Oct. 14, 1918 Fertilizer Potash Residues in Hagerstown Silty Loam 63 



salt with hot water, and again weighing, after drying at 100° C, the 

 crucible with its felt and any residual, insoluble impurities, of which 

 a small amount always appeared. The difference between the two 

 weights thus obtained was counted as the weight of potash salt. This 

 procedure was used in all other potash determinations here reported. 

 The results of eight determinations of total potash for each plot were: 



Per cent. 



Plot I, untreated 3. 82i±o. 0240 



Plot 4, potash dressed 3. 54^ j; . 0134 



The fact, curious at first blush, appears that the potash-treated plot 

 contains at this time actually less potash than the untreated plot. The 

 probable explanation of this condition is found in the rather high, natural 

 variability in composition of the soils of the general series of plots, 

 which has been established by other studies of these soils (4, p. 187). 



POTASH SOLUBLE IN HOT, STRONG HYDROCHLORIC ACID 



The method followed was substantially the old official method ^ as 

 prescribed for cases in which only the alkalis are to be determined — 

 that is, 10 gm. of the air-dry fine soil in its natural condition of sub- 

 division were exposed for 10 hours on steam cups or in water bath to the 

 solvent action of 100 cc. of hydrochloric acid (1.115 sp. gr.), with hourly 

 shaking. The heavy metals and alkaline earths were thrown out of the 

 solution by barium hydrate, and the excess of this precipitant was 

 removed from the filtrate as oxalate. Each of the precipitates was 

 washed with from 600 to 700 cc. of warm water to insure the complete 

 recovery of the alkalis therefrom. All subsequent details of procedure 

 designed for determining the sodium in the solution were omitted. 



It is a matter of common experience that, of all the more abundant 

 soil elements, potassium reacts most sensitively to the conditions of acid 

 solution. Hilgard (6, p. J42) has emphasized this fact, and Frear and 

 White (4, p. 187) have demonstrated it for the potash m the soils of the 

 general fertilizer tract. 



The temperature condition is especially influential upon the rate of 

 solution for this constituent. In the first set of these determinations 

 the dissolving flasks were heated on steam cups. While the solutions 

 obtained gave in most cases fairly concordant duplicates, in others the 

 differences between duplicates were equal to fully 20 per cent of the 

 potash dissolved. These differences are attributed to inequalities of 

 the temperatures maintained on the different cups, and in part also 

 to the differences in the agitation of the liquids on different cups. 



Anothet set of determinations was made later, in which the dissolving 

 flasks, provided as in the former set with reflux condensers, were sus- 



' Report op Committes on Editimg Tb."*tativ8 and Official Methods of Analysis [.\ssoaA- 

 TioN of Official Agricultural Chemists], p. 24-25. 1916. 



