292 Gooch and Moseley — Detection and Approximative 



I. 



II. Difference. 



4357 



4364 



•0007 + 



■3551 



3559 



•0008 + 



2552 



2550 



•0002 — 



2898 



2890 



•0008 — 



1590 



1599 



•0009 + 



3528 



3534 



0006 + 



4498 



4494 



•0004 — 



5086 



5085 



■0001 — 



4462 



4457 



•0005 — 



4226 



4222 



•0004 — 



5170 



5165 



0005 — 



These results show that the standard of potassium perman- 

 ganate as determined from pure iron differs very slightly from 

 that obtained with the ammonium oxalate, but the standard 

 obtained in the former way would under ordinary conditions 

 be more satisfactory for work in iron analysis than the latter. 

 A simple and rapid method, then, for standardizing the potas- 

 sium permanganate solution would be to determine its strength, 

 first, by comparison with electrolytic iron in the manner above 

 described, and then by immediate titration with ferric chloride 

 to determine the exact amount of iron in each cubic centimeter 

 of the latter solution. This being ascertained, the ferric chlo- 

 ride solution can be employed at any time for the standardiza- 

 tion of potassium permanganate. 



Aet. XLT. — The Detection and Approximative Estimation 

 of Minute Quantities of Arsenic in Copper ; by F. A. 

 Gooch and H. P. Moseley. 



[Contributions from the Kent Chemical Laboratory of Tale College. — XXXVL] 



Sanger's recent successful application of the Berzelius- 

 Marsh process to the quantitative determination of arsenic in 

 wall-papers and fabrics,* by the comparison of test mirrors 

 with standard mirrors carefully prepared under the conditions 

 of the test, opens the way, naturally, to the similar estimations 

 of minute amounts of arsenic in any substances which may be 

 submitted to the process immediately or after suitable prepara- 

 tion. 



The need of a rapid and at the same time trustworthy method 

 for the determination of traces of arsenic in copper has led us 

 to a study of the application of Sanger's process to this special 

 case. 



* Am. Chem. Jour., xiii, 431. 



