532 AGRICULTURAL ANALYSIS 



equivalent amount of oxygen to the chlorin found must be sub- 

 tracted from the total. If an attempt be made to combine the 

 acid and basic elements, the chlorin should first be united with 

 sodium, and any excess thereof with potassium, and the amount 

 of base so combined calculated to oxid and deducted from the 

 total of such base or bases present. The carbonic acid present 

 should be combined first with alkalies after the chlorin has been 

 supplied. The phosphoric acid should be combined first with 

 the iron and afterwards with lime or magnesia. In all cases 

 the percentages should be based upon the ash, after the carbon 

 and sand have been deducted, or it is also convenient at times to 

 throw out of the results the carbon dioxid and to calculate the 

 other constituents to the ash free of that substance. In deter- 

 mining the quantities of mineral matters removed from soil by 

 crops, the ash should be determined with great care, freed of 

 carbon and sand, and the calculations made on the percentage 

 thus secured. In all statements of percentages of the essential 

 constituents of ash, as regards fertilizing materials, it should be 

 specified whether the percentage is calculated on a crude ash, 

 the pure ash, that is free of carbon and sand, or upon a basis 

 excluding the carbon dioxid. For the purpose of fertilizer control 

 the analyst and dealer will be satisfied, as a rule, with the deter- 

 mination of the percentages of phosphoric acid and potash alone. 

 To the other constituents of an ash is not assigned any commer- 

 cial value. 



450. Fertilizing Value of Ashes. Primarily, the fertilizing 

 value of wood-ashes depends on the quantity of plant food which 

 they contain. With the exception of lime, potash, and phosphoric 

 acid, however, the constituents of wood-ashes have little, if any, 

 commercial value. The beneficial effects following the applica- 

 tion of ashes, however, are greater than would be produced by the 

 same quantities of matter added in a purely manurial state. The 

 organic origin of these materials in the ash has caused them to 

 be presented to the plant in a form peculiarly suited for absorp- 

 tion. Land treated generally 'with wood-ashes becomes more 

 amenable to culture, is readily kept in good tilth, and thus 

 retains moisture in dry seasons and permits of easy drainage in 



