THE ASH OF PLANTS. 149 



yses. Iq this way, it is believed, the real variations of 

 composition are pretty truly exhibited, independently of 

 the errors of analysis. 



The lowest and highest percentages are likewise given. 

 These are doubtless in many cases exaggerated by errors 

 of analysis, or by impurity of the material analyzed. 

 Chlorine and sulphuric acid are for the most part too low, 

 because they are liable to be dissipated in combustion, 

 while silica is often too high, from the fact of sand and soil 

 adhering to the plant. 



In two cases, single and perhaps incorrect analyses by 

 Bichon, which give exceptionally large quantities of soda, 

 are cited separately. 



A number of analyses that came to notice after making 

 out the averages, are given as additional. 



The following table includes both the kernel and straw 

 of Wheat, Rye, Barley, Oats, Maize, Rice, Buckwheat, 

 Beans, and Peas ; the tubers of Potatoes ; the roots and 

 tops of Sugar Beets, Field Beets, Carrots, Turnips, and 

 various parts of the Cotton Plant. 



For the average composition of other plants and vege- 

 table products, the reader is referred to a table in the ap- 

 pendix, p. 376, compiled by Prof Wolff", of the Royal 

 Agricultural Academy of Wurtemberg. That table in- 

 cludes also the averages obtained by Prof. Wolff for most of 

 the substances, cotton excepted, whose composition is rep- 

 resented in the pages immediately following. Any dis- 

 crepancies between Prof. Wolff's and the author's figures 

 are for the most part due to the use of fewer analyses by 

 the former. 



In both tables, the carbonic acid, which occurs in most 

 ashes, is excluded, from the fact that its quantity varies 

 according to the temperature at which the ash is pre- 

 pared. 



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