2o6 



Journal of Agricultural Research 



Vol. III. No. 3 



sulphocyanate; acidity, equivalent to 0.002 gm. of Clj from hydro- 

 chloric acid; ammonia, none with Nessler's reagent. The dialyzed-iron 

 preparation after dilution was dialyzed for 24 hours with a parchment 

 membrane without any iron appearing in the dialyzate. 



While no soluble or ionized iron appeared in these tests we must assume 

 that some existed in the dialyzed-iron preparation because of the high 

 chlorin content. The nonappearance of iron in the dialyzate after dialysis 

 and in the filtrate after salting out the iron was probably due to adsorption 

 by the colloid or precipitate and to the strong hydrolysis that dilute ferric 

 chlorid undergoes.' From the chlorin content it appears that about one- 

 twelfth of the iron could have been present as ferric chlorid, but we can 

 hardly assume that it was there as such or that a certain quantity of 

 ferric chlorid in a colloidal-iron solution would act the same as in a simple 

 aqueous solution. We can simply assume that the soluble iron bore some 

 proportion to the quantity of chlorin. In the following tests, then, a low 

 availability of the dialyzed-iron preparation is not proof of the assimila- 

 tion of colloidal iron. 



RESULTS OF EXPERIMENTS 



Experiment I. — In a preliminary test the plants were grown for 42 

 days. The dialyzed iron was used at the rate of 10.5 parts of Fe per 

 100,000 parts of water for the first 10 days and at the rate of 1.05 parts 

 of Fe per 100,000 for the remaining 32 days. The ferric chlorid was used 

 at the rate of 0.41 part of Fe per 100,000. The results are given in 

 Table I. 



Table I. — Growth of rice with dialyzed iron and ferric chlorid — Experiment I 



The preparation of dialyzed iron had a certain availability, but rela- 

 tively large amounts were less effective than the smaller quantity of 

 ferric chlorid. 



Experiment II. — In a second experiment the dialyzed iron and 

 ferric chlorid were both used to furnish 0.4 gm. of Fe per 100,000 c. c. 

 of water. The plants were grown for 59 days. The results are given 

 in Table II. 



' This was borne out by the following test: To i c. c. of dialyzed iron 0.00275 gm. of Fe from FeCb was 

 added; the solution was made to 100 c. c. and the colloidal iron salted out by KsSO*. The filtrate, tested 

 for soluble iron (colorimetric method with KSCX), showed 0-00245 gm. of Fe had been lost. Of the 

 O.0O24S gm. of Fe lost 0.00056 gm. was lost by adsorption by the precipitate. Precipitation by hydrolysis 

 by water alone caused a loss of 0.00023 gm. of Fe, and hydrolysis in the presence ol K2S04 caused a loss of 

 0.001S9 gra, of Fe. 



