Oct. 29, 1921 A bsorption of Copper from the Soil by Potato Plants 283 



finally in distilled water. The vines were next dried for 16 hours in an 

 oven at 110° C. Separate analyses of leaves, stems, roots, and tubers 

 were made. 



Five or six tubers from each plot were thoroughly washed, rinsed in 

 distilled water, and dried with a towel. The tubers were pared, passed 

 through a grinder, well mixed, and transferred to a Mason jar with rubber 

 and top. Care is necessary in securing a uniform sample of the ground 

 tubers for analyses, as the water and solids separate very rapidly. 



Samples of soil were taken 6 inches deep, near the roots of the treated 

 plants, from the various plots at the time the plants were sampled. The 

 soil samples were held in Mason jars with rubbers and tops until analyzed. 

 Before analysis the stones and other foreign matter were removed from 

 the samples. 



DETERMINATION OF COPPER IN VINES AND TUBERS 



From 5 to 10 gm, of the dried leaves and stems, and from i to 5 gm. 

 of the roots were taken for copper analyses. The samples were ashed 

 in 4-inch porcelain dishes, 30 cc. of 5 per cent nitri acid were added, and 

 the whole was allowed to remain overnight. The solutions were filtered 

 and washed, after which ammonia was added to faint alkalinity. They 

 were brought to a boil, cooled, and made to volume, usually 150 cc. The 

 precipitated iron and alumina were removed by filtration, and an aliquot 

 of the filtrate was taken for the determination of copper. 



Table I. — Copper found in potato vines and tubers'^ 



Plants taken for analysis. 



Aug. 8.. 

 17- 



24. 



Sept. 3. 

 Average 



Parts analyzed. 



Leaves. 

 vStem.. . 

 Root... 

 Leaves . 

 Stem . . 

 Root... 

 Tubers. 

 Leaves. 

 Stem.. . 

 Root... 

 Tubers. 

 Leaves. 

 Stem . . 

 Root... 

 Leaves. 

 Stem . . . 

 Root.. . 

 Tubers. 



Control 

 plot. 



0017 

 o 

 0069 

 0027 

 0012 

 0002 



<» Analyses made on dry basis. 



