Methods of Analysis 229 



Part III.- APPENDIX 



METHODS OF ANALYSIS 

 With the Collaboration of E. E. Free and Dr. W. H. Ross 



Freedom of samples, especially vegetation, from contamina- 

 tion with adhering copper ; and accurate methods for determin- 

 ing minute amounts of copper in sediments, soils, waters and 

 vegetation, are vital to the integrity of the work recorded in 

 this publication. 



Unusual care was taken to perfect methods for preparation 

 of samples, especially roots grown in media containing copper; 

 and refined manipulation in the determination of copper reduced 

 the limit of error to approximately .00001 gram, or .01 milligram. 



Reagents and Apparatus 



Distilled ivater of three derivations was used: (1) University 

 of Arizona well water very slowly distilled through a block-tin 

 worm; (2) the same, redistilled from glass; and (3) University 

 of Arizona well water distilled from glass. 



Nitric and sulphuric acids from Baker & Adamson were used. 



Ammonia and H.S employed were passed through two wash 

 bottles. 



Blank determinations from time to time with reagents em- 

 ployed gave no trace of copper, thus insuring results obtained 

 by means of them. 



Copper was determined by electrolysis, in minute amounts 

 according to the manipulation of E. E. Free.^ 



The balance used was a No. 2112 Eimer and Amend short- 

 beam assay balance, "distinctly. sensitive to 1/200 milligram." 



Manipulation 



Ores and tailings. — 1-2 gms. were digested with a mixture of 

 8 c.c. HNO, and 5 c.c. HCl on a hot plate, then 4 c.c. HoSO^ added 

 and evaporated to HoSO^ fumes (method used in Old Dominion 

 laboratory at Globe, 'and Copper Queen at Bisbee). Took up 

 with water, filtered, neutralized with ammonia, then added 2 c.c. 

 H2SO4 and a few drops of ITNO.^ and electrolyzed. 

 Soils. — Soils were examined by two methods : 

 (a) 100 gms. soil was treated with a mixture of 80 c.c. HNO, 

 and 20 c.c. H.SO^ and digested in a porcelain disli on a hot plate 

 to sulphuric fumes ; digested with 200 c.c. water, filtered, washed 

 up to about 500 c.c, evaporated to 200 c.c. precipitated iron with 

 ammonia, filtered, washed with about 500 c.c. water, alkaline 

 filtrate reduced by evaporation, acidified faintly with HCl and 

 H,S passed for half an hour. The faint black precipitate was 



1 Electrolytic determination of minute quantities of copper, 12th Gen. 

 meeting Am." Electroehem. Soc, October 17-19, 1907. 



