August 1, 1864.] THE TECHNOLOGIST. 



CHEMICAL ANALYSIS OF COFFEE. 29 



increased bodily and mental activity involves increased consumption of 

 plastic material. 



Caffeine, on careful analysis, has been found to contain in 100 parts, 

 49-80 of carbon, 5-08 of hydrogen, 28-83 of nitrogen, and 16-29 of oxy- 

 gen. It is inodorous, but has a slightly bitter taste. The proportion in 

 which this principle is found to be present in coffee varies between fib. 

 and lflbs. in lOOlbs. of berries. 



The peculiar essential oil which is generated in coffee in the pro- 

 cess of roasting, by the action of heat upon some yet unascertained prin- 

 ciple contained in the berry, is also very similar to the volatile oil in 

 tea ; but the quantity of it in coffee appears to be comparatively very 

 small ; for whilst lOOlbs. of tea-leaves contain lib. of volatile oil, it 

 takes 500 cwts. of roasted coffee to give a similar quantity ; and yet it 

 is upon the presence of this oil that the flavour and value of the several 

 varieties of coffee mainly depend. 



The tannic acid is, by some chemists, also said to be generated only 

 in the process of roasting ; others maintain that it is present in the raw 

 bean. 



The chemical properties of the coffee-berry are altered by roasting, 

 and it loses about twenty per cent, of weight, but increases in bulk one- 

 third or one-half. Its peculiar aroma, and some of its other properties, 

 are due to a small quantity of essential oil, only one five-thousandth 

 part of its weight, which would be worth about 1001. an ounce in a sepa- 

 rate state. Coffee is less rich in theine than tea, but contains more 

 sugar and a good deal of cheese (casein). 



Schrader has analysed raw and roasted coffee, with the following 

 result : — 



Peculiar coffee principle 



Gum and mucilage 



Extractive . 



Eesin . 



Fatty oil 



Solid residue 



Loss 



Raw. 



Roasted 



17-58 



12-50 



3-64 



10-42 



0-62 



4-80 



0-41 ) 

 0-52} 



2-08 



66-66 



68-75 



10-57 



1-45 



100 



" The examination of coffee " observes Dr. F. Knapp, " has led to 

 interesting results, although they are still defective in pointing out the 

 quantitative composition of the berry." 



The following is the composition of the ash according to Live : — 



Potash 50-94 



Soda 14-76 



Lime 433 



Magnesia 10-90 



