DETERMINATION OF ASH 7 



atmosphere of hydrogen or coal gas, although this precaution is 

 seldom required in other cases than that of the type mentioned 

 above. 



Percentages of Moisture in Plant Products. 

 In any particular case the percentage of moisture is to a 

 certain extent variable, depending upon soil, climatic conditions, 

 etc. 



5. Quantitative Determination of Ash. 



The determination of the percentage of mineral 

 constituents in plants is generally performed on the 

 dry matter obtained after the expulsion of moisture 

 (see 4, above). 



About 3 grams of the dry substance are weighed 

 out into a platinum basin which has been heated 

 to redness, cooled in the desiccator, and weighed. 

 The basin and its contents are then ignited over a 

 Bunsen flame for about five minutes, and are then 

 placed in a muffle furnace. The carbonaceous material 

 gradually burns away, and when no charred particles 

 remain, the basin is withdrawn, placed for a few 

 moments on an asbestos mat, then cooled in a desic- 

 cator, and weighed. The percentage of ash con- 

 stituents in the substance taken is then determined by 

 calculation. 



In many cases, however, especially in the case of 

 the seeds of cereals, the ash of which contains a large 

 proportion of salts of the alkali metals, and is readily 

 fusible, it is found to be a matter of some difficulty so 

 to adjust the temperature of the muffle that it is 

 sufficiently high to oxidise the organic matter 

 without fusing the mineral salts present. These salts, 



