(b) Chemical Examination.—Some of the chemical properties of roasted coffee afford fairly reliable means for the detection of an admixture of chicory. Coffee ash dissolves in water to the extent of about 80 per cent.; of the ash of roasted chicory only about 35 per cent. is soluble. Coffee ash is almost free from silica and sand, which substances form a notable proportion of the constituents of the ash of chicory.
The following (see p. [36]) are the results obtained by the writer from the analysis of the ash of coffee and chicory.
It will be observed from these analyses, that the most distinctive features presented by coffee ash are the absence of soda, and the small amounts of chlorine, ferric oxide and silica present. In these respects, it is very different from the ash of chicory. The proportion of phosphoric acid found in the latter is in excess of that given by some authorities. Several analyses of chicory ash have been made by the author, and, in every instance, the amount of phosphoric acid was over 8 per cent.; in one sample of the ash of commercial chicory it approximated 13 per cent.
| Java Coffee. | Chicory Root | |
| per cent. | per cent. | |
| Percentage of ash | 3·93 | 4·41 |
| Potassa | 53·37 | 23·00 |
| Soda | .. | 13·13 |
| Lime | 5·84 | 9·40 |
| Magnesia | 9·09 | 5·88 |
| Alumina | 0·43 | .. |
| Ferric oxide | 0·53 | 5·00 |
| Sulphuric acid | 3·19 | 9·75 |
| Chlorine | 0·78 | 4·93 |
| Carbonic acid | 15·26 | 4·01 |
| Phosphoric acid | 11·26 | 8·44 |
| Silica and sand | 0·25 | 16·46 |
| 100·00 | 100·00 |
Blyth gives the annexed table, showing the characteristic differences between coffee and chicory ash:[13]—
| Coffee Ash. | Chicory Ash. | |
| per cent. | per cent. | |
| Silica and sand | none | 10·69 to 35·88 |
| Carbonic acid | 14·92 | 1·78 „ 3·19 |
| Ferric oxide | 0·44 to 0·98 | 3·13 „ 5·32 |
| Chlorine | 0·26 „ 1·11 | 3·28 „ 4·93 |
| Phosphoric acid | 10·00 „ 11·00 | 5·00 „ 6·00 |
| Total soluble ash | 75·00 „ 85·00 | 21·00 „ 35·00 |
The following formula has been suggested for determining the percentage of pure coffee, in mixtures:—
C = 2 (100S - 174)3
where S represents the percentage of soluble ash.
Another noteworthy difference between roasted coffee and chicory, is the amount of sugar contained. As a rule, in roasted coffee, it ranges from 0·0 to 1·2 per cent.; in roasted chicory, it varies from 12· to 18· per cent. The quantity of sugar in a sample can be determined by Fehling’s method as follows:—