PREPARING FOR USE. 229 



Filtration — or " distilling". — By this process the cof- 

 fee is prepared in a " percolator," in which the ground 

 coffee is compressed between two metallic diaphragms, 

 so arranged as to permit the water to filter through it 

 slowly. This method often, but not always, yields a cup 

 of good coffee, as when the pouring of the boiling water 

 over the ground coffee is done slowly the drops in pass- 

 ing come in contact with too much air, the oxygen of 

 which makes a change in the aromatic particles, often 

 destroying them entirely. The extraction also is incom- 

 plete, for, instead of 20 per cent, the water by this pro- 

 cess dissolves only from 10 to 15 per cent, the balance 

 being lost by evaporation, while by the other methods 

 more than half the valuable parts of the coffee remain 

 in the grounds and is entirely lost. 



It is contended by many experts and connoisseurs that 

 to obtain the full aroma of coffee without extracting its 

 astringent properties, it must in all cases be prepared as 

 an infusion with boiling water, that is, " drawn " in the 

 same manner as tea, or simply allowed to reach the boil- 

 ing point after infusion, but no more. While others, 

 among whom is Baron Liebig, maintain that by simple 

 infusion alone much of the valuable soluble principle in 

 the coffee remains unextracted, being eventually thrown 

 out with the grounds. To avoid this unnecessary waste, 

 it is suggested that the grounds of the coffee once used by 

 infusion should be preserved, boiled and the liquor result- 

 ing therefrom be used for infusing a fresh supply. By 

 this method it is claimed that the substantial properties 

 of the previously infused coffee, and the aroma of the 

 new are obtained together in the fresh infusion. In many 

 French households the coffee grounds are utilized by dis- 

 tillation for economy's sake, hot water being poured over 

 them, which, after passing through, is preserved in a bottle 



