This section is from the book "Beverages And Their Adulteration Origin, Composition, Manufacture, Natural, Artificial, Fermented, Distilled, Alkaloidal And Fruit Juices", by Harvey W. Wiley. Also available from Amazon: Beverages And Their Adulteration.
Coffee has a high content of mineral substances, and as these are largely soluble they give to the extracted coffee an additional value. Spencer found as the average of the composition of ash of four representative coffees, consisting of Mocha, Maracaibo, Java and Rio, the following data:
Sand..................................... | 1 .06 | percent |
Silica..................................... | 0.84 | percent |
Ferric Oxid............................... | 1.18 | percent |
Lime..................................... | 5.51 | percent |
Magnesia................................................................. | 10.98 | percent |
Potash ................................................................... | 61.84 | percent |
Soda..................................... | 0.36 | percent |
Phosphoric acid........................... | 12.94 | percent |
Sulphuric acid............................. | 4.63 | percent |
Chlorin.................................................................... | 0.76 | percent |
 
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