-0714 



0-0022 — 



These results, although better than those of Table I, are still 

 very uncertain. On the supposition that the change from 

 white to black, which takes place in the solution after the addi- 

 tion of an excess of sodium thiosulphate more or less quickly 

 according to the temperature, was due to an increased amount 

 of HgS in the compound 2HgS.HgCl„, the next step was to 

 ascertain whether this could be avoided by stopping the addi- 

 tion of the thiosulphate at the first indication of a change of 

 color in the white precipitate, diluting the solution with a large 

 amount of cold water and immediately throwing it on the 

 filter. The following table (III) shows the result of the experi- 

 ments. 



In the case of quantities of mercuric chloride up to 0*1 

 gram the results shown in Table III are very satisfactory, but 

 when larger amounts of mercuric chloride are used the errors 

 again become prominent. In Table IY, the effect of lowering 

 the temperature to 60° C. and of increasing the dilution to 

 100 cm3 is shown. 



