EXPERIMENT TRIED ON COEFEE. 283 



and the thermometer were placed in quicksilver, 

 heated by an Argand lamp. 



It required a heat of between 450° to 470° of 

 Fahrenheit to produce any aroma, when the odour 

 increased rapidly. At about 370° the coffee had 

 not changed colour ; at 450° the aroma began to 

 form, and at 470° the coffee charred. It is fami- 

 liarly known that as coffee browns, and gives out 

 its odour, a fatty substance is formed. 



This experiment also shows that the art of roast- 

 ing coffee is a delicate art ; a difference of about 

 20° leaves it either raw and tasteless, or destroys 

 the aroma altogether. This may be one reason 

 why in England we so rarely meet with good coffee ; 

 whereas on the Continent the art of roasting and 

 making coffee is known to every common lackey : 

 still it must be remembered that coffee is the be- 

 verage of those countries ; and it is only fair to 

 the English to say, that on the Continent it is 

 as difficult to get boiling water for tea as it is to 

 procure good coffee in England. 



With respect to the principle on which the odour 

 of coffee depends, we find in Brande's Chemistry 

 that " Schrader endeavoured to ascertain the par- 

 ticular principle to which the flavour and aroma of 

 roasted coffee are due, by exposing each of the 

 proximate principles of unroasted coffee separately 

 to heat ; but he found that no one of them yielded 

 any peculiar flavour ; and that the ligneous residue 

 when roasted acquired as much of the characteristic 



