COFFEE 881 



while the twin beans are separated from each other. These beans then fall upon a 

 sieve, which allows the skin and the pulp to pass through, while the hard beans accu- 

 mulate and are progressively slid over the edge into baskets. They are next steeped 

 for a night in water, thoroughly washed in the morning, and afterwards dried in the 

 sun. They are now ready for the peeling mill, a wooden edge-wheel turned verti- 

 cally by a horse yoked to the extremity of its horizontal axis. In travelling over the 

 coffee, it bursts and detaches the coriaceous or parchment-like skin which surrounds 

 each hemispherical bean. It is then freed from the membranes by a winnowing 

 machine, in which four pieces of tin made fast to an axle are caused to revolve with 

 great velocity. Corn fanners would answer better than this rude instrument of negro 

 invention. The coffee is finally spread upon mats or tables, picked clean and packed 

 up for shipment. 



The most highly-esteemed coffee is that oftMocha. It has a smaller and a rounder 

 bean ; a more agreeable taste and smell than any other. Its colour is yellow. Next to 

 it in European reputation is the Martinique and Bourbon coffee ; its colour is greenish, 

 and it preserves almost always a silver grey pellicle, which comes off in the roasting. 

 The Bourbon coffee approaches nearest to the Mocha, from which it originally 

 sprung. The Saint Domingo coffee has its two extremities pointed, and is much less 

 esteemed then the preceding, 



The coffee-tree flourishes in hilly districts where its root can be kept dry, while its 

 leaves are refreshed with frequent showers. Eocky ground, with rich decomposed 

 mould in the fissures, agrees best with it. Though it would grow, as we have said, to 

 the height of 15 or 20 feet, yet it is usually kept down by pruning to that of 5 feet for 

 increasing the production of the fruit, as well as for the convenience of cropping. It 

 begins to yield fruit the third year, but is not in full bearing till the fifth, does not 

 thrive beyond the twenty-fifth, and is useless in general at the thirtieth. In the coffee 

 husbandry the plants should be placed 8 feet apart, as the trees throw out extensive 

 horizontal branches, and in holes 10 or 12 feet deep to secure a constant supply of 

 moisture. 



Coffee has been analysed by a great many chemists, with considerable diversity of 

 results. The best analysis perhaps is that of Schrader. He found that the raw beans 

 distilled with water in a retort communicated to it their flavour and rendered it turbid, 

 whence they seem to contain some volatile oil. On rebelling the beans, filtering, and 

 evaporating the liquor to a syrup, adding a little alcohol till no more matter was pre- 

 cipitated, and then evaporating to dryness, he obtained 17'58 per cent, of a yellowish- 

 brown transparent extract, which constitutes the characteristic part of coffee, though 

 it is not in that state the pure proximate principle, called caffeine. Its more remark* 

 able reaction is its producing, with both the protoxide and the peroxide salts of iron, a 

 fine grass-green colour, while a dark green precipitate falls, which re-dissolves when 

 an acid is poured into the liquor. It produces on the solution of the salts of copper 

 scarcely any effect, till an alkali be added, when a very beautiful green colour is pro- 

 duced which may be employed in painting. Coffee beans contain also a resin, and a 

 fatty substance somewhat like suet. According to Eobiquet, ether extracts from coffee 

 beans nearly 10 per cent, of resin and fat, but he probably exaggerates the amount. 

 The peculiar substance caffeine contained in the above extract is crystallisable. It 

 is remarkable in regard to composition, that after urea and the uric acid, it is among 

 organic products the richest in nitrogen. It was dissolved and described in 1820 by 

 Eunge. It does not possess alkaline properties. Pfaff obtained only 90 grains of 

 caffeine from six pounds of coffee beans. There is also an acid in raw coffee to which 

 the name of caffeic acid has been given. When distilled to dryness and decomposed, 

 it has the smell of roasted coffee. See CAFFEINE. 



Coffee undergoes important changes in the process of roasting. When it is toasted 

 to a yellowish brown it loses, according to Cadet, 12J per cent, of its weight, and is in 

 this state difficult to grind. When roasted to a chestnut brown it loses 18 per cent, j 

 and when it becomes entirely black, though not all carbonised, it has lost 23 per 

 cent. Schrader has analysed roasted coffee comparatively with raw coffee, and ha 

 found in the first 12 per cent, of an extract of coffee soluble in water and alcohol, 

 which possesses nearly the properties of the extract of the raw coffee, although it has 

 a deeper brown colour, and softens more readily in the air. He found also 10'4 of a 

 blackish brown gum ; 5'7 of an oxygenated extract, or rather apotbtme soluble in 

 alcohol, insoluble in water ; 2 of a fatty substance and resin ; 69 of burnt vegetable 

 fibre, insoluble. On distilling roasted coffee with water, Schrs$er obtained a product 

 which contained the aromatic principle of coffee ; it reddened litmus paper, and ex- 

 haled a strong and agreeable odour of roasted coffee. If we roast coffee in a retort, 

 the first portions of the aromatic principle of coffee condense into a yellow liquid in 

 the receiver ; and these may be added to the coffee roasted in the common way, from 

 which this matter has been expelled and dissipated in the air. 

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