119 



TABLE 4. Comparison of modified and Smith methods for total potassium. 

 [Water-free basis.] 



tr.s not rrportril. 



b Too late to be included in the general average. 



Not included in the general average. 



MMENTS OP ANALYSTS. 



/'. E. Brawn: The magnesium nitrate method is undoubtedly quicker and easier of 

 manipulation than the |Kroxid fusion method. It has the advantage that there is 

 not nearly >u< h a large amount of silica to get rid of, as it was found necessary to dehy- 

 drate three or four times with the peroxid fusion method. Then, top, in the first oper- 

 ation of tin- iii-ion method there seems to be an uncertainty of reaction while avoiding 

 fu.-ioM, which is of course eliminated in the other method. 



You will notice from the results that the agreement is fair with a tendency for the 

 new method to giv slightly higher results. However, if the first determination in 

 Soil I by the fusion method is eliminated, the agreement is much better. On the 

 whole the magnesium nitrate method seems to me to be undoubtedly superior to the 

 other. 



\V. /'. Kdley: I find the magnesium nitrate method as outlined by you to be a very 

 simple and convenient scheme for determining the phosphoric acid in soils; and while 

 I have not had an opportunity to compare this method with others, I have no doubt 

 that the results are reliable. 



RECOMMENDATIONS. 



The work done this year, while not as extensive as the referee had wished, still 

 warrants in his opinion three conclusions, especially when it is remembered that work 

 along the same line last year and the year before is mainly concordant in the matter 

 of results: First, that the modified J. Lawrence Smith method for total potassium 

 compares very favorably with the regular method and is somewhat shorter; second, 



