Nov. 22, I9I5 Occurrence of Manganese in Wheat 351 



in the soil is about o.io per cent, calculated as elemental manganese. If 

 the manganese be an accidental constituent, as is usually held to be the 

 case, its presence must be due to the supply in our soil, but the amount 

 taken up appears to be very nearly constant, irrespective of the soil. 



In order to ascertain whether the manganese is universally present in 

 the wheat kernel and to determine in what quantity it is usually present, 

 I obtained samples of wheat from a number of localities in the United 

 States and Canada and from three European countries. While man- 

 ganese is probably present in every cultivated soil, it is very rarely the 

 case that it constitutes more than a small fraction of i per cent, while 

 iron is usually present in much more considerable quantities. The 

 amount of manganese present in the soil bears no relation to that of the 

 iron. In the soil on which our wheat samples were grown, the metallic 

 iron found by a mass analysis of the soil was a trifle over 30 times as 

 great as the total amount of manganese. The analytical results given 

 subsequently show that this is not the ratio in v.^hich the two elements 

 are present in the kernels and not even in the green plant or in the ripe 

 straw. It does not seem probable that the manganese has been absorbed 

 simply because it existed in the soil associated with iron, if this indeed 

 be the case in any strict sense, for the association might be with calcium 

 as well as with iron. 



The method used in determining manganese in grain was to take 

 10 gm. of ground, air-dried wheat, dissolve it in concentrated nitric acid, 

 and evaporate the solution to a thick, gummy, brown mass. This was 

 then heated over a free flame till all volatile matter was expelled. The 

 dish was then placed in a muffle and most of the carbon burned off. 

 After removal and cooling, a few (4 or 5) cubic centimeters of concen- 

 trated sulphuric acid were added. The sides of the dish were washed 

 down with a little water and the solution evaporated at last on a sand 

 bath till vapors of sulphuric acid escaped freely. After cooling, this was 

 taken up with water, boiled, and filtered into a 200 c. c. flask. The 

 residue on the filter was burned, taken up with a little sulphuric acid as 

 before, and the solution filtered and added to the first filtrate. The 

 combined filtrates should be about 150 c. c. in volume and contain about 

 5 per cent of sulphuric acid. A little silver sulphate (from 25 to 30 mgm.) 

 was next added and then 4 or 5 gm. of ammonic persulphate. The solu- 

 tion was placed on a boiling water bath and allowed to stand as long as 

 the color deepened. It was then cooled, made up to volume, and com- 

 pared with the standard, which had been prepared in the same way. 

 All reagents should be tested by making a blank. 



Manganese in the straw was determined in the same way, except that 

 the silica was removed by evaporating in a platinum dish with the addi- 

 tion of hydrofluoric acid. 



In Tables I and II are given the variety, the fertilizer applied, and 

 the percentage of iron and manganese found in wheat from Colorado and 



