105 



ol nialciial is approxinuitcly equal to 1000 i)arls per 

 inillion of soil, 9 grams, to r)00 parts, and so on. For 

 llu' small |)ols conlaininii; only 20 pounds of soil, hall" 

 of llu'sc (juanlilics were usctl so as to gel the same ratios 

 that were used lor the large pots. In all cases, the crops 

 were planted on the same day that the various treat- 

 ments were ai)i)lied. From time to lime, the pots were 

 watered with lap water so as to maintain a sullicient 

 supply; hut no attempt was made to maintain a defi- 

 nite weight in Ihc several pots. 



Special Chemicals Used. 



All of the special reagents used in this work were 

 prc^pared hy E. Merck & Co., with the exception of pyri- 

 dine and dihydroxystearic acid, which were Kahlhaum 

 products. The required amounts of all compounds 

 were weighed out on chemical balances, for the experi- 

 ments conducted the first year; however, only the solid 

 conq)ounds were weighed, for the work of the second 

 year, becaiLse of the difficult}^ involved in weighing 

 exact quantities of liquids. The liquids were measured, 

 rather than weighed, one cubic centimeter being as- 

 sumed to weigh one gram; this assumption is not exact, 

 though it is sutlicienlly close for the purposes of the 

 work in hand. 



Soils Tested. 



Four different soils were used in the experiments 

 which were begun in 1913. The heaviest of the four, 

 classed as Cecil clay by the Bureau of Soils, is a rather 

 heavy, sticky, red clay. The area from which our sup- 

 ply came had not been in cultivation for a year or two, 

 and had grown up in lespedeza, weeds, and a few small 

 bushes. The lightest and poorest, classed as Cecil sand, 

 is a very ])oor, open, dry sandy soil. Our supply came 

 from a field which had grown a very poor crop of corn 

 during the summer of 1913. Two samples of Norfolk 

 sandy loam were used; one was taken from a rather 

 poor field about a mile south of the Experiment Sta- 

 tion farm, while the other w^as obtained from the most 

 productive part of the Experiment Station farm. The 

 soil samples were spread in a thin layer on a concrete 

 floor and stirred frequently until they became well 

 dried. After the drying, samples of 20 pounds, or 10 

 pounds, as the size of the pot required, were weighed 



